Distribution of PD-L1, TROP2 and HER2- "lowness" in early triple-negative breast cancer: an opportunity for treatment de-escalation

BACKGROUND

HER2, TROP2 and PD-L1 are novel targets in triple-negative breast cancer (TNBC). The combined expression status of these targets, and whether they can define prognostic subgroups, is currently undefined.

METHODS

Immunohistochemistry was used to determine HER2, TROP2 and PD-L1 levels in 459 TNBC cases, that received in the adjuvant/neoadjuvant setting active surveillance, CMF, anthracycline-, anthracycline plus taxane-, or carboplatin-containing regimes.

RESULTS

HER2-low patients with PD-L1 > 1 CPS (double-positive, herein "DP") had a mean PFS of 4768 days (95% CI: 4267-5268) versus 3522 days (95% CI: 3184-3861) for non-DP patients (P = 0.002). Regarding the received adjuvant treatment, DP patients (versus non-DP) receiving anthracyclines plus taxanes exhibited a mean PFS time of 4726 (95% CI: 4022-5430) versus 3302 (95% CI: 2818-3785) days (P = 0.039). Finally, 100% of DP patients that received a carboplatin-based regimen were long-term disease-free.

CONCLUSIONS

Early HER2-low, PD-L1-positive TNBC patients have a very good prognosis, particularly if treated with anthracycline/taxane- or carboplatin-containing regimes.

Updated progression-free survival and final overall survival with maintenance olaparib plus bevacizumab according to clinical risk in patients with newly diagnosed advanced ovarian cancer in the phase III PAOLA-1/ENGOT-ov25 trial

OBJECTIVE

In the PAOLA-1/ENGOT-ov25 trial (NCT02477644), adding maintenance olaparib to bevacizumab provided a substantial progression-free survival benefit in patients with newly diagnosed advanced ovarian cancer and homologous recombination deficiency (HRD)-positive tumors, irrespective of clinical risk. Subsequently, a clinically meaningful improvement in overall survival was reported with olaparib plus bevacizumab in the HRD-positive subgroup. We report updated progression-free survival and overall survival by clinical risk and HRD status.

METHODS

Patients in clinical response after first-line platinum-based chemotherapy plus bevacizumab received maintenance olaparib (up to 24 months) plus bevacizumab (up to 15 months in total) or placebo plus bevacizumab. This post hoc analysis evaluated 5-year progression-free survival and mature overall survival in patients classified by clinical risk and HRD status.

RESULTS

Of 806 randomized patients, 74% were higher-risk and 26% were lower-risk. In higher-risk HRD-positive patients, the hazard ratio (HR) for progression-free survival was 0.46 (95% confidence interval (95% CI) 0.34 to 0.61), with 5-year progression-free survival of 35% with olaparib plus bevacizumab versus 15% with bevacizumab alone; and the HR for overall survival was 0.70 (95% CI 0.50 to 1.00), with 5-year overall survival of 55% versus 42%, respectively. In lower-risk HRD-positive patients, the HR for progression-free survival was 0.26 (95% CI 0.15 to 0.45), with 5-year progression-free survival of 72% with olaparib plus bevacizumab versus 28% with bevacizumab alone; and the HR for overall survival was 0.31 (95% CI 0.14 to 0.66), with 5-year overall survival of 88% versus 61%, respectively. No benefit was seen in HRD-negative patients regardless of clinical risk.

CONCLUSION

This post hoc analysis indicates that in patients with newly diagnosed advanced HRD-positive ovarian cancer, maintenance olaparib plus bevacizumab should not be limited to those considered at higher risk of disease progression. Five-year progression-free survival rates support long-term remission and suggest an increased potential for cure with particular benefit suggested in lower-risk HRD-positive patients.

Safety of bevacizumab and olaparib as frontline maintenance therapy in advanced ovarian cancer: expert review for clinical practice

Olaparib, a poly(ADP-ribose) polymerase inhibitor, in combination with the antiangiogenic agent bevacizumab, is approved as maintenance therapy for patients with newly diagnosed stage III or IV epithelial ovarian cancer who have homologous recombination deficient tumors with a deleterious or suspected deleterious BRCA mutation and/or genomic instability based on the long-lasting survival benefit observed in the PAOLA-1 trial. Despite treatment with olaparib and bevacizumab showing an acceptable safety profile, the rate of discontinuations due to adverse events was relatively high, and toxicity related to this regimen may restrict its clinical use. Proper management of olaparib/bevacizumab-related adverse events is important for the improvement of quality of life and maximization of the efficacy of maintenance therapy. Here, we summarize the safety results of the PAOLA-1 study, focusing on treatment discontinuation reasons and adverse event profiles. We sought to shed light on toxicity monitoring and prevention, providing concise recommendations for the clinical management of the most relevant side effects.

Atezolizumab plus bevacizumab and chemotherapy for metastatic, persistent, or recurrent cervical cancer (BEATcc): a randomised, open-label, phase 3 trial

BACKGROUND

The GOG240 trial established bevacizumab with chemotherapy as standard first-line therapy for metastatic or recurrent cervical cancer. In the BEATcc trial (ENGOT-Cx10-GEICO 68-C-JGOG1084-GOG-3030), we aimed to evaluate the addition of an immune checkpoint inhibitor to this standard backbone.

METHODS

In this investigator-initiated, randomised, open-label, phase 3 trial, patients from 92 sites in Europe, Japan, and the USA with metastatic (stage IVB), persistent, or recurrent cervical cancer that was measurable, previously untreated, and not amenable to curative surgery or radiation were randomly assigned 1:1 to receive standard therapy (cisplatin 50 mg/m2 or carboplatin area under the curve of 5, paclitaxel 175 mg/m2, and bevacizumab 15 mg/kg, all on day 1 of every 3-week cycle) with or without atezolizumab 1200 mg. Treatment was continued until disease progression, unacceptable toxicity, patient withdrawal, or death. Stratification factors were previous concomitant chemoradiation (yes vs no), histology (squamous cell carcinoma vs adenocarcinoma including adenosquamous carcinoma), and platinum backbone (cisplatin vs carboplatin). Dual primary endpoints were investigator-assessed progression-free survival according to Response Evaluation Criteria in Solid Tumours version 1.1 and overall survival analysed in the intention-to-treat population. This study is registered with ClinicalTrials.gov, NCT03556839, and is ongoing.

FINDINGS

Between Oct 8, 2018, and Aug 20, 2021, 410 of 519 patients assessed for eligibility were enrolled. Median progression-free survival was 13·7 months (95% CI 12·3-16·6) with atezolizumab and 10·4 months (9·7-11·7) with standard therapy (hazard ratio [HR]=0·62 [95% CI 0·49-0·78]; p<0·0001); at the interim overall survival analysis, median overall survival was 32·1 months (95% CI 25·3-36·8) versus 22·8 months (20·3-28·0), respectively (HR 0·68 [95% CI 0·52-0·88]; p=0·0046). Grade 3 or worse adverse events occurred in 79% of patients in the experimental group and in 75% of patients in the standard group. Grade 1-2 diarrhoea, arthralgia, pyrexia, and rash were increased with atezolizumab.

INTERPRETATION

Adding atezolizumab to a standard bevacizumab plus platinum regimen for metastatic, persistent, or recurrent cervical cancer significantly improves progression-free and overall survival and should be considered as a new first-line therapy option.

FUNDING

F Hoffmann-La Roche.

Analysis of Tumor Microenvironment Changes after Neoadjuvant Chemotherapy with or without Bevacizumab in Advanced Ovarian Cancer (GEICO-89T/MINOVA Study)

PURPOSE

The aim of our study was to elucidate the impact of bevacizumab added to neoadjuvant chemotherapy (NACT) on the tumor immune microenvironment and correlate the changes with the clinical outcome of the patients.

EXPERIMENTAL DESIGN

IHC and multiplex immunofluorescence for lymphoid and myeloid lineage markers were performed in matched tumor samples from 23 patients with ovarian cancer enrolled in GEICO 1205/NOVA clinical study before NACT and at the time of interval cytoreductive surgery.

RESULTS

Our results showed that the addition of bevacizumab to NACT plays a role mainly on lymphoid populations at the stromal compartment, detecting a significant decrease of CD4+ T cells, an increase of CD8+ T cells, and an upregulation in effector/regulatory cell ratio (CD8+/CD4+FOXP3+). None of the changes observed were detected in the intra-epithelial site in any arm (NACT or NACT-bevacizumab). No differences were found in myeloid lineage (macrophage-like). The percentage of Treg populations and effector/regulatory cell ratio in the stroma were the only two variables significantly associated with progression-free survival (PFS).

CONCLUSIONS

The addition of bevacizumab to NACT did not have an impact on PFS in the GEICO 1205 study. However, at the cellular level, changes in CD4+, CD8+ lymphocyte populations, and CD8+/CD4+FOXP3 ratio have been detected only at the stromal site. On the basis of our results, we hypothesize about the existence of mechanisms of resistance that could prevent the trafficking of T-effector cells into the epithelial component of the tumor as a potential explanation for the lack of efficacy of ICI in the first-line treatment of advanced epithelial ovarian cancer. See related commentary by Soberanis Pina and Oza, p. 12.

Efficacy and Safety of Trastuzumab Deruxtecan in Patients With HER2-Expressing Solid Tumors: Primary Results From the DESTINY-PanTumor02 Phase II Trial

PURPOSE

Trastuzumab deruxtecan (T-DXd) is a human epidermal growth factor 2 (HER2)-directed antibody-drug conjugate approved in HER2-expressing breast and gastric cancers and HER2-mutant non-small-cell lung cancer. Treatments are limited for other HER2-expressing solid tumors.

METHODS

This open-label phase II study evaluated T-DXd (5.4 mg/kg once every 3 weeks) for HER2-expressing (immunohistochemistry [IHC] 3+/2+ by local or central testing) locally advanced or metastatic disease after ≥1 systemic treatment or without alternative treatments. The primary end point was investigator-assessed confirmed objective response rate (ORR). Secondary end points included safety, duration of response, progression-free survival (PFS), and overall survival (OS).

RESULTS

At primary analysis, 267 patients received treatment across seven tumor cohorts: endometrial, cervical, ovarian, bladder, biliary tract, pancreatic, and other. The median follow-up was 12.75 months. In all patients, the ORR was 37.1% (n = 99; [95% CI, 31.3 to 43.2]), with responses in all cohorts; the median DOR was 11.3 months (95% CI, 9.6 to 17.8); the median PFS was 6.9 months (95% CI, 5.6 to 8.0); and the median OS was 13.4 months (95% CI, 11.9 to 15.5). In patients with central HER2 IHC 3+ expression (n = 75), the ORR was 61.3% (95% CI, 49.4 to 72.4), the median DOR was 22.1 months (95% CI, 9.6 to not reached), the median PFS was 11.9 months (95% CI, 8.2 to 13.0), and the median OS was 21.1 months (95% CI, 15.3 to 29.6). Grade ≥3 drug-related adverse events were observed in 40.8% of patients; 10.5% experienced adjudicated drug-related interstitial lung disease (ILD), with three deaths.

CONCLUSION

Our study demonstrates durable clinical benefit, meaningful survival outcomes, and safety consistent with the known profile (including ILD) in pretreated patients with HER2-expressing tumors receiving T-DXd. Greatest benefit was observed for the IHC 3+ population. These data support the potential role of T-DXd as a tumor-agnostic therapy for patients with HER2-expressing solid tumors.

Cost-effectiveness of olaparib plus bevacizumab versus bevacizumab monotherapy in the maintenance of patients with homologous recombination deficiency-positive advanced ovarian cancer after response to first-line platinum-based chemotherapy

OBJECTIVE

The PAOLA-1 trial confirmed that adding olaparib to bevacizumab significantly increased clinical benefit following response to platinum-based chemotherapy in homologous recombination deficiency-positive ovarian cancer. The objective of this analysis was to determine the cost-effectiveness of olaparib plus bevacizumab compared with bevacizumab alone as maintenance treatment for patients with homologous recombination deficiency-positive advanced ovarian cancer from the Spanish National Health System perspective.

METHODS

A lifetime partitioned survival model with four health states (progression-free, post-progression 1, post-progression 2, and death) and monthly cycles was developed. Long-term survival, defined as 60 months, was included as a landmark to extrapolate progression-free survival from PAOLA-1. Weibull distribution was selected as the most accurate survival model for progression-free survival extrapolation. Time to second progression and overall survival were extrapolated using parametric survival models. Mortality was obtained from the overall survival and adjusted by Spanish women mortality rates. Health state utilities and utility decrements for adverse events were included. An expert panel validated data and assumptions. Direct costs (in 2021 euros (€)) were obtained from local sources and included drug acquisition and administration, subsequent therapies, monitoring costs, adverse events, and palliative care. A 3% annual discount rate was applied to costs and outcomes. The incremental cost-effectiveness ratio was calculated as cost per quality-adjusted life-years (QALYs) gained. Deterministic and probabilistic sensitivity analyses were performed.

RESULTS

Compared with bevacizumab alone, olaparib plus bevacizumab increased QALYs and life-years by 2.39 and 2.77, respectively, at an incremental cost of €58 295.31, resulting in an incremental cost-effectiveness ratio of €24 371/QALY. Probabilistic sensitivity analysis demonstrated that olaparib plus bevacizumab had a 49.5% and 90.3% probability of being cost-effective versus bevacizumab alone at a willingness-to-pay threshold of €25 000 and €60 000 per QALY gained, respectively.

CONCLUSION

For patients with homologous recombination deficiency-positive advanced ovarian cancer, olaparib plus bevacizumab is a cost-effective maintenance therapy compared with bevacizumab alone in Spain.

Digging into phenotype change in mismatch repair deficient endometrial carcinoma and treatment with immune checkpoint inhibition, a case report

•False negative cases for mismatch repair determination by immunohistochemistry may occur.•The mismatch repair phenotype in endometrial carcinoma impacts on therapeutic decision making.•Retesting for mismatch repair at relapse of endometrial carcinoma should be considered.

Analysis of the association of HER-2 low carcinomas and PAM50 assay in hormone receptor positive early-stage breast cancer

BACKGROUND

HER2-low has emerged as a new predictive biomarker in metastatic breast cancer. However, its prognostic value in early-stage carcinomas needs to be revisited. We aimed to evaluate the association of HER2-low carcinomas with PAM50 risk groups combined with clinicopathological variables in early breast cancer.

METHODS

We conducted a retrospective analysis of 332 patients with early-stage breast cancer that underwent PAM50 signature analysis between 2015 and 2021at Hospital Universitario 12 de Octubre (Madrid, Spain). Clinical and pathological variables were collected from medical records. After adjusting for potential confounders, we estimated Odds Ratio (OR) and 95% confidence interval for high-risk PAM50 subgroup, comparing HER2-low versus HER2-zero carcinomas by multivariable logistic regression. P values below 0.05 were deemed statistically significant.

