Treatment patterns of patients with HR+/HER2- metastatic breast cancer receiving CDK4/6 inhibitor-based regimens: a cohort study in the French nationwide healthcare database

PURPOSE

To assess real-world treatment patterns in patients diagnosed with hormone receptor positive (HR+), human epidermal growth factor receptor 2 negative (HER2-) metastatic breast cancer (mBC) who received cyclin-dependent kinase 4/6 (CDK4/6) inhibitors in combination with an aromatase inhibitor (AI) or fulvestrant at first line.

METHODS

Patient characteristics, treatment history, and outcomes data were extracted from the French 'Système National des Données de Santé' (SNDS) database for patients diagnosed with HR+/HER2- mBC between January 2014 and June 2019 and who received combination therapy with a CDK4/6 inhibitor and endocrine therapy. Kaplan-Meier methodology was used to assess time to next treatment (TTNT) and time to treatment discontinuation (TTTD).

RESULTS

The cohort comprised 6061 patients including 4032 patients who received CDK4/6 inhibitors + AIs and 2029 patients who received CDK4/6 inhibitors + fulvestrant. Median follow-up was 13.5 months (IQR 9.5-18.1). The median TTTD of first line treatment with CDK4/6 inhibitors + AIs and CDK4/6 inhibitors + fulvestrant was 17.3 months (95% CI 16.8-17.9) and 9.7 months (95% CI 9.0-10.2), respectively. Chemotherapy was the most common second line therapy. Median TTTD of subsequent treatment lines was progressively shorter following first line treatment with CDK4/6 inhibitors + AIs (2nd line: 4.6 months (95% CI 4.4-4.9) and with CDK4/6 inhibitors + fulvestrant (2nd line: 4.7 months (95% CI 4.3-5.1). TTNT was longer than TTTD across lines of therapy.

CONCLUSION

This real-world analysis confirms the effectiveness of CDK4/6 inhibitor-based regimens in French patients and highlights the frequent use of chemotherapy as second line therapy.

Could a Long-Acting Prodrug of SN-38 be Efficacious in Sacituzumab Govitecan-Resistant Tumors?

We previously proposed that sacituzumab govitecan (SG, Trodelvy®) likely acts as a simple prodrug of systemic SN-38 as well as an antibody drug conjugate (ADC). In the present commentary, we assess whether a long-acting SN-38 prodrug, such as PLX038, might be efficacious in SG-resistant patients. We first describe possible mechanisms of action of SG, with new insights on pharmacokinetics and TROP2 receptor occupancy. We argue that SG is not an optimal conventional ADC and that the amount of systemic SN-38 spontaneously hydrolyzed from the ADC is so high it must have activity. Then, we describe the concept of time-over-target as related to the pharmacology of SG and PLX038 as SN-38 prodrugs. To be clear, we are not in any way suggesting that PLX038 or any SN-38 prodrug is superior to SG as an anticancer agent. Clearly, SG has the benefit over antigen-independent SN-38 prodrugs in that it targets cells with the TROP2 receptor. However, we surmise that PLX038 should be a more efficacious and less toxic prodrug of systemic SN-38 than SG. Finally, we suggest possible mechanisms of SG resistance and how PLX038 might perform in the context of each. Taken together, we argue that-contrary to many opinions-SG does not exclusively act as a conventional ADC, and propose that PLX038 may be efficacious in some settings of SG-resistance.

Tolerance of Concurrent Adjuvant Radiation Therapy and Pembrolizumab for Triple Negative Breast Cancer: Real Life Experience

Purpose

The current standard-of-care management of locally advanced triple negative breast cancer (TNBC) is based on neoadjuvant chemo-immunotherapy with pembrolizumab, surgery, radiation therapy (RT), and adjuvant pembrolizumab. However, the safety of combining pembrolizumab with adjuvant breast RT has never been evaluated. This study evaluated the tolerance profile of concurrent pembrolizumab with adjuvant RT in patients with locally advanced TNBC.

Methods and Materials

This bicentric ambispective study included all the patients with early and locally advanced TNBC who received neoadjuvant chemo-immunotherapy with pembrolizumab and adjuvant RT as part of their treatment. The tolerance profile of adjuvant RT was evaluated and compared in patients who received concurrent pembrolizumab and in patients for whom pembrolizumab was withheld.

Results

Fifty-five patients were included between July 2021 and March 2023. Twenty-eight patients received adjuvant RT with concurrent pembrolizumab (RT+P group), and 27 patients had pembrolizumab withheld while receiving adjuvant RT (RT-only group). Two patients developed grade ≥3 toxicity (1 grade 3 pain in the RT+P group and 1 grade 3 radiodermatitis in the RT-only group), and there were no differences in terms of toxicity between the RT-only and the RT+P groups. No cardiac or pulmonary adverse event was reported during RT. With a median follow-up of 12 months (10-26), no patient relapsed.

Conclusions

In this study of limited size, the authors did not find a difference between the RT-only and RT+P groups in terms of toxicity. More studies and longer follow-up may add to the strength of this evidence.

[18F]FDG PET/CT for predicting triple-negative breast cancer outcomes after neoadjuvant chemotherapy with or without pembrolizumab

PURPOSE

To determine if pretreatment [18F]FDG PET/CT could contribute to predicting complete pathological complete response (pCR) in patients with early-stage triple-negative breast cancer (TNBC) undergoing neoadjuvant chemotherapy with or without pembrolizumab.

METHODS

In this retrospective bicentric study, we included TNBC patients who underwent [18F]FDG PET/CT before neoadjuvant chemotherapy (NAC) or chemo-immunotherapy (NACI) between March 2017 and August 2022. Clinical, biological, and pathological data were collected. Tumor SUVmax and total metabolic tumor volume (TMTV) were measured from the PET images. Cut-off values were determined using ROC curves and a multivariable model was developed using logistic regression to predict pCR.

RESULTS

N = 191 patients were included. pCR rates were 53 and 70% in patients treated with NAC (N = 91) and NACI (N = 100), respectively (p < 0.01). In univariable analysis, high Ki67, high tumor SUVmax (> 12.3), and low TMTV (≤ 3.0 cm3) were predictors of pCR in the NAC cohort while tumor staging classification (< T3), BRCA1/2 germline mutation, high tumor SUVmax (> 17.2), and low TMTV (≤ 7.3 cm3) correlated with pCR in the NACI cohort. In multivariable analysis, only high tumor SUVmax (NAC: OR 8.8, p < 0.01; NACI: OR 3.7, p = 0.02) and low TMTV (NAC: OR 6.6, p < 0.01; NACI: OR 3.5, p = 0.03) were independent factors for pCR in both cohorts, albeit at different thresholds.

CONCLUSION

High tumor metabolism (SUVmax) and low tumor burden (TMTV) could predict pCR after NAC regardless of the addition of pembrolizumab. Further studies are warranted to validate such findings and determine how these biomarkers could be used to guide neoadjuvant therapy in TNBC patients.