RESULTS

192 (57%) patients were classified as HER2-low carcinomas. Median follow-up was 34 months. Adjusted OR for high-risk PAM50 when comparing HER2-low versus HER2-zero carcinomas was 1.31 (95% CI: 0.75-2.30, p = 0.33). The multivariable model detected significant associations for Ki-67% (≥20% vs. <20%: OR = 4.03, 95% CI: 2.15-7.56, p < 0.001), T staging category (T2/T3 vs. T1: OR = 3.44, 95% CI: 1.96-6.04, p < 0.001), progesterone receptor (PR ≥ 20% vs. <20%: OR = 0.44, 95% CI: 0.23-0.83, p = 0.01), nodal staging category (N+ vs. N0: OR = 3.8, 95% CI: 1.89-7.62, p < 0.001) and histological grade (grade 2 vs. 1: OR = 2.41, 95% CI: 1.01-5.73, p = 0.04; grade 3 vs 1: OR = 5.40, 95%CI: 1.98-14.60, p = 0.001).

CONCLUSIONS

In this early-stage breast cancer cohort, HER2-low was not associated with a high-risk PAM50 compared to HER2-zero carcinomas. Ki-67 ≥ 20%, T2/T3, histological grade 2/3, N+ and PR<20% were significantly associated to a high-risk PAM50.

Rucaparib for PARP inhibitor-pretreated ovarian cancer: A GEICO retrospective subgroup analysis from the Spanish Rucaparib Access Program

The poly(ADP-ribose) polymerase inhibitor (PARPi) rucaparib is approved as maintenance therapy for patients with platinum-sensitive recurrent high-grade ovarian cancer (HGOC). The efficacy and safety of rucaparib after PARPi therapy are largely unknown; therefore, we analyzed outcomes in the subgroup of PARPi-pretreated patients from Spanish hospitals participating in the Rucaparib Access Program. This post hoc subgroup analysis explored baseline characteristics, treatment exposure, safety, effectiveness, and subsequent therapy among women receiving rucaparib 600 mg twice daily after at least one prior PARPi for HGOC. Of 14 women eligible for the analysis, 11 (79%) had tumors harboring BRCA1/2 mutations. Patients had received a median of 5 (range 3-8) treatment lines before rucaparib. Twelve patients (86%) had previously received olaparib and two (14%) niraparib; 12 patients received rucaparib as treatment for platinum-resistant HGOC, one as treatment for platinum-sensitive HGOC, and one as maintenance therapy. Progression-free survival was 0.2-9.1 months. One of seven patients assessable for response by RECIST achieved stable disease. Adverse events occurred in 11 patients (79%; grade 3 in 29%), leading to treatment interruption in eight patients (57%), dose reduction in six (43%), but treatment discontinuation in only one (7%). No new safety signals were observed. This is one of the first reported series of real-world data on rucaparib after prior PARPi for HGOC. In this heavily pretreated population, rucaparib demonstrated meaningful activity in some patients and tolerability consistent with previous prospective trials. Future investigation should focus on identifying patients who may benefit from rucaparib after prior PARPi exposure.

Tumor P70S6K hyperactivation is inversely associated with tumor-infiltrating lymphocytes in triple-negative breast cancer

PURPOSE

Triple-negative breast cancer (TNBC) is characterized by large heterogeneity and relative lack of available targeted therapies. To find therapeutic strategies for distinct patients with TNBC, several approaches have been used for TNBC clustering, including recently immune and phosphoproteomic patterns. Based on 70-kDa ribosomal protein S6 kinase (P70S6K)-TNBC clustering, the current study explores the immune profiling in TNBC tumors.

METHODS

Stromal tumor-infiltrating lymphocytes (sTILs) were evaluated in human TNBC tumor samples. Furthermore, immunohistochemistry staining for CD8, CD4, Foxp3, and CD20 was performed in tissue microarrays (TMA) sections.

RESULTS

Histological analysis showed decreased sTILs, CD20⁺ cells, and CD8⁺/CD4⁺ ratio in high phosphorylated P70S6K (p-P70S6K) tumors. Moreover, p-P70S6K score was directly correlated with CD4⁺ and Foxp3⁺ T cells, while it was inversely correlated with CD8⁺/CD4⁺ and CD8⁺/Foxp3⁺ ratios.

CONCLUSION

sTIL infiltration and lymphocyte profiling vary in the context of hyperactivation of P70S6K in TNBC tumors.

Abstract P4-01-28: PALBOSPAIN: OBSERVATIONAL ANALYSIS OF FIRST-LINE THERAPY WITH PALBOCICLIB IN PATIENTS WITH HR+/HER2- METASTATIC BREAST CANCER (MBC) IN REAL-LIFE CONDITIONS

INTRODUCTION AND OBJECTIVES Palbociclib associated with hormone therapy (HT) has shown significant benefit in progression-free survival (PFS) and response rate versus HT alone in patients with HR+, HER2- MBC. The PALBOSPAIN study evaluates the efficacy and safety of palbociclib treatment under real-life conditions. The main objective of the study was to assess PFS, and secondary objectives were overall survival (OS), response rate, time to next line of treatment, percentage of dose reduction and safety.

MATERIAL AND METHODS This is an observational, ambispective, multicenter, nation-wide study. Patients diagnosed with HR+/HER2- MBC who had started first-line treatment with palbociclib between November 2017 and November 2019 were included. Patients treated within a clinical trial were excluded, as were those who had received any previous systemic treatment for advanced disease.

RESULTS 762 patients from 35 centers were included. 79% (n=600) were postmenopausal, 54.9% (n=418) had visceral disease, and 30.6% (n=233) had de-novo metastatic disease. Palbocliclib was combined with an aromatase inhibitor in 69.6% of patients and fulvestrant in 30.2% Four groups were established to assess efficacy (table 1): overall population; patients with de-novo metastatic disease (cohort A); patients relapsing &gt;12 months after the end of adjuvant hormonal therapy (cohort B); and patients relapsing within 12 months after the end of adjuvant hormonal therapy (cohort C). Median PFS was 24 months (CI 95%; 25-27) overall and 28 (IC 95%; 23-39), 29 (IC 95%;25-35) and 14 months (IC 95%;11-17) for cohorts a, B and C, respectively. Median overall survival was 42 months (40-NA). The most common side effects were neutropenia (71.3%, grade 3-4 in 52.5%, no episodes of febrile neutropenia), fatigue (38.6%), leucopenia (29.8%), anemia (28.9%), articular pain (19%), and thrombocytopenia (2,2%). 49% (n=385) of patients required dose reduction of palbociclib (one level in 27.6% and two levels in 21.4%).

CONCLUSION In the first two years after its approval in Spain, palbociclib in first line of HR+/HER2- MBC in real-life conditions yielded PFS and safety results comparable to those of PALOMA 2 and PALOMA 3 clinical trials. OS results were poorer, although the population included in this retrospective study is heterogeneous and median survival values have not been reached in some subgroups.

Table 1. Efficay results of palbociclib in real world

Citation Format: Noelia Martínez-Jáñez, Meritxell Bellet Ezquerra, Fernando Henao, Luis Manso, Antonio Antón, Pilar Zamora, Serafin Morales Murillo, Pablo Tolosa, Raquel Andrés, Lourdes Calvo, Elena Galve, Rafael Lopez, Francisco Ayala de la Peña, Sara López-Tarruella, Laia Boronat, Tamara Martos, J. Ignacio Chacón, Isabel Álvarez, Juan de la Haba-Rodríguez, Fernando Moreno Antón. PALBOSPAIN: OBSERVATIONAL ANALYSIS OF FIRST-LINE THERAPY WITH PALBOCICLIB IN PATIENTS WITH HR+/HER2- METASTATIC BREAST CANCER (MBC) IN REAL-LIFE CONDITIONS [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-01-28.

Abstract PD13-12: PD13-12 Imlunestrant, an oral selective estrogen receptor degrader, in combination with abemaciclib with or without an aromatase inhibitor, in estrogen receptor-positive advanced breast cancer: Results from the phase 1a/b EMBER study

Background: Imlunestrant is a novel, orally bioavailable selective estrogen receptor degrader (SERD) with pure antagonistic properties that result in sustained inhibition of estrogen receptor (ER)-dependent gene transcription and cell growth. Preclinically, imlunestrant has favorable efficacy and pharmacokinetic (PK) properties, including antitumor activity in ESR1-mutant models, along with enhanced efficacy when combined with abemaciclib. In dose escalation (Phase 1a) and dose expansion (Phase 1b) in the EMBER study, imlunestrant monotherapy was well tolerated with favorable safety, PK and encouraging antitumor activity in heavily pre-treated ER+, HER2- advanced breast cancer (aBC) patients (Jhaveri, ASCO 2022); imlunestrant recommended phase 2 dose (RP2D) was determined as 400mg QD. Here, we present the phase 1b dose expansion of imlunestrant with abemaciclib ± aromatase inhibitor (AI) in EMBER (NCT04188548).

Methods: Phase 1b enrolled patients with ER-positive (ER+), HER2-negative (HER2-) aBC [shown prior endocrine therapy (ET) sensitivity or untreated de novo aBC; ≤1 prior therapies for aBC but must not have received a prior CDK4/6 inhibitor]. Patients were randomized, based on menopausal status and presence of visceral metastases, to receive imlunestrant + abemaciclib OR imlunestrant + abemaciclib + AI. Men and premenopausal women received a concomitant GnRH agonist. Serial plasma samples were obtained for PK and ctDNA analysis. Key endpoints included safety and tolerability, PK, objective response rate (ORR) per RECIST v1.1 (ORR: complete response [CR] or partial response [PR]) in patients with measurable disease), and clinical benefit rate (CBR: CR or PR, or stable disease ≥24 weeks) in patients enrolled ≥24 weeks prior to data cut.

Results: As of 26 May 2022, 85 patients have received imlunestrant [n=80 at 400 mg (RP2D); n=5 at 800 mg] in combination with abemaciclib (150mg twice daily) ± AI. Forty-eight (56%) patients had visceral disease and 9% had at least 1 ESR1 mutation detected in ctDNA at baseline. Patients were predominantly (75%) ET pre-treated, 51% with an AI; and 8% and 5%, respectively, had received prior chemotherapy or fulvestrant, for aBC. The most common treatment-emergent adverse events were diarrhea (87%), nausea (58%), fatigue (45%), neutropenia (39%) and abdominal pain (34%). The majority of treatment-related AEs (TRAEs) were Grade 1 or 2, with Grade ≥3 TRAEs occurring in 36% of patients. Most common TRAEs at RP2D (400mg) were diarrhea (81%), nausea (45%), fatigue (33%) and neutropenia (35%). No patient discontinued treatment due to an AE. Dose reductions were required of both imlunestrant and abemaciclib in 6 (7%) patients and of either imlunestrant in 3 (4%) or abemaciclib in 22 (26%) patients. Preliminary efficacy is presented in Table 1.

Conclusion: Imlunestrant in combination with abemaciclib ± AI showed acceptable safety and tolerability, comparable to the MONARCH 2 trial of fulvestrant + abemaciclib, along with evidence of clinical activity in ER+, HER2- aBC patients. These data suggest no additive toxicity of imlunestrant when administered in combination with abemaciclib, along with comparable clinical benefit to that observed in MONARCH 2. Further data will be presented at the meeting. The phase 3, EMBER-3 study is ongoing; evaluating imlunestrant, investigator’s choice ET, and imlunestrant + abemaciclib in ET pre-treated ER+, HER2- aBC patients (NCT04975308).

Table 1. Preliminary efficacy in combination therapies in EMBER

Citation Format: Komal Jhaveri, Hwei-Chung Wang, Cynthia Ma, Elgene Lim, Jessica J. Tao, Luis Manso, Jean-Yves Pierga, Ritesh Parajuli, Yolanda Jerez Gilarranz, Yen-Shen Lu, Muralidhar Beeram, Tim Larson, Ajay Dhakal, Roohi Ismail-Khan, Claudia Karacsonyi, Shanshan Cao, Cynthia Osborne, Shawn T. Estrem, Bastien Nguyen, Yujia Li, Eunice Yuen. PD13-12 Imlunestrant, an oral selective estrogen receptor degrader, in combination with abemaciclib with or without an aromatase inhibitor, in estrogen receptor-positive advanced breast cancer: Results from the phase 1a/b EMBER study [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD13-12.

Real-world safety and effectiveness of maintenance niraparib for platinum-sensitive recurrent ovarian cancer: A GEICO retrospective observational study within the Spanish expanded-access programme

AIM

To describe patient characteristics, effectiveness and safety in a real-world population treated with niraparib in the Spanish expanded-access programme.

PATIENTS AND METHODS

This retrospective observational study included women with platinum-sensitive recurrent high-grade serous ovarian cancer who received maintenance niraparib within the Spanish niraparib expanded-access programme. Eligible patients had received ≥2 previous lines of platinum-containing therapy, remained platinum-sensitive after the penultimate line of platinum and had responded to the most recent platinum-containing therapy. Niraparib dosing was at the treating physician's discretion (300 mg/day fixed starting dose or individualised starting dose [ISD] according to baseline body weight and platelet count). Safety, impact of dose adjustments, patient characteristics and effectiveness were analysed using data extracted from medical records.

RESULTS

Among 316 eligible patients, 80% had BRCA wild-type tumours and 66% received an ISD. Median niraparib duration was 7.8 months. The most common adverse events typically occurred within 3 months of starting niraparib. Median progression-free survival was 8.6 (95% confidence interval [CI] 7.6-10.0) months. One- and 2-year overall survival rates were 86% (95% CI 81-89%) and 65% (95% CI 59-70%), respectively. Dose interruptions, dose reductions, haematological toxicities and asthenia/fatigue were less common with ISD than fixed starting dose niraparib, but progression-free survival was similar irrespective of dosing strategy. Subsequent therapy included platinum in 71% of patients who received further treatment.

CONCLUSION

Outcomes in this large real-world dataset of niraparib-treated patients are consistent with phase III trials, providing reassuring evidence of the tolerability and activity of niraparib maintenance therapy for platinum-sensitive recurrent ovarian cancer.

CLINICALTRIALS

GOV REGISTRATION

NCT04546373.

p27Kip1 V109G as a biomarker for CDK4/6 inhibitors indication in hormone receptor-positive breast cancer

CDK4/6 inhibitors benefit a minority of patients who receive them in the breast cancer adjuvant setting. p27Kip1 is a protein that inhibits CDK/Cyclin complexes. We hypothesized that single-nucleotide polymorphisms that impaired p27Kip1 function could render patients refractory to endocrine therapy but responsive to CDK4/6 inhibitors, narrowing the patient subpopulation that requires CDK4/6 inhibitors. We found that the p27Kip1 V109G single-nucleotide polymorphism is homozygous in approximately 15% of hormone-positive breast cancer patients. Polymorphic patients experience rapid failure in response to endocrine monotherapy compared with wild-type or heterozygous patients in the first-line metastatic setting (progression-free survival: 92 vs 485 days, P < .001); when CDK4/6 inhibitors are added, the differences disappear (progression-free survival: 658 vs 761 days, P = .92). As opposed to wild-type p27Kip1, p27Kip1 V109G is unable to suppress the kinase activity of CDK4 in the presence of endocrine inhibitors; however, palbociclib blocks CDK4 kinase activity regardless of the p27Kip1 status. p27Kip1 genotyping could constitute a tool for treatment selection.