Modeling the novel SERD elacestrant in cultured fulvestrant-refractory HR-positive breast circulating tumor cells

PURPOSE

Metastatic hormone receptor-positive (HR+) breast cancer initially responds to serial courses of endocrine therapy, but ultimately becomes refractory. Elacestrant, a new generation FDA-approved oral selective estrogen receptor degrader (SERD) and antagonist, has demonstrated efficacy in a subset of women with advanced HR+breast cancer, but there are few patient-derived models to characterize its effect in advanced cancers with diverse treatment histories and acquired mutations.

METHODS

We analyzed clinical outcomes with elacestrant, compared with endocrine therapy, among women who had previously been treated with a fulvestrant-containing regimen from the recent phase 3 EMERALD Study. We further modeled sensitivity to elacestrant, compared with the currently approved SERD, fulvestrant in patient-derived xenograft (PDX) models and cultured circulating tumor cells (CTCs).

RESULTS

Analysis of the subset of breast cancer patients enrolled in the EMERALD study who had previously received a fulvestrant-containing regimen indicates that they had better progression-free survival with elacestrant than with standard-of-care endocrine therapy, a finding that was independent estrogen receptor (ESR1) gene mutations. We modeled elacestrant responsiveness using patient-derived xenograft (PDX) models and in ex vivo cultured CTCs derived from patients with HR+breast cancer extensively treated with multiple endocrine therapies, including fulvestrant. Both CTCs and PDX models are refractory to fulvestrant but sensitive to elacestrant, independent of mutations in ESR1 and Phosphatidylinositol-4,5-Bisphosphate 3-Kinase Catalytic Subunit Alpha (PIK3CA) genes.

CONCLUSION

Elacestrant retains efficacy in breast cancer cells that have acquired resistance to currently available ER targeting therapies. Elacestrant may be an option for patients with HR+/HER2- breast cancer whose disease progressed on fulvestrant in the metastatic setting.

TRANSLATIONAL RELEVANCE

Serial endocrine therapy is the mainstay of management for metastatic HR+breast cancer, but acquisition of drug resistance highlights the need for better therapies. Elacestrant is a recently FDA-approved novel oral selective estrogen receptor degrader (SERD), with demonstrated efficacy in the EMERALD phase 3 clinical trial of refractory HR+breast cancer. Subgroup analysis of the EMERALD clinical trial identifies clinical benefit with elacestrant in patients who had received prior fulvestrant independent of the mutational status of the ESR1 gene, supporting its potential utility in treating refractory HR+breast cancer. Here, we use pre-clinical models, including ex vivo cultures of circulating tumor cells and patient-derived xenografts, to demonstrate the efficacy of elacestrant in breast cancer cells with acquired resistance to fulvestrant.

PET/CT and SPECT/CT Imaging of HER2-Positive Breast Cancer

HER2 (Human Epidermal Growth Factor Receptor 2)-positive breast cancer is characterized by amplification of the HER2 gene and is associated with more aggressive tumor growth, increased risk of metastasis, and poorer prognosis when compared to other subtypes of breast cancer. HER2 expression is therefore a critical tumor feature that can be used to diagnose and treat breast cancer. Moving forward, advances in HER2 in vivo imaging, involving the use of techniques such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT), may allow for a greater role for HER2 status in guiding the management of breast cancer patients. This will apply both to patients who are HER2-positive and those who have limited-to-minimal immunohistochemical HER2 expression (HER2-low), with imaging ultimately helping clinicians determine the size and location of tumors. Additionally, PET and SPECT could help evaluate effectiveness of HER2-targeted therapies, such as trastuzumab or pertuzumab for HER2-positive cancers, and specially modified antibody drug conjugates (ADC), such as trastuzumab-deruxtecan, for HER2-low variants. This review will explore the current and future role of HER2 imaging in personalizing the care of patients diagnosed with breast cancer.

Abstract P4-07-24: Circulating tumor cells enumeration and Health Related Quality of Life of patients treated with first-line chemotherapy for HER2 negative metastatic breast cancer

Background: In patients with metastatic breast cancer (mBC), Circulating Tumor Cells (CTC) counts have a strong prognostic impact on progression free survival (PFS) and overall survival (OS). Changes 4 weeks after the start of a new line of therapy, inform on treatment efficacy. Despite improvements in systemic treatment, metastatic BC remains mainly uncurable with alteration of health-related quality of life (HRQOL) during the course of the disease. The aim of this work was to assess impact of clinical factors and biological factors as CTC on HRQOL. Methods: The French cohort COMET is a prospective study including first line HER2 negative patients receiving weekly paclitaxel and bevacizumab according to EMA approved combination. The aim of this cohort was to evaluate clinical, biological and radiological parameters associated with patients’ outcome (CTC, CEC, serum markers, ctDNA, pharmacogenomic polymorphisms, metabolomic parameters, visceral fat assessed by initial CTscan, serum estradiol level, and quality of life). HRQOL was assessed at baseline, at every cycle until progression and then every 3 months up to death using the EORTC QLQ-C30 questionnaire and its breast cancer specific module, the EORTC QLQ-BR23. Five dimensions of HRQOL were analyzed for the primary analyses: Global health status (GHS), physical functioning (PF), Emotional functioning (EF), fatigue (FA) and pain (PA). Time until definitive deterioration (TUDD) in HRQOL was defined as the interval between inclusion and the first decrease in HRQOL score ≥ 5 compared to baseline HRQOL score with no further improvement or in case of death. CTC counts were determined using the standard CellSearch system [Menarini Silicon Biosystems]. Results: Out of 510 patients included in COMET study, 432 patients with available HRQOL data were analyzed in this study. At baseline, patients reported a mean score for GHS of 57.6 (SD=22.7), for PF of 75.8 (23.2), for EF of 62.2 (25.8), for FA of 42.2 (29.60) and for PA of 38.1 (31.5). The Median TUDDs for the 5 targeted dimensions was 10.1 months [7.5-16.9] for GHS, 6.1 months [4.1-8.9] for PF, 21.6 [18.7-31.2] for EF, 10.8 [6.2-16.6] for FA and 13.6[10.1-22.5] months for PA. CTC counts were available in 261 patients at base line and in 229 patients after 4 weeks of treatment, before second cycle of chemotherapy. CTC high count was independent of main clinical and biological characteristics except lobular subtype. We confirmed the poor outcome of patients with high CTC count at base line and after one cycle of treatment with the threshold of &gt; 4CTC/7.5 ml of blood. Out of the 5 dimensions of HRQOL, TUDD of EF was significantly correlated with a high CTC level at base line (p=0.0262) and even more with still an elevated count of CTC after one cycle of chemotherapy(p=0.0137). There was no association of CTC with the other dimensions of HRQOL. Conclusion: This is the first study ever reporting an analysis of QoL and CTC. We observed an association of high CTC count with one component of HRQOL scale. This suggests that CTC could be complementary to clinical factors that could influence HRQOL in HER2 negative metastatic BC treated with first line chemotherapy.

Citation Format: Jean-Yves Pierga, Oumar Billa, Sandrine Dabakuyo, Jérôme Lemonnier, Frédérique Berger, Olivier Trédan, William Jacot, Anthony Gonçalves, Marc Debled, Christelle Levy, Christelle Jouannaud, Marie-Ange Mouret-Reynier, Jean-Marc Ferrero, Florence Dalenc, Fatima-Zohra Toumi, Franck Bonnetain, Francois-Clement Bidard, Shufang Renault. Circulating tumor cells enumeration and Health Related Quality of Life of patients treated with first-line chemotherapy for HER2 negative metastatic 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 P4-07-24.

Abstract P5-02-19: ctDNA as dynamic marker of response to fulvestrant and everolimus in CDK4/6 inhibitor-pretreated ER+ HER2- metastatic breast cancer patients: a prospective study

ctDNA as dynamic marker of response to fulvestrant and everolimus in CDK4/6 inhibitor-pretreated ER+ HER2- metastatic breast cancer patients: a prospective study. Background The combination of fulvestrant with everolimus is recognized by NCCN and ESMO guidelines as a valid second line treatment option for ER+ HER2- metastatic breast cancer (mBC), upon progression on CDK4/6 inhibitor. The underlying evidence consists in a single randomized phase 2 trial (PrE0102, JCO 2018), in which N=66 patients allocated to fulvestrant and everolimus achieved a median PFS of 10.3 months (95%CI [7.6-13.8]). However, none of PrE0102 patients were pre-treated with CDK4/6 inhibitors. We set up a prospective study to document the PFS achieved by fulvestrant and everolimus in the pre-treated patients and investigated the clinical validity of ctDNA early changes as pharmacodynamic marker. Methods Eligible patients had ER+ HER2- mBC and had to be pre-treated by CDK4/6 inhibitor. Upon the signature of informed consent, patients were enrolled in the prospective observational ALCINA study (NCT02866149) and had their blood drawn at baseline (prior to treatment start), after 1 month on treatment, at first radiological assessment (3-4 months) and at disease progression. DNA from archived tumor tissue sample (or, when missing, from plasma obtained at baseline) was subjected to a large panel next generation sequencing. ctDNA levels were then assessed on the matched serial plasma samples by targeting the identified somatic mutation(s) with droplet digital PCR (ddPCR). Associations between clinicopathological characteristics, ctDNA levels and prospectively registered patient outcomes (PFS and OS) were then analyzed. Results Fifty-seven patients have been included, with a median age of 56.8 years. N=30 (52.6%) patients had ≥3 metastatic sites and N=34 (59.6%) had visceral metastases. Most patients (N=48, 84.2%) had only one prior line of treatment in the metastatic setting. After a median follow-up of 17.7 months, the median PFS was 6.9 months (95%CI[5.3-10.7]) and the median OS was 38.3 months (95%CI[26.9-NA]). The ORR was 33.3% (N=19 PR, no CR) whereas N=22 (38.6%) patients had a stable disease at best response. In the subgroup of N=22 (38.6%) patients with somatic PIK3CA mutations, median PFS was 3.1 months (95%CI[2.87-10.9]), while median OS was not reached. In multivariate analysis, somatic PIK3CA mutation was associated with a trend toward a shorter PFS (HR=1.84, 95%CI[0.97-3.99], p=0.06) and OS (HR=2.23, 95%CI[0.88-5.69], p=0.09). Duration of CDK4/6 inhibitor treatment had no overt impact on PFS (HR=0.68, 95%CI[0.38-1.22], p=0.2). Ten (19.6%) patients discontinued everolimus due to toxicity and 17 (29.9%) had at least one dose reduction due to an adverse event. The most grade 3 adverse event were mucositis (10.5%) and hypertriglyceridemia (3.5%), only 1 patient had a grade 3 pneumopathy. At least one mutation trackable by ddPCR was found in N=48 patients. As of July 2022, ctDNA levels have been analyzed in 34 patients (PIK3CAmut: N=19; ESR1mut: N=6; TP53mut: N=4; AKTmut: N=2; CUX1mut: N=1; GATA3mut: N=1; PTENmut: N=1). At baseline, N= 26/34 patients (76.5%) of patients had detectable ctDNA levels. Baseline ctDNA positivity had no prognostic impact on PFS (HR=0.93, 95%CI[0.4-2.13], p=0.86). ctDNA monitoring in the whole cohort will be available for the congress. Conclusion To our knowledge, this is the first prospective study to evaluate the efficacy of fulvestrant-everolimus after progression on CDK4/6 inhibitor. Efficacy data on 57 patients shows that fulvestrant-everolimus is an active regimen in this population. The PFS observed under fulvestrant-everolimus in patients with PIK3CA-mutant mBC appears shorter than previouly reported with alpelisib in the BYLIEVE study. Results of ctDNA to monitor the individual response to therapy will be presented at the congress.

Citation Format: Antoine Vasseur, Caroline Hego, Wissam Taka, Olfa Trabelsi-Grati, Florence Lerebours, Jean-Yves Pierga, Delphine Loirat, Etienne Brain, Paul COTTU, Marie-Paule Sablin, Luc Cabel, Benjamin Renouf, Shufang Renault, Francois-Clement Bidard. ctDNA as dynamic marker of response to fulvestrant and everolimus in CDK4/6 inhibitor-pretreated ER+ HER2- metastatic breast cancer patients: a prospective 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 P5-02-19.

Abstract P3-06-09: Real-world toxicity of pembrolizumab-based neoadjuvant regimen in patients with early triple negative breast cancer

Background Pembrolizumab (pembro, anti-PD-1 antibody) combined to chemotherapy (CT) in neoadjuvant/adjuvant setting has demonstrated its efficacy for early triple negative breast cancer (eTNBC). Pembro obtained FDA marketing authorization on July 26, 2021 and is available in France through the French Early Access Program. Methods We built an ambispective cohort that aimed to evaluate the efficacy and safety of the pembro-CT combination in the real world setting in patients with eTNBC. This study included patients treated from September 2021 to May 2022, at Institut Curie, France. Patients provided written authorization to report their clinical data. We report here the safety results. Results Between September 2021 and May 2022, 51 patients were included. Median age was 49 years [29; 68]. Germline mutations were recorded in 8 patients (22.2% of 36 tested patients). All pts were ECOG PS 0 or 1. Baseline clinical TNM stage were T1 (8 pts, 15.7%), T2 (30 pts, 58.9%), T3 (7 pts, 13.7%) and T4 (6 pts, 11.7%). Out of 37 pts (72.5%) with radiological axillary lymph node involvement, 19 pts (51.4%) had positive node involvement confirmed by guided fine needle aspiration. SBR grade 2 and 3 were observed in 9 (17.6%) and 42 (82.4%) pts, respectively. HER2 score was 0 or 1+/2+(FISH neg) for 31 (60.8 %) and 20 pts (39.2 %), respectively. A CPS score ≥ 10 was observed in 19 pts (50% of 38 tested patients). The CT backbone was a combination of carboplatin (Cb) plus weekly paclitaxel (wP) 4 courses (with Cb regimen AUC 5 q3W (81.1%), AUC4 q3w (5.4%) and AUC1,5 q1w (13.5%), and wP 80 mg/m²), followed by standard AC60/600 q3w for 4 courses. Out of the 37 pts (72.5%) who completed the Cb + wP 4 courses, all experienced adverse events (AEs), including 21 pts (56.8%) with at least 1 grade ≥ 3 AE (anemia 5.4%, thrombopenia 5.4%, neutropenia 51.5%, neuropathy 2.7%). Transfusion support was needed for 8 pts (21.6%). Grade ≥ 2 neuropathy occurred in 3 pts (8.1 %). Dose reduction and drug discontinuation were performed in 9 (24.3%) and 5 pts (13.5%), respectively. On the entire cohort, 15 pts (29.4%) had IrAE all grades: dysthyroidism (6 pts, 11.7%), skin toxicity (2 pts, 3.9%), adrenal insufficiency (1 pt, 2%), hypophysitis (1 pt, 2%), immune-allergic nephropathy (1 pt, 2%), suspicion of myocarditis (1 pt, 2%), hepatitis (1 pt, 2%) and ophthalmologic AE (1 pt, 2%). Consequently, after a median follow up of 5 months, pembro postponement and permanent discontinuation were performed in 7 (13,7%) and 5 pts (9,8%), respectively. At abstract submission 6 pts had breast surgery (pCR in 5 pts = 83.3%). Conclusions Our real-world data are consistent with the results of the KEYNOTE-522 trial in terms of patients characteristics. We observed a very high rate of hematological and immune related adverse events, frequently leading to dose reduction or discontinuation, underlying the need for a very close clinical management of those patients. Updated data including toxicity during the whole neoadjuvant sequence and pCR rate will be presented at the meeting.