Abstract P3-01-04: A real-world evidence study of everolimus plus endocrine therapy beyond CDK4/6 inhibitors for HR+/HER2- advanced breast cancer

Introduction Since the approval a decade ago of everolimus in combination with endocrine therapy (ET), the treatment landscape of metastatic breast cancer (mBC) has changed dramatically. Endocrine monotherapy after progression to CDK4/6 inhibitors has shown a limited progression-free survival (PFS) below 3 months. Evidence of the efficacy of everolimus plus ET after CDK4/6 inhibitors is scarce. Methods We performed a retrospective observational study of patients with mBC treated with everolimus between September 2011 and April 2022 in 4 Spanish hospitals. Clinical and demographic data were collected from medical records. Our main objective was to estimate the median progression-free survival (mPFS) for everolimus + ET in patients previously treated with a CDK4/6 inhibitor. We also collected the adverse events (AE) related to everolimus. Quantitative variables were summarized with medians (range), and qualitative variables with proportions. We used the Kaplan-Meier method for survival estimates. Results We identified a total of 297 mBC patients treated with everolimus plus ET. The median follow-up time was 20 months (interquartile range: 1 – 97 months). In this cohort, the median age at diagnosis was 49 years (26 – 84 years). At the moment of starting everolimus, the median number of previous lines of treatment was 2 (0 – 12), 22% of patients were ‘de novo’ metastatic, 67% presented visceral involvement, 40% had received previous chemotherapy for advanced disease, and 51% (n=152) had received a previous CDK4/6 inhibitor. The ET combined with everolimus was exemestane (77%), fulvestrant (18%), and tamoxifen (5%). 45% of patients were alive at data cut-off. In patients previously treated with a CDK4/6 inhibitor, the estimated median PFS (mPFS) was 5.9 months (95%CI: 5.0 – 7.8 months). In patients without visceral involvement (n=52), mPFS was 7.2 months (95%CI: 5.5 – 11.0 months), and 5.6 months (95%CI: 3.9 – 7.8 months) in the presence of visceral metastasis (n=100). In patients without previous chemotherapy in the metastatic setting (n=109), mPFS was 7.2 months (95%CI: 5.9 – 8.4 months), and 4.6 months (95%CI: 3.1 – 5.7 months) for patients who had received previous chemotherapy (n=43). For patients without a previous CDK4/6 inhibitor (n=145), the median PFS was 8.3 months (95%CI: 6.4 – 10.3 months). Everolimus starting doses were 10 mg (83%), 5 mg (15%), and 7.5 mg (2%). Dexamethasone mouthwash was used by 44% of patients. The most frequent AE were mucositis (51%; 3% grade 3), anemia (41%; 3% grade 3), hyperglycemia (34%; 2% grade 3), rash (28%; 2% grade 3), neumonitis (21%; 2% grade 3), and diarrhea (17%; 1% grade 3). There were no grade 4-5 adverse events. Dose reduction was made in 35% of patients, and in 16% of patients the treatment was discontinued due to toxicity. Conclusions In our cohort, the use of everolimus plus ET in mBC patients previously treated with a CDK4/6 inhibitor showed a clinically significant benefit in terms of PFS, especially in patients without visceral metastasis, and no previous chemotherapy for advanced disease. In this real-world study, the toxicity profile of everolimus was manageable.

Citation Format: Rodrigo Sánchez-Bayona, Manuel Alva, Alfonso López de sa, Yolanda Jerez Gilarranz, Ana Sánchez de torre, Pablo Tolosa, Alicia de luna, Sara López-Tarruella, Laura Lema, Fernando Moreno, Isabel Echavarria, Ainhoa Madariaga, Javier Benítez, Blanca Herrero, Macarena Rey, Justo Ortega, Salvador Gámez, Andrea Modrego, Rocío Martín Lozano, Luis Figuero-Pérez, Roberto Jiménez, Marta González Sevilla, Irene González, Marianela Bringas Beranek, María de toro, Tatiana Massarrah, María del Monte-Millán, Marina Pinardo, Luis Manso, Coralia Bueno-Muiño, José Ángel García-Sáenz, Miguel Martín, Eva Ciruelos. A real-world evidence study of everolimus plus endocrine therapy beyond CDK4/6 inhibitors for HR+/HER2- advanced breast cancer. [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-01-04.

Abstract OT1-03-06: Phase 1b/2 study of ladiratuzumab vedotin (LV) in combination with pembrolizumab for first-line treatment of triple-negative breast cancer (SGNLVA-002, trial in progress)

Background Patients with metastatic triple-negative breast cancer (mTNBC) have a poor prognosis. Treatment combinations of anti-programmed death protein 1 (anti–PD-1) agents with chemotherapy have shown promise in mTNBC. Ladiratuzumab vedotin (LV) is an investigational antibody-drug conjugate directed to LIV-1, a protein highly expressed on breast cancer cells, via a humanized IgG1 monoclonal antibody conjugated to approximately 4 molecules of monomethyl auristatin E (MMAE) by a protease-cleavable linker. LIV-1–mediated delivery of MMAE disrupts microtubules and induces cell cycle arrest and apoptosis. LV has also been shown to drive immunogenic cell death (ICD) to elicit an immune response. LV + pembrolizumab may result in synergistic activity through LV-induced ICD, creating a microenvironment favorable for enhanced anti–PD-1 activity. Interim results from an ongoing, multi-part, open-label study investigating the safety and efficacy of LV in patients with metastatic breast cancer (SGNLVA-001, NCT01969643), showed weekly LV monotherapy at doses up to 1.5 mg/kg were clinically active and generally well tolerated (Tsai 2021). Based on pharmacokinetic and pharmacodynamic modeling and simulation analysis, an intermittent LV + pembrolizumab dosing regimen is being evaluated to further enhance efficacy and improve the tolerability profile. Due to an unmet medical need for patients with unresectable locally advanced (LA)/mTNBC who are programmed death ligand 1 (PD-L1) low or negative, Part D will focus on this patient population. Trial Design SGNLVA-002 (NCT03310957) is an ongoing global single-arm, open-label phase 1b/2 study of LV + pembrolizumab as 1L therapy for patients with unresectable LA/mTNBC. Part D is currently enrolling ~40 patients. Eligible patients must have advanced disease with no prior cytotoxic/anti–PD-1 treatment, PD-L1 combined positive score &lt; 10, measurable disease per RECIST v1.1, and an ECOG performance status ≤1. Patients with Grade ≥2 pre-existing neuropathy or active central nervous system metastases are not permitted. Patients will receive LV at 1.5 mg/kg on Days 1 and 8 every 21 days plus pembrolizumab 200 mg on Day 1 q3w. The primary objectives are to evaluate the safety/tolerability and objective response rate of LV + pembrolizumab. Secondary objectives include duration of response, disease control rate, progression-free survival, and overall survival. Safety and efficacy endpoints will be summarized with descriptive statistics. Global enrollment is ongoing in the US, EU, and Asia.

Citation Format: Patrick Dillon, Reva Basho, Hyo S. Han, Hans-Christian Kolberg, Katherine Tkaczuk, George Zahrah, Maria Gion, Herman Voss, Jane Meisel, Timothy Pluard, Jenny Fox, Mafalda Oliveira, Ursa Brown-Glaberman, Erica Stringer-Reasor, Luis Manso, Sherko Küemmel, Lin Chi Chen, Sheng Wu, Brandon Croft, Valentina Boni. Phase 1b/2 study of ladiratuzumab vedotin (LV) in combination with pembrolizumab for first-line treatment of triple-negative breast cancer (SGNLVA-002, trial in progress) [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT1-03-06.

Abstract P5-02-28: p27Kip1 V109G single-nucleotide polymorphism (SNP): pinpointing the hormone-receptor positive breast cancer subpopulation that requires CDK4/6 inhibitors in addition to endocrine therapy

Background: CDK4/6 inhibitors benefit a limited percentage of hormone receptor-positive breast cancer (HRPBC) patients in the adjuvant setting: according to the MonarchE study, from all patients treated with the endocrine plus CDK4/6 inhibitor combination, 84% were adequately treated with endocrine therapy alone, ~5% experienced benefit from the combination, and 11% were not rescued from relapse by abemaciclib. Given the side effects and the cost, biomarkers to guide treatment decisions in this setting are appealing. We found that the p27Kip1 V109G SNP was enriched in HRPBC patients experiencing relapse despite endocrine treatment. p27Kip1 binds to cyclins and CDKs, restraining cells from cycling by inhibiting the formation of CDK/cyclin complexes and their kinase activity, resulting in less phosphorylation of Rb. A functionally impaired p27Kip1 could render tumor cells insensitive to endocrine therapy, while being rescued by CDK4/6 inhibitors. Thus, this SNP could narrow down the patient population that requires adjuvant CDK4/6 inhibitors. Methods: Isogenic HRPBC cell lines, wild-type or polymorphic homozygous for the p27Kip1 V109G SNP were generated with CRISPR-Cas9. Cell cycle and cell viability were assessed with BRDU incorporation and colony assays. Immunoprecipitation coupled with western blot (WB) was used to measure the formation of CDK/Cyclin complexes; Rb phosphorylation was assessed by WB. An in vitro kinase assay was set up to measure the CDK4 activity of p27Kip1/CDK/Cyclin complexes. Patients (n=115) with metastatic, HRPBC receiving endocrine monotherapy or in combination with CDK4/6 inhibitors were genotyped for the p27Kip1 V109G SNP, and PFS by genotype and therapy compared with the Kaplan-Meier method. All statistical tests were two-sided. Results: three isogenic polymorphic clones were generated from the wild-type T47-D hormone-positive cell line. The three clones were resistant to hormonal deprivation compared to wild-type cells. The relative plating efficiency (RPE) in the colony assays of the polymorphic clones exposed to hormonal deprivation compared to that of deprived T47-D cells was 550% (clone C1), 165% (clone E1) and 100% (Clone F5); P&lt; 0.005. The three clones were also resistant to fulvestrant (Fulv) (300%, 170% and 180%, respectively); P&lt; 0.005. Cell cycle (positive BRDU cells) decreased ~3 fold in wild type cells (18% to 6.5%) when exposed to hormonal deprivation or Fulv, but remained unaltered in the polymorphic clones. However, when palbociclib was added to hormonal deprivation or Fulv, the effects in RPE increased and were similar in polymorphic clones and parental cells (&gt;5% RPE compared to vehicle, both in polymorphic and wild-type cells). The p27Kip1 V109G SNP was found in homozygosity in ~15% of metastatic HRPBC patients. When patients received endocrine monotherapy in the first-line setting, polymorphic patients experience rapid failure (N=51) compared to wild-type/heterozygous patients (4.3 vs. 21.1 months; P &lt; 0.0001). However, when patients received hormonal plus CDK4/6 inhibitors, the differences disappeared (18.3 vs. 24.3 months; P=0.85). Mechanistically, we observed that the formation of CDK2/CyclinA, CDK2/CyclinE and CDK4/Cyclin D1 complexes was &gt;200% higher in polymorphic than in wild-type cells (P&lt; 0.05). Regarding CDK4 kinase activity of p27Kip1/CDK/Cyclin complexes, as opposed to wild-type p27Kip1, p27Kip1 V109G was unable to suppress the kinase activity of CDK4 in presence of Fulv or hormonal deprivation. However, palbociclib was able to fully suppress CDK4 kinase activity regardless of the p27Kip1 genotype. Conclusion: Germline p27Kip1 genotyping can constitute a tool for treatment selection: whereas wild-type patients are adequately treated with endocrine monotherapy, polymorphic patients are inherently resistant, but are rescued with CDK4/6 inhibitors. Thus, hormonal+CDK4/6 inhibitor combos could be reserved for the polymorphic patients.

Citation Format: Miguel Quintela-Fandino, Silvana Mouron, Maria J. Bueno, Manuel Muñoz, Raul Torres, Sandra Rodriguez, Rodrigo Sánchez-Bayona, Luis Manso, Jorge Silva, Marcos Malumbres. p27Kip1 V109G single-nucleotide polymorphism (SNP): pinpointing the hormone-receptor positive breast cancer subpopulation that requires CDK4/6 inhibitors in addition to endocrine therapy. [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-02-28.

Phosphoproteomic analysis of neoadjuvant breast cancer suggests that increased sensitivity to paclitaxel is driven by CDK4 and filamin A

Precision oncology research is challenging outside the contexts of oncogenic addiction and/or targeted therapies. We previously showed that phosphoproteomics is a powerful approach to reveal patient subsets of interest characterized by the activity of a few kinases where the underlying genomics is complex. Here, we conduct a phosphoproteomic screening of samples from HER2-negative female breast cancer receiving neoadjuvant paclitaxel (N = 130), aiming to find candidate biomarkers of paclitaxel sensitivity. Filtering 11 candidate biomarkers through 2 independent patient sets (N = 218) allowed the identification of a subgroup of patients characterized by high levels of CDK4 and filamin-A who had a 90% chance of achieving a pCR in response to paclitaxel. Mechanistically, CDK4 regulates filamin-A transcription, which in turn forms a complex with tubulin and CLIP-170, which elicits increased binding of paclitaxel to microtubules, microtubule acetylation and stabilization, and mitotic catastrophe. Thus, phosphoproteomics allows the identification of explainable factors for predicting response to paclitaxel.

Rucaparib in recurrent ovarian cancer: real-world experience from the rucaparib early access programme in Spain – A GEICO study

Background:

Rucaparib is a poly(ADP-ribose) polymerase inhibitor approved in Europe as maintenance therapy for recurrent platinum-sensitive (Pt-S) ovarian cancer (OC). The Rucaparib Access Programme (RAP) was designed to provide early access to rucaparib for the above-mentioned indication, as well as for patients with BRCA-mutated Pt-S or platinum-resistant (Pt-R) OC and no therapeutic alternatives.

Methods:

In this observational, retrospective study we analysed the efficacy and safety of rucaparib within the RAP in Spain. Hospitals associated with the Spanish Ovarian Cancer Research Group (GEICO) recruited patients with high-grade epithelial ovarian, fallopian tube, or primary peritoneal cancer treated with rucaparib 600 mg twice daily as maintenance or treatment (Pt-S/Pt-R) in the RAP. Baseline characteristics, efficacy, and safety data were collected.