Citation Format: Delphine Loirat, Emilie ARNAUD, Khaoula ALAOUI, Pauline VAFLARD, Sinen KORBI, Dalila MEZIANI, Lucie THIBAULT, Romain-Pacome DESMARIS, Jean-Guillaume FERON, Jean-Yves Pierga, Francois-Clement Bidard, Paul COTTU. Real-world toxicity of pembrolizumab-based neoadjuvant regimen in patients with early triple negative 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 P3-06-09.

Abstract OT1-01-02: EMBER-4: A phase 3 adjuvant trial of imlunestrant vs standard endocrine therapy (ET) in patients with ER+, HER2- early breast cancer (EBC) with an increased risk of recurrence who have previously received 2 to 5 years of adjuvant ET

Background: Adjuvant ET has been the standard of care for patients with estrogen receptor-positive (ER+), human epidermal growth factor receptor 2-negative (HER2-) EBC. A significant proportion of patients with increased risk still experience disease relapse despite available ET and more optimum ET is needed to prevent patients developing incurable metastatic cancer. Distant recurrence risk ranges from 20% to 40% after 5 years of adjuvant ET, depending on clinicopathological (clin-path) features at diagnosis. Consequently, there is a need to further optimize adjuvant treatment, particularly in those patients who are at increased risk of recurrence. Imlunestrant is an orally bioavailable selective estrogen receptor degrader (SERD) with pure antagonistic properties and the potential to overcome ET resistance. In early phase trials, imlunestrant monotherapy showed favorable safety with pharmacokinetic (PK) exposures exceeding fulvestrant and preliminary efficacy in ER+, HER2- advanced breast cancer patients (EMBER, Jhaveri 2022) along with robust biological/pharmacodynamic activity and tolerability in EBC (EMBER-2, Neven). Trial Design: EMBER-4 is a randomized, open-label, global phase 3 study comparing imlunestrant versus physicians’ choice of ET, in patients who are at an increased risk of recurrence based on clin-path features and who have received 2 to 5 years of standard adjuvant ET. Approximately 6,000 patients will be randomized 1:1 to receive imlunestrant (400 mg daily) for 5 years or physicians’ choice of adjuvant ET (tamoxifen or an aromatase inhibitor, AI, dosed per label). Study treatment duration is 5 years. Males and pre-/peri-menopausal women will receive concomitant treatment with a GnRH agonist if receiving imlunestrant or an AI. Stratification factors include time from initial adjuvant ET, use of prior adjuvant cyclin dependent kinase 4/6 inhibitors, nodal status, menopausal status, and geographic region. Eligibility criteria: Eligible patients are adult males and females (pre-, peri- or postmenopausal) with ER+, HER2- EBC who have completed definitive locoregional therapy and have received 2 to 5 years of prior adjuvant ET without disease recurrence, but who are at increased risk of recurrence based on clin-path features at diagnosis. Prior (neo) adjuvant chemotherapy and/or targeted therapy with a CDK4/6- or PARP- inhibitor is permitted. Study endpoints: The primary endpoint is invasive disease-free survival (IDFS), excluding second non-breast primary invasive cancers. Key secondary endpoints include distant relapse-free survival, overall survival, IDFS including second non-breast primary invasive cancers, safety, PK and patient reported outcomes. Recruitment for EMBER-4 begins globally in Q4 2022.

Citation Format: Komal Jhaveri, Joyce O’Shaughnessy, Fabrice Andre, Matthew P. Goetz, Nadia Harbeck, Miguel Martín, Francois-Clement Bidard, Zachary M. Thomas, Suzanne Young, Roohi Ismail-Khan, Lillian M. Smyth, Michael Gnant. EMBER-4: A phase 3 adjuvant trial of imlunestrant vs standard endocrine therapy (ET) in patients with ER+, HER2- early breast cancer (EBC) with an increased risk of recurrence who have previously received 2 to 5 years of adjuvant ET [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 OT1-01-02.

Design of SERENA-6, a phase III switching trial of camizestrant in ESR1-mutant breast cancer during first-line treatment

ESR1 mutation (ESR1m) is a frequent cause of acquired resistance to aromatase inhibitor (AI) plus cyclin-dependent kinase 4 and 6 inhibitors (CDK4/6i), which is a first-line therapy for hormone-receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) advanced breast cancer (ABC). Camizestrant is a next-generation oral selective estrogen receptor degrader (SERD) that in a phase II study significantly improved progression-free survival (PFS) over fulvestrant (also a SERD) in ER+/HER2- ABC. SERENA-6 (NCT04964934) is a randomized, double-blind, phase III study evaluating the efficacy and safety of switching from an AI to camizestrant, while maintaining the same CDK4/6i, upon detection of ESR1m in circulating tumor DNA before clinical disease progression on first-line therapy for HR+/HER2- ABC. The aim is to treat ESR1m clones and extend the duration of control of ER-driven tumor growth, delaying the need for chemotherapy. The primary end point is PFS; secondary end points include chemotherapy-free survival, time to second progression event (PFS2), overall survival, patient-reported outcomes and safety.

Abstract P6-10-06: A preoperative window-of-opportunity study of imlunestrant in estrogen receptor-positive, HER2-negative early breast cancer: Results from the EMBER-2 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. In a phase 1 study, imlunestrant monotherapy showed favourable safety, pharmacokinetics (PK) and preliminary efficacy in heavily pre-treated ER-positive (ER+) advanced breast cancer patients (Jhaveri ASCO 2022). Here, we present pharmacodynamic (PD) data from the preoperative window of opportunity (WOO) study (EMBER-2, NCT04647487), evaluating the biological activity of imlunestrant monotherapy in ER+, HER2-negative (HER2-) early breast cancer (EBC).

Methods: Post-menopausal women with stage I–III operable ER+ (&gt;50%) or Allred score &gt;5, HER2- untreated EBC ≥1 cm in diameter were randomized 1:1 to imlunestrant 400 mg once daily (QD) or imlunestrant 800 mg QD for 15 days (treatment window of -2 to +7 days) up to the surgery date. Pre- and on-treatment tumor samples were compared for changes in PD biomarkers. Primary study objective was change in ER expression (measured by IHC and quantified by H-score). Secondary objectives were change in progesterone receptor (PR) expression (measured by IHC and quantified by H-score) and Ki-67 (measured by IHC and expressed by percentage positive scoring) along with evaluation of safety and tolerability.

Results: From Apr 28, 2021, to Mar 11, 2022, 58 patients were enrolled of which 54 were biomarker-evaluable for ER expression (400 mg: n = 28; 800 mg: n = 26). Patient demographics and tumor characteristics for all enrolled patients were similar across cohorts, with a median age of 64 years (50-83), 72% invasive ductal carcinoma (IDC), 28% invasive lobular carcinoma (ILC), 59% stage I, 36% stage II and 5% stage III disease. 91% of the patients had a compliance rate higher than 80%. Among biomarker evaluable patients, relative reduction in PD biomarkers after a median of 15 days (range 13 to 23 days) of treatment are presented in Table 1. There was no significant difference in PD biomarker modulation noted between the two imlunestrant doses (400 mg vs 800 mg) or based on tumor histology (IDC, ILC). Imlunestrant was well tolerated. There were no discontinuations due to adverse events (AEs). Treatment-related AEs (TRAEs) were mainly grade 1, most commonly: fatigue (10%), diarrhea (9%), hot flushes (7%), and nausea (5%). There were no TRAEs of diarrhea and nausea observed at the 400 mg dose. No grade 3 or higher TRAEs were reported.

Conclusion: Imlunestrant demonstrated evidence of target engagement along with consistent biological activity across all evaluated dose levels and was well tolerated in an EBC population, further supporting continued adjuvant development in the ongoing EMBER-4 study. Additional biomarker analyses for the EMBER-2 study are also planned.

Table 1. Relative reduction in PD biomarkers from Baseline to Day 15

Citation Format: Patrick Neven, Nicole Stahl, Maria Vidal, Miguel Martín, Nadia Harbeck, Peter A. Kaufman, Francois-Clement Bidard, Peter A. Fasching, Philippe Aftimos, Erika Hamilton, Stacey Carter, Peter Schmid, Duncan Wheatley, Manali Bhave, Kelly K. Hunt, Swati A. Kulkarni, Roohi Ismail-Khan, Claudia Karacsonyi, Shawn T. Estrem, Umut Ozbek, Bastien Nguyen, Eva Ciruelos. A preoperative window-of-opportunity study of imlunestrant in estrogen receptor-positive, HER2-negative early breast cancer: Results from the EMBER-2 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 P6-10-06.

Abstract GS3-09: GS3-09 Circulating Tumor Cells-driven choice of first line therapy for ER+ HER2- metastatic breast cancer: overall survival analysis of the randomized STIC CTC trial

Background: High circulating tumor cell (CTC) count (CTChigh) is a strong adverse prognostic factor in patients with metastatic breast cancer (mBC). In the STIC CTC trial (NCT01710605), run before the introduction of CDK4/6 inhibitors for ER+/HER2- mBC, we showed that CTC count (CTC arm) was non inferior to clinician’s choice (standard arm) on progression-free survival (PFS) to guide first line treatment selection between chemotherapy (CT) and endocrine therapy (ET) (Bidard et al., JAMA Oncol 2021). Of note, patients who had treatment escalated from ET (a priori clinician choice) to CT in the CTC arm, had a significantly longer PFS. We report here overall survival (OS) results of this multicenter CTC clinical utility trial.

Methods: In the CTC arm, N=377 patients had their treatment determined by baseline CTC count: CT if CTChigh (≥5 CTCs/7.5 mL, CellSearch®), ET if CTClow. In the standard arm (N=378 patients), the choice was left to the investigator: CT if clinical high risk (Clinhigh), ET if clinical low risk (Clinlow). Therefore, patients with discordant Clinlow/CTChigh or Clinhigh/CTClow profiles had their first line treatment escalated from ET (standard arm) to CT (CTC arm) or de-escalated from CT (standard arm) to ET (CTC arm), respectively. Patients with concordant Clinlow/CTClow and Clinhigh/CTChigh profiles received ET and CT in both arms, respectively.

Results: Among 755 randomized patients, N=189 (25.0%) had a Clinlow/CTChigh profile, N=103 (13.6%) Clinhigh/CTClow, N=363 (48.2%) Clinlow/CTClow and N=100 (13.2%) Clinhigh/CTChigh. OS was analyzed after a median follow-up of 57 months and 382 events (50.6%). In the Clinlow/CTChigh subgroup, CT in the CTC arm led a longer OS (mOS: 51.8 months [43.3-NR]) than ET in the standard arm (35.4 months [30.4-45.4]; HR=0.53 [0.36-0.78], p=0.001). In patients Clinhigh/CTClow, no significant difference was observed whether they received CT (standard arm) or ET (CTC arm) (45.9 months [36.3-59.8] vs 49.4 months [35.4-65.4]; HR=0.88 [0.51-1.51], p=0.63). Pooling the two discordant groups (Clinlow/CTChigh or Clinhigh/CTClow), the CTC-driven strategy was superior to the clinician-driven treatment decision (HR=0.63 [0.46-0.86], p=0.02). Pooling all concordant and discordant groups together, a median OS of 45.5 (95%CI=[40.9-51.1]) and 51.3 months [46.8-55.1] was observed in the standard and CTC arms, respectively (HR=0.84 [0.69-1.03], p=0.10).

Conclusions: Prognostic information brought by CTC or standard factors is discordant in 40% of patients with ER+ HER2- mBC. In case of a discordant estimate, the STIC CTC trial shows the superiority on OS of the CTC-driven treatment decision strategy. These results also suggest a possible clinical utility of CTC to adjust systemic treatment for mBC in second and later lines, after progression on CDK4/6 inhibitors.

Funding:The study was funded by Institut Curie; the French National Cancer Institute (INCa), as part of the Programme de Soutien aux Techniques Innovantes Coûteuses 2011 (STIC 2011); and Menarini Silicon Biosystems (Castel Maggiore, Italy).

Abstract GS3-01: GS3-01 EMERALD phase 3 trial of elacestrant versus standard of care endocrine therapy in patients with ER+/HER2- metastatic breast cancer: Updated results by duration of prior CDK4/6i in metastatic setting

Background: In patients (pts) with ER+/HER2− metastatic breast cancer (MBC) following progression on prior endocrine and CDK4/6i therapy, the EMERALD trial demonstrated significantly prolonged progression-free survival (PFS) and a manageable safety profile for elacestrant versus standard of care endocrine therapy (SoC). Benefit was observed in all pts and in pts with ESR1 mutant MBC (ESR1-mut). EMERALD is the only oral SERD monotherapy pivotal trial where all pts were pretreated with CDK4/6 inhibitor (CDK 4/6i). Here, we examine the impact of duration of prior CDK4/6i on PFS.