Results:

Between July 2020 and February 2021, 51 patients treated in 22 hospitals in the RAP were included in the study. Eighteen patients with a median of 3 (range, 1–6) prior treatment lines received rucaparib as maintenance; median progression-free survival (PFS) for this group was 9.1 months (95% confidence interval [CI], 4.2–11.6 months). Among 33 patients (median 5 [range, 1–9] prior treatment lines) who received rucaparib as treatment, 7 and 26 patients had Pt-S and Pt-R disease, respectively. Median PFS was 10.6 months (95% CI, 2.5 months-not reached) in the Pt-S group and 2.2 months (95% CI, 1.1–3.2 months) in the Pt-R group. Grade ≥ 3 treatment-emergent adverse events were reported in 39% of all patients, the most common being anaemia (12% and 15% in the maintenance and treatment groups, respectively). At data cut-off, 5 patients remained on treatment.

Conclusion

Efficacy results in these heavily pre-treated patients were similar to those from previous trials. The safety profile of rucaparib in real life was predictable and manageable.

Modeling the Prognostic Impact of Circulating Tumor Cells Enumeration in Metastatic Breast Cancer for Clinical Trial Design Simulation

Despite the strong prognostic stratification of circulating tumor cells (CTCs) enumeration in metastatic breast cancer (MBC), current clinical trials usually do not include a baseline CTCs in their design. This study aimed to generate a classifier for CTCs prognostic simulation in existing datasets for hypothesis generation in patients with MBC. A K-nearest neighbor machine learning algorithm was trained on a pooled dataset comprising 2436 individual MBC patients from the European Pooled Analysis Consortium and the MD Anderson Cancer Center to identify patients likely to have CTCs ≥ 5/7 mL blood (StageIVaggressive vs StageIVindolent). The model had a 65.1% accuracy and its prognostic impact resulted in a hazard ratio (HR) of 1.89 (Simulatedaggressive vs SimulatedindolentP < .001), similar to patients with actual CTCs enumeration (HR 2.76; P < .001). The classifier's performance was then tested on an independent retrospective database comprising 446 consecutive hormone receptor (HR)-positive HER2-negative MBC patients. The model further stratified clinical subgroups usually considered prognostically homogeneous such as patients with bone-only or liver metastases. Bone-only disease classified as Simulatedaggressive had a significantly worse overall survival (OS; P < .0001), while patients with liver metastases classified as Simulatedindolent had a significantly better prognosis (P < .0001). Consistent results were observed for patients who had undergone CTCs enumeration in the pooled population. The differential prognostic impact of endocrine- (ET) and chemotherapy (CT) was explored across the simulated subgroups. No significant differences were observed between ET and CT in the overall population, both in terms of progression-free survival (PFS) and OS. In contrast, a statistically significant difference, favoring CT over ET was observed among Simulatedaggressive patients (HR: 0.62; P = .030 and HR: 0.60; P = .037, respectively, for PFS and OS).

Phase 1b/2 study of ladiratuzumab vedotin (LV) in combination with pembrolizumab for first-line treatment of triple-negative breast cancer (SGNLVA-002, trial in progress)

TPS1127

Background: Patients with metastatic triple-negative breast cancer (mTNBC) have a poor prognosis. Treatment combinations of anti-programmed death ligand 1 (anti–PD-L1) agents with chemotherapy have shown promise in mTNBC. LV is an investigational antibody–drug conjugate directed to LIV-1, a protein highly expressed on breast cancer cells, via a humanized IgG1 monoclonal antibody conjugated to monomethyl auristatin E (MMAE) by a protease-cleavable linker. LIV-1–mediated delivery of MMAE disrupts microtubules and induces cell cycle arrest and apoptosis. LV has also been shown to drive immunogenic cell death (ICD) to elicit an immune response. LV + pembrolizumab may result in synergistic activity through LV-induced ICD, creating a microenvironment favorable for enhanced anti–PD-L1 activity. Preliminary results show LV delivered once every 3 weeks (Q3W) + pembrolizumab was tolerable with encouraging antitumor activity in patients with mTNBC (Han 2019). Additionally, interim results of weekly LV monotherapy at doses up to 1.5 mg/kg were clinically active and generally well tolerated (Tsai 2021). Based on pharmacokinetic and pharmacodynamic modeling and simulation analysis, an intermittent LV + pembrolizumab dosing regimen is being evaluated to further enhance efficacy and improve the tolerability profile. Due to an unmet medical need for patients with mTNBC who are PD-L1 low or negative, Part D will focus on this patient population. Methods: SGNLVA-002 (NCT03310957) is an ongoing global single-arm, open-label phase 1b/2 study of LV + pembrolizumab as 1L therapy for patients with unresectable locally advanced/mTNBC. Part D is currently enrolling ̃40 patients. Eligible patients must have advanced disease with no prior cytotoxic/anti–PD-L1 treatment, PD-L1 combined positive score < 10, measurable disease per RECIST v1.1 and an ECOG score ≤1. Patients with Grade ≥2 pre-existing neuropathy or active central nervous system metastases are not permitted. Patients will receive LV at 1.5 mg/kg on Days 1 and 8 plus pembrolizumab 200 mg on Day 1 Q3W. The primary objectives are to evaluate the safety/tolerability and objective response rate of LV + pembrolizumab. Secondary objectives include duration of response, disease control rate, progression-free survival, and overall survival. Safety and efficacy endpoints will be summarized with descriptive statistics. Global enrollment is ongoing in the US, EU, and Asia. Clinical trial information: NCT03310957.

Clinical experience with rucaparib after prior PARPi treatment: A subanalysis from the rucaparib access program in Spain by GEICO

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Background: Rucaparib is a PARP inhibitor (PARPi) approved as maintenance therapy for platinum (Pt)-sensitive recurrent high-grade ovarian cancer (HGOC), and as treatment for BRCA-mutant HGOC patients. To date, there is little evidence about the efficacy and safety of rucaparib after prior exposure to PARPi. This subanalysis aims to describe the patients’ characteristics and treatment outcomes with rucaparib in women who were included in the rucaparib early access program (RAP) in Spain and had received a prior PARPi. Methods: A retrospective study was conducted by GEICO at 22 hospitals in Spain to analyze data of 51 women treated within the RAP (600 mg BID). Adult women with HGOC, fallopian tube, or primary peritoneal cancer, who had received at least one prior PARPi before rucaparib were analyzed. Patients’ characteristics, medical history, safety, efficacy, and dosing data were collected. Results: A total of 14 women, with a median age of 63 years old (42-78) were included in this subanalysis. Of them, 92.9% were diagnosed of epithelial ovarian cancer and 78.6% had mutations in BRCA1/ 2 genes. The median number of lines before rucaparib was 5 (3-8), while the number of lines before the first PARPi was 3 (2-5). Except for one woman who had received 2 prior PARPis before rucaparib, the others had received just 1. Most patients were given olaparib as the first PARPi (n = 12, 85.8%), while niraparib was the initial PARPi in the remaining cases (n = 2, 14.3%). The outcomes of the treatment with rucaparib in these patients are outlined in table 1. Rucaparib was given as maintenance therapy in 1 patient and as treatment in 13 patients, 12 of them being Pt-resistant. The progression-free survival (PFS) ranged from 0.23 to 9.12 months. Adverse events (AE) of any grade were detected in 78.6% of patients, whereas AE of grade ≥3 affected 28.6% of women. Rucaparib dose was interrupted in 57.1% and reduced in 42.9% of patients. Only 1 patient discontinued rucaparib due to toxicity. No new safety signals were detected. Conclusions: This is one of the first real-word studies reporting the use of rucaparib after treatment with another PARPi. Even in these heavily pre-treated patients who had received prior PARPi, rucaparib efficacy has been notable in some cases, and its safety profile is consistent with that reported in previous clinical trials. Future studies should focus on the selection of patients who could benefit from rucaparib after prior PARPi exposure. [Table: see text]

Clinical insights from the rucaparib access program in Spain: A sub-analysis of long-term responders by GEICO

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Background: Rucaparib is a PARP inhibitor approved for the treatment of high-grade ovarian cancer (HGOC). Clinical trials have demonstrated its benefit both as maintenance therapy (MTN) for platinum (Pt)-sensitive recurrent HGOC, and as treatment (Tx) in BRCA-mutated relapsed or recurrent HGOC patients. Here we analyze real-world data from the rucaparib early access program (RAP) in Spain with focus in the long-term responder patients (LTR). Methods: A retrospective observational study was performed by GEICO at 22 hospitals in Spain that had treated patients within the RAP. Adult women with HGOC, fallopian tube, or primary peritoneal cancer were included and received rucaparib (600 mg BID) in the MTN, Tx Pt-sensitive or Tx Pt-resistant setting. Patients’ characteristics, medical history, safety, efficacy, and dosing data were collected. In this analysis, long-term response was defined as progression-free survival (PFS) ≥12 months for the MTN group and ≥6 months for the Tx group. LTR were stratified based on the rucaparib indication (MTN/Tx). Results: Between July 2020 and February 2021, 51 patients were recruited: 18 received rucaparib as MTN and 33 as Tx. In the MTN group, 6 patients (33.3%) were LTR, with a median age of 65 years (54-79). Of them, 2 patients (33.2%) harbored BRCA or RAD51C mutations. The median number of prior lines was 3 (2-6), being ≥5 in 33.2%, and 50.0% received prior bevacizumab. ECOG PS was ≤1 in all these patients, 66.6% had measurable disease and 50.0% achieved a partial response to prior Pt-based chemotherapy. In the Tx group, 10 patients (30.3%) were LTR, with a median age of 71 years (47-86). All of them harbored BRCA and/or RAD51C mutations. The median number of prior lines was 6 (2-9), with 60.0% receiving ≥5 prior lines, and 50.0% received prior bevacizumab. Regarding Pt-status, 40.0% of patients were Pt-sensitive and 60.0% were Pt-resistant. The ECOG PS was ≥1 in 30.0% of patients and 60.0% had measurable disease. The median PFS of LTR was not achieved in the MTN group and was 10.9 months (95% CI: 7.0-16.7) in the Tx group. Adverse events (AE) of any grade were reported in 66.6% of LTR within the MTN group and in 100.0% within the Tx group, while AE of grade ≥3 occurred in 16.6% and 50.0%, respectively. Rucaparib dose was reduced in 50.0% of LTR in the MTN group and 80.0% in the Tx group. Discontinuation rate due to rucaparib toxicity was 20.0% in the Tx group and there were no discontinuations due to toxicity in the MTN group. No new safety signals were detected. At present, 3 and 1 patients are still receiving rucaparib as MTN and Tx, respectively. Conclusions: A durable response was achieved in a notable proportion of patients, even despite their unfavorable conditions at treatment initiation (heavily pre-treated patients, partial response or resistance to Pt, or high volume of disease). The safety profile of rucaparib in this real-world setting is consistent with that reported in clinical trials.

Cost-effectiveness of Olaparib plus Bevacizumab versus Bevacizumab in the maintenance of patients with HRD+ advanced ovarian cancer after response to first-line platinum-based chemotherapy in Spain

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Background: Olaparib, a poly (ADP-ribose) polymerase inhibitor (PARPi), monotherapy as first-line maintenance treatment has shown to be cost-effective in ovarian cancer (OC) patients with BRCA mutations in Spain. Regardless of BRCA status, patients with homologous recombination deficiency positive (HRD+) also benefit from PARPi following first-line platinum-based therapy. PAOLA-1 trial confirmed that adding Olaparib to bevacizumab (BEV) significantly increased progression-free survival (PFS) in OC patients. The aim of this study was to assess the cost-effectiveness of Olaparib plus BEV versus BEV monotherapy for the maintenance treatment of HRD+ advanced OC patients after response to first-line platinum-based therapy plus BEV from Spanish National Health System perspective. Methods: A lifetime partitioned survival model with monthly cycles and four health states (PFS, first progression, second progression, and death) was developed. Long-term survival defined as 60 months was included in the mixed survival model as a landmark to extrapolate PFS from the PAOLA-1 trial. Weibull distribution was selected as the most accurate survival model for PFS extrapolation. Time to second progression, and overall survival (OS) were extrapolated using parametric survival models. Mortality was obtained from the OS and adjusted by Spanish mortality rates. Health state utilities and adverse event (AE) frequencies were obtained from PAOLA-1. An expert panel validated data and assumptions. Direct costs including drug acquisition and administration, follow-up, subsequent therapies, AE, and end-of-life were obtained from local sources. A 3% annual discount rate was applied to costs and outcomes. The incremental cost-effectiveness ratio (ICER) was calculated as cost per quality-adjusted life-years (QALYs) gained. One-way and probabilistic sensitivity analyses (PSA) were performed to assess the robustness of the model. Results: Base-case analysis of Olaparib plus BEV compared with BEV showed an ICER of €24,371 per QALY gained. Discount rates applied to outcomes and the cost of Olaparib generated the most significant changes in the ICER. PSA demonstrated that Olaparib plus BEV had a 49.5% and 90.3% probability of being cost-effective versus BEV at a willingness-to-pay of €25,000 and €60,000 per QALY gained, respectively. Conclusions: Olaparib plus BEV is a cost-effective maintenance therapy compared with BEV for patients with HRD+ advanced OC in Spain.[Table: see text]

Abstract P5-13-24: Efficacy of first line CDK4/6 inhibitors in HER2-low vs HER2-zero, hormone receptor positive, HER2 negative metastatic breast cancer

Introduction: CDK4/6 inhibitors are the standard of care in the vast majority of patients with metastatic breast cancer (MBC) in first line setting. HER2-low expression, defined as IHC score of 1+ or 2+ with negative ISH assay, has been associated with resistance to CDK4/6 inhibitors. This has not yet been explored for advanced disease in the first line setting. We aimed to analyze the efficacy of CDK4/6 inhibitors in this subset of patients compared to HER2-zero tumors. Methods: We identified patients with positive hormone receptors and HER2 negative metastatic breast cancer treated with first line CDK4/6 inhibitor (palbociclib, ribociclib or abemaciclib) and letrozole or fulvestrant between December 2017 - April 2021 in our institution (Hospital 12 de Octubre, Madrid, Spain). HER2 expression and PAM50 subtypes were analyzed in metastatic tissue samples for all patients. For the analysis, patients were classified as HER2-zero or HER2-low groups. Our main objective was to evaluate the relationship between HER2 expression and progression-free survival (PFS) with log-rank test. Multivariable Cox regression model was used to estimate the adjusted hazard ratio (HR). As secondary objectives, we analyzed this association in all CDK4/6 subgroups and described the prevalence of PAM-50 subtypes in each category (HER2-low and HER2-zero). Results: We included 82 patients in our final analysis. 57% of the patients were classified in the HER2-low category. In our sample, 49% of patients received palbociclib, 39% ribociclib and 12% abemaciclib. A high proportion of patients presented visceral disease (75% in the HER2-zero vs 60% in the HER2-low group). Only 20% of tumors were considered as hormone-resistant. The overall response rate was slightly higher in the HER2-zero category (41% vs 35% in the HER2-low). With a median follow-up of 14 months (2 - 48 months), the median PFS was 31.7 months (95%CI: 20.3 - NR months) in the HER2-zero category and 22.8 months (95%CI: 15.7 - NR months) in the HER2-low (p=0.37). In the multivariable Cox regression model, HER2-low tumors were associated with a non-significantly higher risk of progression (HR=1.62; CI 95%:0.74-3.54). In patients treated with palbociclib, the median PFS for HER2-zero vs HER2-low categories were 31.7 months and NR (p=0.79), respectively. For ribociclib, the HER2-zero had a median PFS of 38.4 months and 33.1 months in the HER2-low category (p=0.47). In patients treated with abemaciclib, median PFS was NR for HER2-zero group and 9.2 months for HER2-low (p=0.18). The interaction test between HER2 categories and CDK4/6 inhibitors was not statistically significant (p=0.48). PAM-50 subtypes information was available for 47 patients. In these patients the prevalence of PAM-50 subtypes showed a relative higher proportion of luminal subtypes in the HER2-zero category (95%) and non-luminal (HER2-enriched and normal-like subtypes) in the HER2-low category (21%). Conclusions: In our sample, HER2-low category had a shorter median PFS in first line treatment with CDK4/6 inhibitors plus endocrine treatment compared to HER2-zero group. This finding was consistent for the three CDK4/6 inhibitors analyzed, although the HER2-low group showed more relative benefit in terms of PFS with palbociclib. Our results suggest a lower benefit of CDK4/6 inhibitors in the first line treatment of HER2-low MBC, which could be partially explained by a relative higher proportion of non-luminal PAM-50 subtypes in HER2-low tumors. FundingThis project has received a research grant from “Instituto de Salud Carlos III (ISCIII), Ministerio de Economía y Competitividad” (Spain) awarded within the National Research Program with reference PI 18/01408, co-funded with European Union ERDF funds (European Regional Development Fund).