Methods: EMERALD (NCT03778931) is a randomized, open-label, phase 3 trial that enrolled pts with ER+/HER2- MBC who previously had 1-2 lines of endocrine therapy, mandatory CDK4/6i, and ≤1 chemotherapy; prior treatment with fulvestrant was allowed. Patients were randomized 1:1 to elacestrant (400 mg orally daily) or SoC (investigator’s choice of aromatase inhibitor or fulvestrant). If randomized to the control arm, patients who received prior fulvestrant were to receive an aromatase inhibitor, and vice versa. If two CDK4/6i were used in the metastatic setting (n=40), the cumulative duration was calculated.

Results: A total of 478 pts were randomized (228 with ESR1-mut) between Feb 2019 – Oct 2020 (n=239, elacestrant; n=239, SoC). Overall survival was not yet mature, as of September 2nd 2022. Updated PFS results show statistically significant results in favor of elacestrant, both in all pts and in pts with ESR1-mut. The duration of prior CDK4/6i in the metastatic setting was positively associated with PFS, the longer the duration of prior CDK4/6i in the metastatic setting (n=465), the longer the PFS on elacestrant versus SoC (Table 1).

Updated safety data were consistent with previously reported results. Most of the adverse events (AEs), including nausea, were grade 1 and 2, and only 3.4% and 0.9% of the pts discontinued trial therapy because of an AE on elacestrant and SoC, respectively. A low percentage of pts received an antiemetic; 8.0%, 3.7%, and 10.3%, on elacestrant, fulvestrant, and AI, respectively. No hematological safety signal was observed and none of the patients in either of the two treatment arms had sinus bradycardia.

Conclusions: EMERALD is the first phase 3 trial to demonstrate a significant PFS improvement versus SoC in all pts and in the subgroup with ESR1 mutations in pts with ER-positive/HER2-negative MBC with 1-2 prior lines of endocrine treatment ± one line of chemotherapy. Elacestrant demonstrated longer PFS versus SOC that was positively associated with the duration of prior treatment with CDK4/6i, which was more pronounced in pts with ESR1-mut MBC. In this 2nd and 3rd line setting, elacestrant was well tolerated with significantly longer PFS versus SoC, highlighting its potential role as a therapeutic option for pts with ER+/HER2- MBC.

Table 1: PFS estimates in the elacestrant and SoC arms based on different cut-off points for the duration of prior CDK4/6i.

Citation Format: Aditya Bardia, Francois-Clement Bidard, Patrick Neven, Guillermo Streich, Alberto J. Montero, Frederic Forget, Marie-Ange Mouret-Reynier, Joo Hyuk Sohn, Donatienne Taylor, Kathleen K. Harnden, Hung Khong, Judit Kocsis, Florence Dalenc, Patrick Dillon, Sunil Babu, Simon Waters, Ines Deleu, Jose Angel García-Sáenz, Emilio Bria, Marina Elena Cazzaniga, Philippe Aftimos, Javier Cortés, Giulia Tonini, Tarek Sahmoud, Nassir Habboubi, Krzysztof Grzegorzewski, Virginia Kaklamani. GS3-01 EMERALD phase 3 trial of elacestrant versus standard of care endocrine therapy in patients with ER+/HER2- metastatic breast cancer: Updated results by duration of prior CDK4/6i in metastatic setting [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 GS3-01.

Abstract PD17-02: ctDNA Molecular Response based on breast cancer driver mutations predicts progression in aromatase inhibitor-sensitive first line treatment of oestrogen receptor-positive (ER+) HER2-negative (HER2-) advanced breast cancer

Background: The combination of a CDK4/6 inhibitor and an aromatase inhibitor (AI) is the gold standard for AI-sensitive first line treatment of ER+ HER2- advanced breast cancer. Nevertheless, some patients progress rapidly and may benefit from alternative strategies. Early ctDNA dynamics have been shown to predict disease course in several clinical situations. Here, we use samples from the PADA-1 trial to assess this strategy for patients receiving AI and palbociclib as first line treatment. PADA-1 was designed to assess the clinical utility of sequential analysis of ctDNA for emerging ESR1 mutations to trigger an early switch from AI plus palbociclib to fulvestrant plus palbociclib treatment. The study included 1,017 patients and was positive on its primary end-point. The objective of this translational study was to analyze the predictive value of 4-week molecular response (MR) for patient progression. Material & Method: First, a CLIA-validated targeted next-generation sequencing-based test (Guardant360 Response) was used to characterize changes in ctDNA level via detection of somatic single-nucleotide variants (SNVs), insertion/deletion mutations (indels), and gene fusions in 74 genes frequently mutated in cancer. A second analysis was restricted to cancer-associated mutations in 11 genes commonly mutated in breast cancer (PIK3CA, GATA3, TP53, AKT1, ERBB2, BRCA1, BRCA2, ATM, ESR1, PALB2 and RB1). The threshold for molecular response was defined as ≥ 50% decrease in ctDNA (MR score &lt; 0.5). Subjects with ctDNA levels below the test’s limit of quantitation (ctDNA-low) were considered molecular responders. Results: 372 subjects with matched baseline and 4-weeks samples were available for analysis. Of these, 134 subjects (36%) were ctDNA-low, and 238 subjects (64%) quantifiable. Among the quantifiable subjects, 183 (77%) were molecular responders (MR+, MR &lt; 0.5), and 55 (23%) were not (MR–, MR ≥ 0.5). PFS was moderately improved for both MR+ and ctDNA-low relative to MR– (HR=0.61 (95%CI 0.44-0.85), p&lt; 0.01) over the full 29 months of follow up. Differential PFS event rate was observed only in the first 8 months following ctDNA assessment; during this time MR+ and ctDNA-low were associated with more significantly decreased risk of progression (HR 0.24, 95% CI 0.13 – 0.43, p=0.0001). Limiting ctDNA assessment to genes commonly mutated in breast cancer enhanced the predictive power of MR (HR=0.08, 95% CI 0.04 0.17, p&lt; 0.001, for MR+ and ctDNA-low vs. MR– across 8 months post-assessment); however, fewer samples were quantifiable by this method (169 [45%] quantifiable; 203 [55%] ctDNA-low). Combining MR status with additional molecular features (e.g.tumor mutational burden and maximum mutation allele fraction) did not improve prediction of non-response. Conclusion: Changes in ctDNA fraction during the first weeks of treatment are predictive of long term clinical benefit on an individual patient basis, particularly during the first year of therapy. Adjusting the MR threshold and/or limiting to genes known to be relevant in the specific tumor can tailor the assessment of ctDNA change to specific clinical scenarios where greater sensitivity or specificity may be required. The identification of patients at high risk for early clinical failure at the onset of treatment may allow for therapy escalation and/or change to improve outcome in this population. Funding: Pfizer and Guardant Health

Citation Format: Caroline Bailleux, Thomas Bachelot, Francois-Clement Bidard, Anne-Claire Hardy-Bessard, Ivan Bièche, Anne Pradines, Florian Clatot, thibault DE LA MOTTE ROUGE, Jean-Luc Canon, Barbara Pistilli, Kyle Chang, Katie J. Quinn, Heather L. Gustafson, Florence Dalenc, Cyril Foa, Hanifa Ammarguellat, Chantal Bernard-Marty, Brigitte Lucas, Sophie Barthier, Fabrice Lorchel, Olivier Gisserot, Laurent Arnould, Marjorie Mauduit, Jérôme Lemonnier, Frédérique Berger, Suzette Delaloge, Fabrice Andre. ctDNA Molecular Response based on breast cancer driver mutations predicts progression in aromatase inhibitor-sensitive first line treatment of oestrogen receptor-positive (ER+) HER2-negative (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 PD17-02.

Alpelisib and fulvestrant in PIK3CA-mutated hormone receptor-positive HER2-negative advanced breast cancer included in the French early access program

SOLAR-1 and BYLieve trials documented the efficacy of the PI3K-inhibitor alpelisib in pre-treated PIK3CA-mutant, hormone receptor-positive, HER2-negative (HR+/HER2-) advanced breast cancer (ABC) patients. We report here real-life data of patients prospectively registered in the French alpelisib early access program (EAP) opened to PIK3CA-mutant HR+/HER2- ABC patients treated with alpelisib and fulvestrant. Primary endpoint was PFS by local investigators using RECIST1.1. Eleven centers provided individual data on 233 consecutive patients. Patients had received a median number of 4 (range: 1-16) prior systemic treatments for ABC, including CDK4/6 inhibitor, chemotherapy, fulvestrant and everolimus in 227 (97.4%), 180 (77.3%), 175 (75.1%) and 131 (56.2%) patients, respectively. After a median follow-up of 7.1 months and 168 events, median PFS was 5.3 months (95% CI: 4.7-6.0). Among 186 evaluable patients, CBR at 6 months was 45.3% (95% CI: 37.8-52.8). In multivariable analysis, characteristics significantly associated with a shorter PFS were age < 60 years (HR = 1.5, 95% CI = 1.1-2.1), >5 lines of prior treatments (HR = 1.4, 95% CI = 1.0-2.0) and the C420R PI3KCA mutation (HR = 4.1, 95% CI = 1.3-13.6). N = 91 (39.1%) patients discontinued alpelisib due to adverse events. To our knowledge, this is the largest real-life assessment of alpelisib efficacy. Despite heavy pre-treatments, patients derived a clinically relevant benefit from alpelisib and fulvestrant.

Elacestrant (oral selective estrogen receptor degrader) Versus Standard Endocrine Therapy for Estrogen Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Negative Advanced Breast Cancer: Results From the Randomized Phase III EMERALD Trial

PURPOSE

Patients with pretreated estrogen receptor (ER)-positive/human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer have poor prognosis. Elacestrant is a novel, oral selective ER degrader that demonstrated activity in early studies.

METHODS

This randomized, open-label, phase III trial enrolled patients with ER-positive/HER2-negative advanced breast cancer who had one-two lines of endocrine therapy, required pretreatment with a cyclin-dependent kinase 4/6 inhibitor, and ≤ 1 chemotherapy. Patients were randomly assigned to elacestrant 400 mg orally once daily or standard-of-care (SOC) endocrine monotherapy. Primary end points were progression-free survival (PFS) by blinded independent central review in all patients and patients with detectable ESR1 mutations.

RESULTS

Patients were randomly assigned to elacestrant (n = 239) or SOC (n = 238). ESR1 mutation was detected in 47.8% of patients, and 43.4% received two prior endocrine therapies. PFS was prolonged in all patients (hazard ratio = 0.70; 95% CI, 0.55 to 0.88; P = .002) and patients with ESR1 mutation (hazard ratio = 0.55; 95% CI, 0.39 to 0.77; P = .0005). Treatment-related grade 3/4 adverse events occurred in 7.2% receiving elacestrant and 3.1% receiving SOC. Treatment-related adverse events leading to treatment discontinuations were 3.4% in the elacestrant arm versus 0.9% in SOC. Nausea of any grade occurred in 35.0% receiving elacestrant and 18.8% receiving SOC (grade 3/4, 2.5% and 0.9%, respectively).

CONCLUSION

Elacestrant is the first oral selective ER degrader demonstrating a significant PFS improvement versus SOC both in the overall population and in patients with ESR1 mutations with manageable safety in a phase III trial for patients with ER-positive/HER2-negative advanced breast cancer.

Oral Etoposide and Trastuzumab Use for HER2-Positive Metastatic Breast Cancer: A Retrospective Study from the Institut Curie Hospitals

BACKGROUND

The TOP2A and ERBB2 genes are co-amplified in about 40% of HER2 positive (HER2+) breast cancers. Oral etoposide (VP16), an inhibitor of topoisomerase-II (encoded by TOP2A), has demonstrated clinical activity in metastatic breast cancer (MBC). The benefit of oral VP16 combined with trastuzumab (VP16-T) in HER2+ MBC has not yet been evaluated.

METHODS

Patients treated at the Institut Curie Hospitals with VP16-T for HER2+ MBC were retrieved by an in silico search. Progression-free survival (PFS), overall survival (OS), response rate, prolonged PFS (defined as at least 6 months), clinical benefit, and toxicity were assessed. The co-amplification of ERBB2 and TOP2A was assessed by shallow whole genome sequencing on tumor tissue whenever available.

RESULTS

Forty-three patients received VP16-T after a median number of six prior treatment lines for HER2+ MBC. Median PFS and OS were 2.9 months (95% CI [2.4-4.7]) and 11.3 months (95% CI [8.3-25.0]), respectively. Three patients had a complete response, while 12/40 (30%) experienced clinical benefit. Only three patients stopped treatment for toxicity. Seven (35%) patients displayed a TOP2A/ERBB2 co-amplification. No statistically significant correlation was found between outcome and TOP2A/ERBB2 co-amplification.

CONCLUSION

Our analysis suggests a favorable efficacy and toxicity profile for VP16-T in patients with heavily pretreated HER2+ MBC.