Citation Format: Rodrigo Sanchez-Bayona, Santiago Terán, Ana Sánchez De Torre, Manuel Alva, Laura Lema, Luis Manso, Estefanía Toledo, Ana Maria Roncero, Cristina Merino, Mario Martínez, Lucía Parrilla, Eva Ciruelos, Pablo Tolosa. Efficacy of first line CDK4/6 inhibitors in HER2-low vs HER2-zero, hormone receptor positive, HER2 negative metastatic breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-13-24.

Abstract OT2-15-01: Updated analysis of MCLA-128 (zenocutuzumab), trastuzumab, and vinorelbine in patients (pts) with HER2 positive/amplified (HER2+) metastatic breast cancer (MBC) who progressed on previous anti-HER2 ADCs

Background Zenocutuzumab is a humanized bispecific full-length IgG1 antibody targeting both HER2 and HER3 with enhanced ADCC activity. The unique Dock & Block mechanism inhibits HER3 from interacting with its ligands by targeting HER2 at a different epitope than trastuzumab, that optimally positions it to block HER2/HER3 dimerization and downstream PI3K/AKT/mTOR signaling. In MBC, HER3 overexpression and/or HER3 ligand upregulation are important drivers of carcinogenesis leading to trastuzumab resistance, indicating a potential role for zenocutuzumab. Preclinical activity was seen in HER2+ breast cancer models when zenocutuzumab was combined with trastuzumab. Single-agent zenocutuzumab showed consistent antitumor activity in heavily pretreated HER2+ MBC pts. This phase 2, open-label study explored zenocutuzumab/trastuzumab/vinorelbine in MBC. Methods This open-label study planned to enroll up to 40 evaluable pts with HER2+ MBC progressing after up to 5 anti-HER2 lines of therapy including trastuzumab, pertuzumab, and an anti-HER2 ADC. This sample size with a clinical benefit rate (CBR) of 45% would provide adequate precision to exclude 30% (lower limit of 90% CI &gt; 30%). The threshold for the CBR rate at 24 w was based on the assumption that progression-free survival (PFS) follows an exponential distribution with a median of 5 months (clinically relevant) and 3.5 months (not clinically relevant).Pts received zenocutuzumab (750 mg, 2h IV), trastuzumab (8 mg/kg loading, then 6 mg/kg), and vinorelbine (25 mg/m², D1 and 8), q3w. A safety run-in of zenocutuzumab + trastuzumab ± vinorelbine was performed. The primary endpoint of the study was CBR at 24 w (tumor assessment [TA] by RECIST 1.1, per investigator), secondary endpoints include CBR at 24 w (TA by RECIST 1.1, per central review), overall response rate (ORR), safety, biomarkers, and pharmacokinetics. Cutoff date for the efficacy endpoints was 31Mar2021. This is an updated analysis of the 2020 ASCO abstract after all patients had completed at least 6 months of treatment or discontinued. Result total of 39 pts with a median of 3 lines (range 2-5) of prior anti-HER2 therapy including TDM1 received a median of 6 (range 1-23) cycles of zenocutuzumab. In the 37 pts evaluable for efficacy and with locally confirmed HER2 overexpression (3+ IHC or 2+ IHC confirmed by FISH), CBR at 24 w per investigator was 49% (90% CI: 34-63%); ORR was 27% (95% CI: 15-42%). The CBR at 24 w was consistent across different methods of HER2 overexpression/amplification detection (local vs central laboratory) and response assessment (investigator and central independent radiological review; see table below). As of a 12Jan2021 safety data update, the most common related AEs (all grades; G3-4) were neutropenia/neutrophil count decrease (61%; 46%), diarrhea (61%; 4%), asthenia/fatigue (46%; 0), and nausea (29%; 0). The PK half-life was 117h. The correlation of HER2-HER3 pathway activation at baseline with best ORR, duration of response, PFS, and overall survival was analyzed and will be presented in the poster. Conclusion Updated analyses confirm that the efficacy of zenocutuzumab combinations with trastuzumab/vinorelbine in heavily pretreated, HER2+ MBC, with progression after TDM-1, met prespecified protocol criteria for success. The regimen is safe and well tolerated with AEs mostly related to chemotherapy.

CBR with zenocutuzumab, trastuzumab, and vinorelbinePopulationNCBR at 24 wks, %. (90% CI)HER2+ by local test/TA by RECIST1.1 per investigator3749 (34-63)HER2+ by central test/TA by RECIST1.1 per investigator2955.1 (38-71)HER2+ by local test/TA by RECIST1.1 by central independent radiologist review3644 (30-59)HER2+ by central test/TA by RECIST1.1 by central independent radiologist review2850.0 (33-67)

Citation Format: Erika Hamilton, Thierry Petit, Barbara Pistilli, Anthony Goncalves, Ana Alexandra Ferreira, Florence Dalenc, Fatima Cardoso, Monica M Mita, Luis Manso, Syed M Karim, Francois-Clement Bidard, Philippe Aftimos, Santiago Escriváa-de-Romaníi, Noemia Afonso, Ernesto Wasserman, Kees Bol, Viktoriya Stalbovskaya, Anastasia Vliet, Anastasia Murat, Mohamed Bekradda, Thomas Bachelot. Updated analysis of MCLA-128 (zenocutuzumab), trastuzumab, and vinorelbine in patients (pts) with HER2 positive/amplified (HER2+) metastatic breast cancer (MBC) who progressed on previous anti-HER2 ADCs [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr OT2-15-01.

Abstract OT2-20-01: Rogaratinib, palbociclib and fulvestrant in advanced hormone receptor-positive (HR+), FGFR1/2-positive breast cancer: Phase I trial plus an expansion cohort

Background: Novel therapies are needed upon progression to first-line CDK4/6 inhibitor (CDKi) plus endocrine therapy in advanced HR+ breast cancer. One frequent alteration driving resistance to CDKi plus hormones is FGFR1/2 amplification/overexpression. We have demonstrated that a combined assay of RNAScope and FISH, detecting RNA overexpression and genomic amplification of FGFR1/2, captures more FGFR-aberrant cases than either test alone. When these alterations exist, the triple estrogen receptor (ER), CDK4/6 and FGFR1/2 blockade is able to revert acquired resistance to CDKi (Breast Cancer Res; 23:21-37; 2021). Rogaratinib is a selective FGFR1-4 kinase inhibitor with significant activity in FGFR-aberrant malignancies. In this trial we will test the safety of the triple blockade combining fulvestrant, palbociclib and rogaratinib. We will also study its role as a resistant-reversion combo for FGFR1/2-positive, HR+ patients progressing to a CDK4/6 inhibitor plus aromatase inhibitor (AI) in the first-line metastatic setting. Trial design: Single-arm, prospective, multicentric, open-label, phase I dose-escalation trial. Patients will be pre-screened for amplification and/or overexpression of FGFR1/2 by FISH and RNAScope, during their first-line treatment. Positive patients will start treatment: on day 1, patients will receive rogaratinib q12 hours. On day 2, patients will continue on rogaratinib, receive fulvestrant (500 ug IM) and start on palbociclib (100 mg/day on days 1-21). A second fulvestrant dose (500 ug) will be administered in day +15. The first cycle will be 29 days, followed by 28-day cycles (continuous rogaratinib q12 hours days 1-28, fulvestrant 500 ug day 1, and palbociclib 100 mg/day days 1-21). Rogaratinib will be escalated, starting on 400 mg/bid in 200 mg/bid increments, following a classic 3+3 schedule. Patients experiencing ≤ grade 1 tolerable side effects as the greatest toxicity will be allowed to escalate palbociclib to 125 in cycle 2. A full pharmacokinetic profile and pharmacodynamics (plasma FGF23 and phosphate levels) will be performed on days 1 and 15 of cycle 1. The impact of the triple combination in immunodynamics will be assessed on PBMCs on days 2 and 15. Ten additional HR+, FGFR1/2 + patients will be accrued at the RP2D in an expansion cohort to study efficacy. RECIST 1.1 and NCI CTC AE V 5.0 criteria will be used for assessing disease control (q8 weeks) and toxicity. Eligibility criteria: Pre-screening: Women &gt;18 year old diagnosed with advanced, non-curable HR+ breast cancer; 2) who are receiving first-line treatment with an AI and any oral CDKi; 3) Adequate organ function. Full screening: 4) Positivity for amplification (FISH ratio&gt;2.2) and/or overexpression (RNAScope score of 3+ or 4+) of either FGFR1/2. 5) PD to first-line AI + CDKi within the last 28 days. 6) Recovery from previous toxicity to &lt; tolerable G2. Specific aims: Primary: 1) To determine RP2D of the triple combination of fulvestrant, palbociclib and rogaratinib. 2) To assess the safety and toxicity of the former combination 3) To study the pharmacokinetics, pharmacodynamics and immunodynamics of the triplet. Secondary: 1) To determine the PFS time and 6-month PFS rate of the triplet in FGFR1/2 amplified/overexpressed patients AI + CDKi doublet. Statistical methods: We will follow a 3+3 escalation schedule; thus, the minimum and maximum number of patients for the dose-escalation phase will range between 6 and 18 (no escalation planned beyond 800 mg/bid rogaratinib). Ten additional patients will be accrued in the expansion cohort (N=28). The anticipated rate of positive screening is 40%; thus, we will screen approximately 70 patients. . Present accrual/target accrual: 55/70 screened; 16 FGFR1/2-positive (of 28 planned); 2 accrued and treated.

Citation Format: Sonia Pernas, Cristina Hernando, Begoña Bermejo, Noelia Martinez-Jañez, Jose A García Saenz, Serafin Morales, Luis Manso, Jorge Silva, Juan A Guerra, Diego Malon, Silvana Mouron, Eduardo Caleiras, Miguel Quintela-Fandino. Rogaratinib, palbociclib and fulvestrant in advanced hormone receptor-positive (HR+), FGFR1/2-positive breast cancer: Phase I trial plus an expansion cohort [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr OT2-20-01.

Abstract OT2-19-08: Phase IB/II trial of palbociclib and binimetinib in advanced triple-negative breast cancer with hyperactivation of ERK and/or CDK4/6

Background: Novel effective and safe therapies are required for advanced TNBC after progression to standard-of-care first line treatment with anti-PD-1/L1 + chemotherapy. We have found that the most aggressive TNBC variants are driven by a heterogeneous set of genetic aberrations that converge in the increased activity of 6 kinases: KIT, PNKP, PRKCE, P70S6K, ERK and CDK6 (Nat Commun; 9:3501-18). Although the inhibition of each kinase in monotherapy yielded little efficacy in preclinical models, the combinations targeting pairs of the former kinases led to therapeutic synergy in most cases. The combined inhibition of CDK6 and ERK led to 5-fold increase in overall survival in preclinical TNBC models (PDXs and spontaneous murine cancer models). The greatest activity was observed in models with increased activity of either CDK6 or ERK. Thus, we aimed to test the safety and preliminary efficacy of combined ERK and CDK6 inhibition with binimetinib and palbociclib in women with advanced TNBC with hyperactivation of ERK and/or CDK6. The combination has been preliminary tested in lung cancer, where a phase I dose-escalation trial established the RP2D in binimetinib 45 mg/BID plus Palbociclib 125 mg daily 21/7. Trial design: Single-arm, prospective, multicentric, open-label, phase IB/II trial with intra-patient dose-escalation. Patients candidate for pre-screening will have determined the activity of ERK and CDK6 with an in-house developed assay and acquisition algorithm at the central lab. Those testing positive for either marker will undergo full screening. Patients will start treatment with continuous oral binimetinib at 45 mg/BID and palbociclib 100 mg/day from days 1 to 21, in 28-day cycles. Patients experiencing ≤ grade 1 tolerable side effects as the greatest toxicity will be allowed to escalate to palbociclib to 125 in cycle 2. Fresh biopsies will be harvested at baseline and disease progression, in order to establish patient-derived organoids (PDOs) and perform WES. PBMCs will be harvested at baseline, +24 hours, and at the beginning of cycle 2, to study changes in the immunophenotype. RECIST 1.1 and NCI CTC AE V 5.0 criteria will be used for assessing disease control (q8 weeks) and toxicity. Eligibility criteria: Pre-screening: Women &gt;18 year old diagnosed of advanced, non-curable TNBC; 2) who have received a minimum of 1 treatment line including immunotherapy; 3) no more than 2 treatment lines for advanced disease; 4) Adequate organ function and recovery from previous toxicity to &lt; tolerable G2. Full screening: 5) Demonstration of hyper-activation of CDK6 and/or ERK in the tumor sample; 6) PD to the previous treatment regimen within the last 28 days. Specific aims: Primary: 1) To determine the progression-free survival time of the combination of binimetinib and palbociclib in TNBC patients with hyperactivation of ERK and/or CDK6 in second/third line 2) To assess the safety and tolerability of the former combination Secondary: 1) 6-month PFS rate, response rate, and overall survival of the combination 2) To study biomarkers of sensitivity and primary and acquired resistance to the combination taking advantage of PDOs 3) To determine the immunodynamics of the combination. Statistical methods: The null hypothesis is that the median PFS time for second/third line TNBC with best physician’s choice is 1.7 months (NEJM; 384:1529-41, 2021). With alpha and beta errors of 0.05 and 0.2, the minimum number of patients to demonstrate a 30% improvement in PFS to 2.5 months is 25. Preliminary data suggest that approximately 40% of the patients show hyper-activation of CDK6 and/or ERK; thus, and assuming a methodological failure of 10%, the minimum number of patients to screen is 69. Present accrual/target accrual: 27 screened of 69 planed; 11 accrued of 25 planned

Citation Format: Luis Manso, Alfonso Cortes, Juan M Cejalvo, Serafin Morales, Jose A García Saenz, Ramon Colomer, Rodrigo Sanchez-Bayona, Jorge Silva, Juan A Guerra, Diego Malon, Silvana Mouron, Eduardo Caleiras, Miguel Quintela-Fandino. Phase IB/II trial of palbociclib and binimetinib in advanced triple-negative breast cancer with hyperactivation of ERK and/or CDK4/6 [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr OT2-19-08.

Genomic landscape and immune-related gene expression profiling of epithelial ovarian cancer after neoadjuvant chemotherapy

Platinum-based neoadjuvant chemotherapy followed by interval debulking surgery is an accepted treatment for patients with stage III or IV epithelial ovarian cancer who are not suitable for primary debulking surgery. The identification of suitable adjuvant treatments in these patients is an unmet need. Here, we explore potential genomic characteristics (mutational and immune-associated expression profiles) in a series of patients undergoing neoadjuvant chemotherapy. Tumor samples from biopsy and interval debulking surgery were analyzed for mutational landscape and immune profiling, together with detailed immunohistochemistry using different immune cell markers, and correlated with clinicopathological characteristics and potential response to neoadjuvant chemotherapy. No major differences in the mutational landscape were observed in paired biopsy and surgery samples. Genomic loss of heterozygosity was found to be higher in patients with total/near-total tumor response. The immune gene expression profile after neoadjuvant chemotherapy revealed activation of several immune regulation-related pathways in patients with no/minimal or partial response. In parallel, neoadjuvant therapy caused a significant increase of tumor-infiltrating lymphocyte population abundance, primarily due to an augmentation of the CD8+ T cell population. Remarkably, these changes occurred irrespective of potential homologous recombination defects, such as those associated with BRCA1/2 mutations. Our study strengthens the use of loss of heterozygosity as a biomarker of homologous repair deficiency. The changes of immune states during neoadjuvant chemotherapy reveal the dynamic nature of tumor-host immune interactions and suggest the potential use of immune checkpoint inhibitors or their combination with poly-ADP polymerase inhibitors in high stage and grade epithelial ovarian cancer patients undergoing neoadjuvant therapy.

531 A Phase 1b multi-tumor cohort study of cabozantinib plus atezolizumab in advanced solid tumors: results of the triple-negative breast cancer, ovarian cancer, and endometrial cancer cohorts

Background

Cabozantinib, a multiple receptor tyrosine kinase inhibitor, promotes an immune-permissive environment which might enhance the activity of immune checkpoint inhibitors. COSMIC-021 (NCT03170960), a multicenter phase 1b study, is evaluating the combination of cabozantinib with atezolizumab in advanced solid tumors; here we present efficacy and safety results in patients with triple negative breast cancer (TNBC), ovarian cancer (OC), and endometrial cancer (EC).

Methods

Eligible patients had locally advanced or metastatic TNBC, OC, or EC and had radiographically progressed on prior systemic anticancer therapy. One or two lines of prior therapy were permitted. Patients with OC were platinum resistant or refractory. Prior treatment with anti-PD-1 or anti-PD-L1 agents was allowed for patients with TNBC. Patients received cabozantinib, 40 mg PO QD, plus atezolizumab, 1200 mg IV Q3W. The primary endpoint was objective response rate (ORR) per RECIST 1.1 as assessed by investigator. Other endpoints included safety, duration of response (DOR), progression free survival (PFS), and overall survival (OS). CT/MRI scans were performed Q6W for the first year and Q12W thereafter.

Results

As of February 19, 2021, 30–32 patients were enrolled in each of the cohorts. 47% of patients with TNBC, 47% with OC, and 40% with EC had received 2 lines of prior therapy. Median follow-up was 18.7 months, 20.8 months, and 19.0 months for the TNBC, OC, and EC cohorts, respectively. Grade 3/4 treatment-related adverse events occurred in 33% of patients with TNBC, 56% with OC, and 37% with EC. One Grade 5 treatment-related adverse event of pulmonary hemorrhage occurred in the TNBC cohort and one of encephalitis occurred in the OC cohort. Cabozantinib plus atezolizumab demonstrated clinical activity in all three tumor cohorts (table 1).

Abstract 531 Table 1

Conclusions

Cabozantinib in combination with atezolizumab demonstrated encouraging clinical activity in patients with previously treated advanced cancers.

Acknowledgements

Medical writing support provided by Suvajit Sen, PhD (Exelixis, Inc.)

Trial Registration

NCT03170960

Ethics Approval

Yes

Consent

Yes

Niraparib for Advanced Breast Cancer with Germline BRCA1 and BRCA2 Mutations: the EORTC 1307-BCG/BIG5-13/TESARO PR-30-50-10-C BRAVO Study

PURPOSE

To investigate the activity of niraparib in patients with germline-mutated BRCA1/2 (gBRCAm) advanced breast cancer.

PATIENTS AND METHODS

BRAVO was a randomized, open-label phase III trial. Eligible patients had gBRCAm and HER2-negative advanced breast cancer previously treated with ≤2 prior lines of chemotherapy for advanced breast cancer or had relapsed within 12 months of adjuvant chemotherapy, and were randomized 2:1 between niraparib and physician's choice chemotherapy (PC; monotherapy with eribulin, capecitabine, vinorelbine, or gemcitabine). Patients with hormone receptor-positive tumors had to have received ≥1 line of endocrine therapy and progressed during this treatment in the metastatic setting or relapsed within 1 year of (neo)adjuvant treatment. The primary endpoint was centrally assessed progression-free survival (PFS). Secondary endpoints included overall survival (OS), PFS by local assessment (local-PFS), objective response rate (ORR), and safety.

RESULTS

After the pre-planned interim analysis, recruitment was halted on the basis of futility, noting a high degree of discordance between local and central PFS assessment in the PC arm that resulted in informative censoring. At the final analysis (median follow-up, 19.9 months), median centrally assessed PFS was 4.1 months in the niraparib arm (n = 141) versus 3.1 months in the PC arm [n = 74; hazard ratio (HR), 0.96; 95% confidence interval (CI), 0.65-1.44; P = 0.86]. HRs for OS and local-PFS were 0.95 (95% CI, 0.63-1.42) and 0.65 (95% CI, 0.46-0.93), respectively. ORR was 35% (95% CI, 26-45) with niraparib and 31% (95% CI, 19-46) in the PC arm.

CONCLUSIONS

Informative censoring in the control arm prevented accurate assessment of the trial hypothesis, although there was clear evidence of niraparib's activity in this patient population.

Abstract CT191: A window-of-opportunity study with atezolizumab and the oncolytic virus pelareorep in early breast cancer (AWARE-1)

Background: A previous phase 2 study in metastatic breast cancer demonstrated a statistically significant improvement in overall survival (OS) in patients treated with pelareorep (pela), an intravenously delivered immuno-oncolytic reovirus, given in combination with paclitaxel (PTX) versus PTX alone [1]. We hypothesized that the OS benefit from pela + PTX may be attributed to an adaptive T cell response triggered by pela. To examine if pela can mediate the priming of an anti-tumor immune response, and the impact of checkpoint blockade therapy on this response, we and SOLTI research group are conducting the AWARE-1 study (NCT04102618) in patients with early breast cancer. The initial translational research results from this study are presented here. Methods: AWARE-1 is a window-of-opportunity study to evaluate the safety and effect of pela ± atezolizumab on the tumor microenvironment (TME) in 38 women with early breast cancer. Patients are treated with pela on days 1, 2, 8, and 9, and atezolizumab is administered on day 3. Tumor biopsies are collected at diagnosis, day 3, and day ~21. Five patient cohorts are being examined: Cohort 1: HR+/HER2-neg (10 patients) receiving pelareorep + letrozole (without atezolizumab); Cohort 2: HR+/HER2-neg (10 patients) receiving pelareorep + letrozole + atezolizumab; Cohort 3: TNBC (6 patients) receiving pelareorep + atezolizumab; Cohort 4: HR+/HER2+ (6 patients) receiving pelareorep + trastuzumab + atezolizumab; Cohort 5: HR-neg/HER+ (6 patients) receiving pelareorep + trastuzumab + atezolizumab. The primary endpoint is CelTIL score [2], a metric for quantifying changes in tumor cellularity and the number of tumor infiltrating lymphocytes (TILs), where an increase in CelTIL score has been associated with a favorable response to treatment. Tumor tissue is being examined for pela replication, changes to the TME by immunohistochemistry (IHC), PD-L1 expression by the Ventana SP142 assay used as the atezolizumab companion diagnostic, and T cell clonality by T cell receptor sequencing (TCR-seq). Peripheral blood is also being examined by TCR-seq. Results: Changes in the TME by IHC demonstrate that treatment with pela in the presence of atezolizumab increases the CD8/Treg ratio, a predictor of greater therapeutic efficacy, similar to preclinical breast cancer mouse models [3, 4]. Detailed TCR-seq, Ventana PD-L1 assay results, and IHC analysis will be presented, focusing on differences between patients receiving pela in the absence or presence of atezolizumab (Cohorts 1 and 2, respectively), and between CelTIL scores of responders and non-responders. Overall, these data demonstrate that pela can promote an inflamed tumor phenotype that allows for synergy with checkpoint blockade therapy in breast cancer.

References: [1] Bernstein, V., et al. Breast Cancer Res Treat, 2018. 167(2): p. 485-493. [2] Nuciforo, P., et al. Ann Oncol, 2018. 29(1): p. 170-177. [3] Mostafa, A.A., et al. Cancers (Basel), 2018. 10(6). [4] Lee, J., et al. Cancer Research, 2020. 80(16 Supplement): p. 2206-2206.

Citation Format: Luis Manso, Fernando Salvador, Patricia Villagrasa, Nuria Chic, Begoña Bermejo, Juan M. Cejalvo, Yann Izarzugaza, Blanca Cantos, Salvador Blanch, Mireia Margeli, Jose L. Alonso, Alejandro Martínez, Rafael Villanueva, Juan A. Guerra, Raquel Andrés, Pilar Zamora, Esteban Nogales, Manel Juan, Blanca Gonzalez-Farre, Grey A. Wilkinson, Thomas C. Heineman, Gerard Nuovo, Houra Loghmani, Matt Coffey, Azucena Gonzalez, Débora Martínez, Laia Paré, Tomás Pascual, Xavier Gonzalez, Aleix Prat, Joaquín Gavilá. A window-of-opportunity study with atezolizumab and the oncolytic virus pelareorep in early breast cancer (AWARE-1) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT191.

Management of advanced ovarian cancer in Spain: an expert Delphi consensus

BACKGROUND

To determine the state of current practice and to reach a consensus on recommendations for the management of advanced ovarian cancer using a Delphi survey with a group of Spanish gynecologists and medical oncologists specially dedicated to gynecological tumors.

METHODS

The questionnaire was developed by the byline authors. All questions but one were answered using a 9-item Likert-like scale with three types of answers: frequency, relevance and agreement. We performed two rounds between December 2018 and July 2019. A consensus was considered reached when at least 75% of the answers were located within three consecutive points of the Likert scale.

RESULTS

In the first round, 32 oncologists and gynecologists were invited to participate, and 31 (96.9%) completed the online questionnaire. In the second round, 27 (87.1%) completed the online questionnaire. The results for the questions on first-line management of advanced disease, treatment of patients with recurrent disease for whom platinum might be the best option, and treatment of patients with recurrent disease for whom platinum might not be the best option are presented.

CONCLUSIONS

This survey shows a snapshot of current recommendations by this selected group of physicians. Although the majority of the agreements and recommendations are aligned with the recently published ESMO-ESGO consensus, there are some discrepancies that can be explained by differences in the interpretation of certain clinical trials, reimbursement or accessibility issues.

Efficacy and safety of weekly paclitaxel in elderly patients with heavily pretreated platinum-resistant ovarian carcinoma

e17552

Background: In platinum-resistant ovarian cancer treatment, single-agent paclitaxel can be used alone or in combination with bevacizumab. We aimed to assess the efficacy and safety profile of a weekly paclitaxel (WP) scheme in heavily pretreated platinum-resistant high-grade serous ovarian carcinoma. Methods: We retrospectively analyzed 30 adult patients with platinum-resistant high-grade serous ovarian carcinoma treated with WP at our institution between 2015 and 2020. Patients with platinum-resistant ovarian, fallopian tube or primary carcinoma of the peritoneum who had received at least 3 doses of WP (80 mg/m2) alone or in combination with bevacizumab until disease progression or unacceptable toxicity were included in the analysis. Progression-free survival was assessed according to the Response Evaluation Criteria in Solid Tumors version 1.1. Information about toxicity was gathered from medical reports and lab tests. Kaplan-Meier curves and Log-rank test were performed for survival estimates. Results: In our sample, the median age was 68 years (IQR: 60-75) and the median number of previous lines of systemic treatment was 3 (range 1-5). 40% of patients received WP in combination with bevacizumab. The disease control rate was 60.7% (42.9% partial response and 17.8% stable disease). In the overall analysis, the median progression-free survival (mPFS) was 5.0 months (95% CI: 2.0-7.1 months). The presence of ascites significantly shortened the mPFS compared to patients without it (1.1 vs 5.1 months, p < 0.001). Even though the addition of bevacizumab to WP improved the mPFS, the difference was not statistically significant compared to WP alone (7.1 vs 4.06 months, p=0.30). Peripheral neuropathy was the most common adverse event (78% all grades, 18% grade 3). No grade 3 hematologic toxicity was registered. Treatment was discontinued in 6 patients (20%) – 4 due to peripheral neuropathy and two because of toxicoderma. Conclusions: In our sample, WP was an active and safe regimen in heavily pretreated platinum-resistant ovarian carcinoma. WP was well tolerated in elderly patients. The presence of ascites was associated to a shorter PFS in patients treated with WP compared to ascites-free patients.

Serial Analysis of Circulating Tumor Cells in Metastatic Breast Cancer Receiving First-Line Chemotherapy

BACKGROUND

We examined the prognostic significance of circulating tumor cell (CTC) dynamics during treatment in metastatic breast cancer (MBC) patients receiving first-line chemotherapy.

METHODS

Serial CTC data from 469 patients (2202 samples) were used to build a novel latent mixture model to identify groups with similar CTC trajectory (tCTC) patterns during the course of treatment. Cox regression was used to estimate hazard ratios for progression-free survival (PFS) and overall survival (OS) in groups based on baseline CTCs, combined CTC status at baseline to the end of cycle 1, and tCTC. Akaike information criterion was used to select the model that best predicted PFS and OS.

RESULTS

Latent mixture modeling revealed 4 distinct tCTC patterns: undetectable CTCs (56.9% ), low (23.7%), intermediate (14.5%), or high (4.9%). Patients with low, intermediate, and high tCTC patterns had statistically significant inferior PFS and OS compared with those with undetectable CTCs (P < .001). Akaike Information Criterion indicated that the tCTC model best predicted PFS and OS compared with baseline CTCs and combined CTC status at baseline to the end of cycle 1 models. Validation studies in an independent cohort of 1856 MBC patients confirmed these findings. Further validation using only a single pretreatment CTC measurement confirmed prognostic performance of the tCTC model.

CONCLUSIONS

We identified 4 novel prognostic groups in MBC based on similarities in tCTC patterns during chemotherapy. Prognostic groups included patients with very poor outcome (intermediate + high CTCs, 19.4%) who could benefit from more effective treatment. Our novel prognostic classification approach may be used for fine-tuning of CTC-based risk stratification strategies to guide future prospective clinical trials in MBC.

Safety and efficacy of abemaciclib plus endocrine therapy in older patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative advanced breast cancer: an age-specific subgroup analysis of MONARCH 2 and 3 trials

PURPOSE

Abemaciclib in combination with endocrine therapy (ET) has demonstrated significant efficacy benefits in HR+ , HER2- advanced breast cancer patients in the Phase 3 studies MONARCH 2 (fulvestrant as ET) and MONARCH 3 (letrozole or anastrozole as ET). Here, we report age-specific safety and efficacy outcomes.

METHODS

Exploratory analyses of MONARCH 2 and 3 were performed for 3 age groups (<65, 65-74, and ≥75 years). For safety, data were pooled from both studies; for efficacy, a subgroup analysis of PFS was performed for each trial independently.

RESULTS

Pooled safety data were available for 1152 patients. Clinically relevant diarrhea (Grade 2/3) was higher in older patients receiving abemaciclib + ET (<65, 39.5%; 65-74, 45.2%; ≥75, 55.4%) versus placebo + ET (<65, 6.8%; 65-74, 4.5%; ≥75, 16.0%). Nausea, decreased appetite, and venous thromboembolic events were all moderately higher in older patients. Neutropenia (Grade ≥ 3) did not differ as a function of age in the abemaciclib + ET arm (<65, 25.8%; 65-74, 27.4%; ≥75, 18.1%). Dose adjustments and discontinuation rates were slightly higher in older patients. Abemaciclib + ET improved PFS compared with placebo + ET independent of patient age, with no significant difference in abemaciclib treatment effect between the 3 age groups (MONARCH 2: interaction p-value, 0.695; MONARCH 3: interaction p-value, 0.634). Estimated hazard ratios ranged from 0.523-0.633 (MONARCH 2) and 0.480-0.635 (MONARCH 3).

CONCLUSIONS

While higher rates of adverse events were reported in older patients, they were manageable with dose adjustments and concomitant medication. Importantly, a consistent efficacy benefit was observed across all age groups.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov: NCT02107703 (first posted April 8, 2014) and NCT02246621 (first posted September 23, 2014).

Immune microenvironment characterisation and dynamics during anti-HER2-based neoadjuvant treatment in HER2-positive breast cancer

Despite their recognised role in HER2-positive (HER2+) breast cancer (BC), the composition, localisation and functional orientation of immune cells within tumour microenvironment, as well as its dynamics during anti-HER2 treatment, is largely unknown. We here investigate changes in tumour-immune contexture, as assessed by stromal tumour-infiltrating lymphocytes (sTILs) and by multiplexed spatial cellular phenotyping, during treatment with lapatinib-trastuzumab in HER2+ BC patients (PAMELA trial). Moreover, we evaluate the relationship of tumour-immune contexture with hormone receptor status, intrinsic subtype and immune-related gene expression. sTIL levels increase after 2 weeks of HER2 blockade in HR-negative disease and HER2-enriched subtype. This is linked to a concomitant increase in cell density of all four immune subpopulations (CD3+, CD4+, CD8+, Foxp3+). Moreover, immune contexture analysis showed that immune cells spatially interacting with tumour cells have the strongest association with response to anti-HER2 treatment. Subsequently, sTILs consistently decrease at the surgery in patients achieving pathologic complete response, whereas most residual tumours at surgery remain inflamed, possibly reflecting a progressive loss of function of T cells. Understanding the features of the resulting tumour immunosuppressive microenvironment has crucial implications for the design of new strategies to de-escalate or escalate systemic therapy in early-stage HER2+ BC.

Abstract PS12-08: A window-of-opportunity study with atezolizumab and the oncolytic virus pelareorep in early breast cancer (REO-027, AWARE-1)

Background: A previous phase 2 study in metastatic breast cancer compared treatment with intravenously delivered oncolytic reovirus, pelareorep (pela), in combination with paclitaxel (PTX) versus PTX alone. This study demonstrated a statistically significant improvement in overall survival (OS), without differences in objective response or progression-free survival. We hypothesized that the OS benefit from pela + PTX may be attributed to an adaptive immune response triggered by pela. To test this hypothesis, and examine if pela can mediate the priming of an anti-tumor immune response, we designed a study called AWARE-1 (A window-of-opportunity study of pela in Early Breast Cancer), which is currently enrolling and for which initial translational research results are presented.

Methods: AWARE-1 is evaluating the safety and effect of pela ± atezolizumab on the tumor microenvironment (TME) in 38 women with early breast cancer. Patients are treated with pela on days 1, 2, 8, and 9, while atezolizumab is administered on day 3. Tumor biopsies are collected at diagnosis, day 3, and day ~21. Five cohorts will be examined: Cohort 1: Hormone Receptor-positive/HER2-negative (HR+/HER2-neg) (10 patients), pelareorep + letrozole. Cohort 2: HR+/HER2-neg (10 patients), pelareorep + letrozole + atezolizumab. Cohort 3: Triple Negative Breast Cancer (TNBC) (6 patients), pelareorep + atezolizumab. Cohort 4: Hormone Receptor-positive/HER2-positive (HR+/HER2+) (6 patients), pelareorep + trastuzumab + atezolizumab. Cohort 5: Hormone Receptor-negative/HER2-positive (HR-/HER2+) (6 patients), pelareorep + trastuzumab + atezolizumab. The primary endpoint of the study is CelTIL score, a metric for quantifying the changes in tumor cellularity and infiltration of TILs, where an increase in CelTIL is associated with a favorable response to treatment. Tumor tissue was examined for pela replication, and changes to the TME were assessed by imaging mass cytometry (IMC), immunohistochemistry, and T cell receptor sequencing (TCR-seq). Peripheral blood was also examined by TCR-seq.

Results: Detailed translational research results will be presented from patients in cohort 1, who received just pelareorep and letrozole. CelTIL score increased in 5/10 patients at day 3 biopsies and 6/10 patients at day 21 biopsies. Preliminary results show high levels of viral replication (&gt;50% of tumor cells) while immunohistochemistry and IMC analysis revealed changes to the TME, with increases in CD8+ T cells and upregulation of PD-L1 at both day 3 and day 21 biopsies. Overall, preliminary data from cohort 1 of AWARE-1 demonstrate pela-mediated priming of an adaptive immune response. (NCT04102618)

Citation Format: Luis Manso, Patricia Villagrasa, Nuria Chic, Begoña Bermejo, Juan Miguel Cejalvo, Yann Izarzugaza, Blanca Cantos, Salvador Blanch, Mireia Margeli, Jose Luis Alonso, Alejandro Martínez, Rafael Villanueva, Juan Antonio Guerra, Raquel Andrés, Pilar Zamora, Esteban Nogales, Manel Juan, Blanca González, Rita Laeufle, Gerard Nuovo, Grey Wilkinson, Matt Coffey, Azucena González, Débora Martínez, Laia Paré, Fernando Salvador, Xavier Gonzalez, Aleix Prat, Joaquín Gavilá. A window-of-opportunity study with atezolizumab and the oncolytic virus pelareorep in early breast cancer (REO-027, AWARE-1) [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS12-08.

Abstract OT-09-08: Solti-1502 aRIANNA: Targeting PAM50 HER2-enriched intrinsic subtype with enzalutamide in hormone receptor-positive/HER2-negative metastatic breast cancer

Background Pre-clinical evidence and retrospective studies suggest that PAM50 HER2-Enriched (HER2-E), hormone receptor-positive (HR+)/HER2-negative tumors have estrogen receptor (ER)-independency and poor prognosis, but seem to have androgen receptor (AR)-addiction (1). Enzalutamide (EZM) is a potent inhibitor of androgen receptor signaling (3). AR expression has been shown to induce resistance to both tamoxifen and aromatase inhibitors in estrogen receptor HR-expressing cell lines (4,5) The hypothesis of the ARIANNA trial is that EZM induces a significant proliferative arrest in PAM50 HER2-E, HR+/HER2-negative advanced breast cancer (BC), leading to clinical benefit in this poor prognosis population. Methods ARIANNA is an exploratory, phase II clinical trial in two independent cohorts evaluating the effect of EZM on proliferation after 2 weeks (+7 days window) on treatment in pre- or post-menopausal female or male patients with endocrine-resistant, locally advanced or metastatic HR+/HER2-negative BC. Cohort A will include 22 patients with PAM50 HER2-E HR+/HER-negative tumors and Cohort B (control group) will include 22 patients with PAM50 Luminal A/B HR+/HER2-negative tumors. Fresh tumor biopsy will be obtained at screening and sent to central laboratory for PAM50 subtyping determination to confirm the molecular subtype status prior to study treatment initiation, and to determine PAM50 11-gene proliferation-related signature. Patients with PAM50 Basal-like or Normal-like tumors will be excluded. Patients will receive EZM 160 mg once a day (QD). After 2 weeks on treatment, a tumor biopsy from the same baseline lesion (or, if not feasible, a lesion in the same organ) will be obtained for the purpose of the primary endpoint analysis. After this on-treatment biopsy, exemestane 50mg QD can be added to EZM at physician’s discretion. Tumor assessment will be performed at screening and every 8 weeks thereafter. Treatment will be continued until disease progression, unacceptable toxicity, investigator’s decision or withdrawal of consent. An optional tumor biopsy will be collected at the end of treatment. The primary objective is to evaluate the anti-proliferative effect of EZM after 2 weeks of treatment in patients with HER2-E HR+/HER2-negative tumors, measured as relative changes in the PAM50 11-gene proliferation-related signature by the PAM50 nCounter-based assay between baseline and on-treatment tumor biopsies. Secondary objectives include: anti-proliferative effect of EZM after 2 weeks of treatment in patients included in Cohort B (control group), safety, overall response rate, progression-free survival, and further correlative molecular analyses both at the tumor tissue (IHC, RNA and DNA) and ctDNA level for both cohorts. The trial will enroll patients in 8 Spanish sites and recruitment period will be 18 months. Funding was granted by Breast Cancer Research Foundation and drug was supplied by Astellas Pharma Global Development, Inc./Pfizer, Inc. Trial identification: NCT04142060 1. Cochrane DR, Bernales S, Jacobsen BM, Cittelly DM, Howe EN, D’Amato NC, et al. Role of the androgen receptor in breast cancer and preclinical analysis of enzalutamide. Breast Cancer Res. 2014;16:R7. 3. Tran C, Ouk S, Clegg NJ, Chen Y, Watson PA, Arora V, et al. Development of a Second-Generation Antiandrogen for Treatment of Advanced Prostate Cancer. Science. 2009;324:787-90. 4. Rechoum Y, Rovito D, Iacopetta D, Barone I, Andò S, Weigel NL, et al. AR collaborates with ERα in aromatase inhibitor-resistant breast cancer. Breast Cancer Res Treat. 2014;147:473-85. 5. De Amicis F, Thirugnansampanthan J, Cui Y, Selever J, Beyer A, Parra I, et al. Androgen receptor overexpression induces tamoxifen resistance in human breast cancer cells. Breast Cancer Res Treat. 2010;121:1-11

Citation Format: Mafalda Oliveira, Sonia Pernas, Mireia Margelí, Salvador Blanch, Barbara Adamo, Javier Salvador Bofill, Diana Moreno, Xavier Gonzalez-Farré, José Rios, Charles M Perou, Aleix Prat, Tomás Pascual, Juan M Ferrero-Cafiero, Patricia Villagrasa, Luis Manso. Solti-1502 aRIANNA: Targeting PAM50 HER2-enriched intrinsic subtype with enzalutamide in hormone receptor-positive/HER2-negative metastatic breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr OT-09-08.

Abstract PS12-13: Balixafortide (a CXCR4 antagonist) plus eribulin in HER2 negative metastatic breast cancer: Final analysis from the Phase 1 single arm trial

Background: Balixafortide (B) is a potent, selective antagonist of the chemokine receptor CXCR4. High CXCR4 levels correlate with aggressive metastatic phenotypes and poor prognosis in metastatic breast cancer (MBC). Efficacy and safety data were published recently from the Phase 1 trial investigating B + eribulin (E) in patients with HER2 negative MBC1. We report the final safety and efficacy analyses from this trial, including an assessment of dose-response and adverse events of particular interest (AEPIs) (e.g. neutropenia, peripheral neuropathy).

Methods: In this single-arm, dose escalation trial, patients (pts) received E + increasing doses of B using a 3+3 design in 3 parts: Part I cohorts received low B doses (0.5−1mg/kg) + increasing E doses (1.1−1.4mg/m2); Part II dose-escalation cohort for B (1−5.5mg/kg) + 1.4mg/m2 E; Expanded Cohort (EC) to confirm safety and efficacy of B 5.5mg/kg + 1.4mg/m2 E. Most cohorts received E on days 2 and 9, and B on days 1−3 and 8−10 of 21-day cycles.

Results: At entry, all 56 women (age range 33−82 years) were HER2 negative, CXCR4 positive. Most pts were Caucasian and heavily pretreated in the metastatic setting (line of chemotherapy on study: 29% 2nd line, 50% 3rd line, 21% 4th line). 75% were hormone receptor positive and 23% had triple negative breast cancer.

A linear dose-exposure was observed over the entire dose range tested for B. Cmax and AUC for E were within published ranges.

Safety findings (including AEPIs) remained similar to those reported previously1.

No dose-limiting toxicities were confirmed; therefore, the maximum tolerated dose of B was not reached. The highest B dose evaluated was 5.5mg/kg; pharmacokinetic evaluation showed that further protocolled dose increments of B would not have provided a sufficient increase in plasma levels. In addition, the objective response rate in Part II was 3-fold greater than published for eribulin alone which suggested that the anti-tumor activity of B was worthy of further exploration at 5.5mg/kg in the EC.

Efficacy data for the trial are shown in the table.

These data suggest a potential dose-response relationship for B across all efficacy endpoints, with efficacy being numerically greatest in the EC. While PFS and OS should be interpreted with caution in single arm trials, these data suggest potential benefit for this combination. Further analyses will be presented.

Responses were observed regardless of line of chemotherapy on study or extent of CXCR4 expression and were numerically higher in hormone receptor positive patients.

Conclusions: A consistent dose response effect for B + E was suggested across all efficacy endpoints for heavily pretreated pts with HER2 negative MBC. When these results are compared with published data for E monotherapy in similar populations, the EC consistently shows numerically greater benefit for all efficacy endpoints2, 3.

The safety and tolerability of B + E appear comparable to published data on E or B alone, particularly for neutropenia and peripheral neuropathy1.

These results suggest that B + E could potentially provide a new treatment option in heavily pretreated patients with HER2 negative MBC. A Phase 3 trial exploring efficacy and safety of B 5.5mg/kg + E is ongoing.

1. Pernas S et al. Lancet Oncol. 2018; 19: 812−242. Cortes J et al. Lancet. 2011; 377: 914−9233. Kaufman PA et al. J Clin Oncol. 2015; 33: 594−601

Part II(N=21)Expanded Cohort(N=24)Overall Efficacy Population(N=54)Objective Response Rate (95% CI)33% (15−57)38% (19−59)30% (18−44)median duration in months (IQR)2.8 (1.4−3.3)4.4 (3.1−5.3)3.2 (2.2−4.5)Clinical Benefit Rate (95% CI)43% (22−66)63% (41−81)44% (31−59)median duration in months (IQR)5.4 (4.2−6.7)8.1 (6.3−10.8)6.9 (5.4−10.3)median PFS in months (95% CI)4.2 (3−5.4)6.2 (2.9−8.1)4.6 (3.2–5.7)median OS in months (95% CI)10.4 (7.7−18.4)18 (12.2–27.2)16.8 (10.6–18.4)Landmark OS estimate12 months (95% CI)40% (19−60)75% (53−88)60% (45−72)18 months (95% CI)30% (12−50)50% (29−68)42% (29−55)24 months (95% CI)20% (6−39)33% (16−52)25% (14−37)CI: confidence interval; IQR: interquartile range; OS: overall survival; PFS: progression free survival

Citation Format: Peter A. Kaufman, Sonia Pernas, Miguel Martin, Marta Gil-Martin, Patricia Gomez Pardo, Sara Lopez-Tarruella, Luis Manso, Eva Ciruelos, Jose Alejandro Perez-Fidalgo, Cristina Hernando, Foluso O Ademuyiwa, Katherine Weilbaecher, Ingrid A Mayer, Timothy J. Pluard, Maria Martinez Garcia, Francois Ringeisen, Daniela Schmitter, Javier Cortes. Balixafortide (a CXCR4 antagonist) plus eribulin in HER2 negative metastatic breast cancer: Final analysis from the Phase 1 single arm trial [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS12-13.

Abstract GS4-08: Clinical utility of repeated circulating tumor cell (CTC) enumeration as early treatment monitoring tool in metastatic breast cancer (MBC) - a global pooled analysis with individual patient data

Background:

Several studies suggest clinical utility of serial circulating tumor cell (CTC) enumeration as a means of assessing response status in metastatic breast cancer (MBC). The aim of this study is to conduct a comprehensive pooled analysis comprising globally available data to further define and explore the role of CTC enumeration as a tool for early treatment monitoring in patients with MBC with a focus on the predictive power in different breast cancer subtypes and clinical settings.

Methods:

In a global effort, peer-reviewed published studies with data on repeated CTC assessments (CellSearch® technology; Menarini Silicon Biosystems; Bologna, Italy) in MBC patients were screened and investigators were asked to provide individual patient data for this pooled analysis. 2761 cases from 32 data sets with data on both baseline and one follow up CTC assessments were included in the analysis (median time interval between the two CTC assessments 35 days). Data were analyzed using log rank tests and Cox regressions to evaluate the association between serial CTC enumeration results and overall survival (OS) in the full patient cohort and defined subgroups.

Results:

588 (21.3%) patients had no CTCs at both time points (neg/neg), 236 (8.5%) patients were CTC negative at baseline and CTC positive at follow up (neg/pos), 712 (25.8%) patients converted from CTC positive at baseline to CTC negative (pos/neg), and 1225 (44.4%) patients had at least one CTC at both time points (pos/pos). Log rank tests showed significant differences in OS between these four CTC change groups (p &lt; 0.0001 for all pairwise comparisons except for the comparison between neg/pos and pos/neg, p = 0.015). Median OS for the neg/neg, neg/pos, pos/neg and pos/pos group was 45.6, 26.1, 34.6, and 17.6 months, respectively. Hazard ratios (HR) (reference group neg/neg) were 1.38 (95% CI 1.16 - 1.64) for the pos/neg group, 1.78 (95% CI 1.43 - 2.22) for the neg/pos group, and 3.06 (95% CI 2.63 - 3.56) for the pos/pos group. Results were similar if a cutoff of 5 CTCs was used for CTC positivity (pos/neg group: HR 1.43, 95% CI 1.25 - 1.63; neg/pos group: HR 2.39, 95% CI 1.91 - 2.99; pos/pos group: HR 3.54, 95% CI 3.12 - 4.02).

In total, 2586 patients could be assigned to different tumor subtypes based on known hormone receptor (ER) and HER2 status of the primary tumor: 1513 (58.5%) patients had a luminal-like tumor (ER positive, HER2 negative), 682 (26.4%) patients had a HER2-positive tumor, and 391 (15.1%) patients had a triple-negative tumor. In patients with luminal-like tumors, the hazard ratios were 1.67 (95% CI 1.29 - 2.17), 2.01 (95% CI 1.45 - 2.77), and 3.87 (95% CI 3.09 - 4.83) for the pos/neg, neg/pos, and pos/pos group, respectively. In patients with HER2-positive tumors, the neg/pos group (HR 1.68, 95% CI 1.12 - 2.53) and the pos/pos group (HR 2.11, 95% CI 1.58 - 2.83) showed significantly worse OS compared to the neg/neg group, while in triple-negative patients, the pos/pos group had a significantly shorter OS compared to the neg/neg group (HR 2.99, 95% CI 2.11 - 4.24).

The results will be up-dated by inclusion of additional large data sets (CALGB 40502, CALGB 40503, COMET, SWOG S0500, TBCRC 001) for the analysis to be presented at SABCS 2020.

Conclusion:

This large pooled analysis confirms that at a median of 35 days after treatment initiation, follow-up CTC assessments strongly predict overall survival. These results suggest potential clinical utility of CTC monitoring as early response marker in MBC, especially in luminal-like tumors.

Citation Format: Wolfgang J Janni, Tracy C. Yab, Daniel F. Hayes, Massimo Cristofanilli, Francois-Clement Bidard, Michail Ignatiadis, Meredith M. Regan, Catherine Alix-Panabières, William E. Barlow, Carlos Caldas, Lisa A. Carey, Luc Dirix, Tanja Fehm, Jose A. Garcia-Saenz, Paola Gazzaniga, Daniele Generali, Lorenzo Gerratana, Rafael Gisbert-Criado, William Jacot, Zefei Jiang, Evi Lianidou, Mark J.M. Magbanua, Luis Manso, Dimitrios Mavroudis, Volkmar Müller, Elisabetta Munzone, Klaus Pantel, Jean-Yves Pierga, Brigitte Rack, Sabine Riethdorf, Hope S. Rugo, Kostandinos Sideras, Stefan Sleijfer, Jeffrey Smerage, Justin Stebbing, Leon W.M.M. Terstappen, José Vidal-Martínez, Rita Zamarchi, Karthik Giridhar, Thomas W.P. Friedl, Minetta C. Liu. Clinical utility of repeated circulating tumor cell (CTC) enumeration as early treatment monitoring tool in metastatic breast cancer (MBC) - a global pooled analysis with individual patient data [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr GS4-08.

FGFR1 amplification or overexpression and hormonal resistance in luminal breast cancer: rationale for a triple blockade of ER, CDK4/6, and FGFR1

BACKGROUND

FGFR1 amplification, but not overexpression, has been related to adverse prognosis in hormone-positive breast cancer (HRPBC). Whether FGFR1 overexpression and amplification are correlated, what is their distribution among luminal A or B HRPBC, and if there is a potential different prognostic role for amplification and overexpression are currently unknown features. The role of FGFR1 inhibitors in HRPBC is also unclear.

METHODS

FGFR1 amplification (FISH) and overexpression (RNAscope) were investigated in a N = 251 HRPBC patients cohort and the METABRIC cohort; effects on survival and FISH-RNAscope concordance were determined. We generated hormonal deprivation resistant (LTED-R) and FGFR1-overexpressing cell line variants of the ER+ MCF7 and T47-D and the ER+, FGFR1-amplified HCC1428 cell lines. The role of ER, CDK4/6, and/or FGFR1 blockade alone or in combinations in Rb phosphorylation, cell cycle, and survival were studied.

RESULTS

FGFR1 overexpression and amplification was non-concordant in > 20% of the patients, but both were associated to a similar relapse risk (~ 2.5-fold; P < 0.05). FGFR1 amplification or overexpression occurred regardless of the luminal subtype, but the incidence was higher in luminal B (16.3%) than A (6.6%) tumors; P < 0.05. The Kappa index for overexpression and amplification was 0.69 (P < 0.001). Twenty-four per cent of the patients showed either amplification and/or overexpression of FGFR1, what was associated to a hazard ratio for relapse of 2.6 (95% CI 1.44-4.62, P < 0.001). In vitro, hormonal deprivation led to FGFR1 overexpression. Primary FGFR1 amplification, engineered mRNA overexpression, or LTED-R-acquired FGFR1 overexpression led to resistance against hormonotherapy alone or in combination with the CDK4/6 inhibitor palbociclib. Blocking FGFR1 with the kinase-inhibitor rogaratinib led to suppression of Rb phosphorylation, abrogation of the cell cycle, and resistance-reversion in all FGFR1 models.

CONCLUSIONS

FGFR1 amplification and overexpression are associated to similar adverse prognosis in hormone-positive breast cancer. Capturing all the patients with adverse prognosis-linked FGFR1 aberrations requires assessing both features. Hormonal deprivation leads to FGFR1 overexpression, and FGFR1 overexpression and/or amplification are associated with resistance to hormonal monotherapy or in combination with palbociclib. Both resistances are reverted with triple ER, CDK4/6, and FGFR1 blockade.

A multivariable prognostic score to guide systemic therapy in early-stage HER2-positive breast cancer: a retrospective study with an external evaluation

BACKGROUND

In early-stage HER2-positive breast cancer, escalation or de-escalation of systemic therapy is a controversial topic. As an aid to treatment decisions, we aimed to develop a prognostic assay that integrates multiple data types for predicting survival outcome in patients with newly diagnosed HER2-positive breast cancer.

METHODS

We derived a combined prognostic model using retrospective clinical-pathological data on stromal tumour-infiltrating lymphocytes, PAM50 subtypes, and expression of 55 genes obtained from patients who participated in the Short-HER phase 3 trial. The trial enrolled patients with newly diagnosed, node-positive, HER2-positive breast cancer or, if node negative, with at least one risk factor (ie, tumour size >2 cm, histological grade 3, lymphovascular invasion, Ki67 >20%, age ≤35 years, or hormone receptor negativity), and randomly assigned them to adjuvant anthracycline plus taxane-based combinations with either 9 weeks or 1 year of trastuzumab. Trastuzumab was administered intravenously every 3 weeks (8 mg/kg loading dose at first cycle, and 6 mg/kg thereafter) for 18 doses or weekly (4 mg/kg loading dose in the first week, and 2 mg/kg thereafter) for 9 weeks, starting concomitantly with the first taxane dose. Median follow-up was 91·4 months (IQR 75·1-105·6). The primary objective of our study was to derive and evaluate a combined prognostic score associated with distant metastasis-free survival (the time between randomisation and distant recurrence or death before recurrence), an exploratory endpoint in Short-HER. Patient samples in the training dataset were split into a training set (n=290) and a testing set (n=145), balancing for event and treatment group. The training set was further stratified into 100 iterations of Monte-Carlo cross validation (MCCV). Cox proportional hazard models were fit to MCCV training samples using Elastic-Net. A maximum of 92 features were assessed. The final prognostic model was evaluated in an independent combined dataset of 267 patients with early-stage HER2-positive breast cancer treated with different neoadjuvant and adjuvant anti-HER2-based combinations and from four other studies (PAMELA, CHER-LOB, Hospital Clinic, and Padova) with disease-free survival outcome data.

FINDINGS

From Short-HER, data from 435 (35%) of 1254 patients for tumour size (T1 vs rest), nodal status (N0 vs rest), number of tumour-infiltrating lymphocytes (continuous variable), subtype (HER2-enriched and basal-like vs rest), and 13 genes composed the final model (named HER2DX). HER2DX was significantly associated with distant metastasis-free survival as a continuous variable (p<0·0001). HER2DX median score for quartiles 1-2 was identified as the cutoff to identify low-risk patients; and the score that distinguished quartile 3 from quartile 4 was the cutoff to distinguish medium-risk and high-risk populations. The 5-year distant metastasis-free survival of the low-risk, medium-risk, and high-risk populations were 98·1% (95% CI 96·3-99·9), 88·9% (83·2-95·0), and 73·9% (66·0-82·7), respectively (low-risk vs high-risk hazard ratio [HR] 0·04, 95% CI 0·0-0·1, p<0·0001). In the evaluation cohort, HER2DX was significantly associated with disease-free survival as a continuous variable (HR 2·77, 95% CI 1·4-5·6, p=0·0040) and as group categories (low-risk vs high-risk HR 0·27, 0·1-0·7, p=0·005). 5-year disease-free survival in the HER2DX low-risk group was 93·5% (89·0-98·3%) and in the high-risk group was 81·1% (71·5-92·1).

INTERPRETATION

The HER2DX combined prognostic score identifies patients with early-stage, HER2-positive breast cancer who might be candidates for escalated or de-escalated systemic treatment. Future clinical validation of HER2DX seems warranted to establish its use in different scenarios, especially in the neoadjuvant setting.

FUNDING

Instituto Salud Carlos III, Save the Mama, Pas a Pas, Fundación Científica, Asociación Española Contra el Cáncer, Fundación SEOM, National Institutes of Health, Agenzia Italiana del Farmaco, International Agency for Research on Cancer, and the Veneto Institute of Oncology, and Italian Association for Cancer Research.