Real-Time Detection of ESR1 Mutation in Blood by Droplet Digital PCR in the PADA-1 Trial: Feasibility and Cross-Validation with NGS

The clinical actionability of circulating tumor DNA requires sensitive detection methods with a short turnaround time. In the PADA-1 phase 3 trial (NCT03079011), metastatic breast cancer patients treated with an aromatase inhibitor and palbociclib were screened every 2 months for activating ESR1 mutations in blood (bESR1_mut). We report the feasibility of the droplet digital polymerase chain reaction (ddPCR) and cross-validation with next-generation sequencing (NGS). bESR1_mut testing was centralized in two platforms using the same ddPCR assay. Results were reported as copies/mL of plasma and mutant allele frequency (MAF). We analyzed 200 positive ddPCR samples with an NGS assay (0.5-1% sensitivity). Overall, 12,552 blood samples were collected from 1017 patients from 83 centers. Among the 12,525 available samples with ddPCR results, 11,533 (92%) were bESR1_mut-negative. A total of 267 patients newly displayed bESR1_mut (26% patients/2% samples) with a median copy number of 14/mL (range: 4-1225) and a median MAF of 0.83% (0.11-35), 648 samples (20% patients/5% samples) displayed persistent bESR1_mut, and 77 (<1%) samples encountered a technical failure. The median turnaround time from blood drawing to result notification was 13 days (Q1:9; Q3:21 days). Among 200 ddPCR-positive samples tested, NGS detected bESR1_mut in 168 (84%); 25 of the 32 cases missed by NGS had low MAF and/or low coverage. In these 200 samples, bESR1_mut MAF by both techniques had an excellent intraclass correlation coefficient (ICC = 0.93; 95% CI [0.85; 0.97]). These results from a large-scale trial support the feasibility and accuracy of real-time bESR1_mut tracking by ddPCR, opening new opportunities for therapeutic interventions.

Abstract GS2-02: Elacestrant, an oral selective estrogen receptor degrader (SERD), vs investigator’s choice of endocrine monotherapy for ER+/HER2- advanced/metastatic breast cancer (mBC) following progression on prior endocrine and CDK4/6 inhibitor therapy: Results of EMERALD phase 3 trial

Background: Endocrine therapy(ET) plus CDK4/6 inhibitor (i) is the mainstay for the management of estrogenreceptor-positive (ER+)/HER2- mBC. However, most patients (pts) with ER+ mBCeventually experience disease progression, including development of ESR1mutations (mESR1). Elacestrant, an oral SERD, demonstrated preclinical activity,and clinical activity in a phase 1 trial in ER+ mBC, including responses in ptswith prior fulvestrant, CDK4/6i, and mESR1tumors (Bardia JCO 2021).. Methods: EMERALD(NCT03778931), a multicenter, international, randomized, open-label, controlledphase 3 trial, enrolled postmenopausal pts with ER+/HER2- mBC who had received 1-2prior lines of ET and ≤1 line of chemotherapy in the mBC setting and had prior progressionon a ET plus CDK4/6i. Pts were randomized 1:1 to elacestrant (400 mg orallydaily) or standard of care (SOC; investigator’s choice of fulvestrant or anaromatase inhibitor). Stratification factors included mESR1 status (by central lab), priorfulvestrant exposure, and presence of visceral disease. The study had 2 primary endpoints of progression-free survival (PFS), by blindedindependent review committee, in pts withtumors harboring mESR1 and in all pts (mESR1 or mESR1 notdetected). Secondary endpoints included: overall survival (OS), safety, tolerability,and quality of life. An alpha-value of 0.0475 was used to determine statisticalsignificance (2-sided using the truncated Hochberg procedure).. Results: EMERALD enrolled 477 pts(228 with mESR1) between Feb 2019 - Oct 2020, with 239 pts randomized toreceive elacestrant vs 238 pts to SOC. Demographics and disease characteristicswere well-balanced across treatment arms [median age: 63 yrs vs 63.5 yrs; 2prior lines: 46% vs 40.8%; prior CDK4/6i: 100% in both arms]. The study met bothprimary endpoints. There was a 30% reduction in the risk of progression ordeath in the elacestrant arm in all pts (HR=0.697 [95% CI: 0.552, 0.88]; P=0.0018),and a 45% (HR=0.546 [95% CI: 0.387, 0.768]; P=0.0005) reduction in therisk of progression or death in pts with mESR1.For both endpoints, results in key prespecified subgroups, including visceral metastases,number of prior lines of therapy, pretreatment with fulvestrant, and geographicalregion, were consistent with the overall outcome. The PFS rate at 12 months was 22.32% (95% CI: 15.24%, 29.40%)with elacestrant vs 9.42% (95% CI: 4.02%, 14.81%) with SOC in all pts, and26.76% (95% CI: 16.17%, 37.36%) vs 8.19% (95% CI: 1.26%, 15.12%) in the mESR1 subgroup. The prespecified interim OS analysis plannedat the time of the final PFS analysis (allocated2-sided alpha level of 0.0001) demonstrated a trend in favor of elacestrant inall pts (HR=0.751 [95% CI: 0.542, 1.038]; P=0.0821) and in pts with mESR1(HR=0.592 [95% CI: 0.361, 0.958]; P=0.0325). The final OS analysisis expected next year. Common (&gt;10%) treatment-related adverse events (AEs) withelacestrant vs SOC included: nausea (25.3% vs 8.7%), vomiting (11% vs 2.6%), and fatigue (11% vs 7.9%), mostlygrade 1/2. Treatment-emergent AEs leading to discontinuation of elacestrant orSOC were infrequent in both arms (6.3% and 4.4%). Grade ≥3 treatment-relatedAEs in the elacestrant arm vs SOC were 7.2% vs 3.1%, mainly driven by nausea(2.1% vs 0.9%). There were no treatment-related deaths in either group.. Conclusions:Elacestrant is the first oral SERD to demonstrate a statistically significantand clinically meaningful improvement of PFS vs SOC in a randomized phase 3study in pts with ER+/HER2- mBC in the 2nd/3rd-linesetting, including those whose tumors harbor mESR1. Elacestrant was well tolerated and hasthe potential to become the new standard of care for pts with ER+/HER2- mBC.

Citation Format: Aditya Bardia, Patrick Neven, Guillermo Streich, Alberto J. Montero, Frédéric Forget, Marie-Ange Mouret-Reynier, Joo Hyuk Sohn, Peter Vuylsteke, Kathleen K. Harnden, Hung Khong, Judit Kocsis, Florence Dalenc, Virginia Kaklamani, Patrick Dillon, Sunil Babu, Simon Waters, Ines Deleu, José García-Sáenz, Emilio Bria, Marina Cazzaniga, Janice Lu, Philippe Aftimos, Javier Cortes, Shubin Liu, Dirk Laurent, Maureen G. Conlan, Francois-Clement Bidard. Elacestrant, an oral selective estrogen receptor degrader (SERD), vs investigator’s choice of endocrine monotherapy for ER+/HER2- advanced/metastatic breast cancer (mBC) following progression on prior endocrine and CDK4/6 inhibitor therapy: Results of EMERALD phase 3 trial [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 GS2-02.

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.

A DNA methylation-based liquid biopsy for triple-negative breast cancer

Here, we present a next-generation sequencing (NGS) methylation-based blood test called methylation DETEction of Circulating Tumour DNA (mDETECT) designed for the optimal detection and monitoring of metastatic triple-negative breast cancer (TNBC). Based on a highly multiplexed targeted sequencing approach, this assay incorporates features that offer superior performance and included 53 amplicons from 47 regions. Analysis of a previously characterised cohort of women with metastatic TNBC with limited quantities of plasma (<2 ml) produced an AUC of 0.92 for detection of a tumour with a sensitivity of 76% for a specificity of 100%. mDETECT_TNBC was quantitative and showed superior performance to an NGS TP53 mutation-based test carried out on the same patients and to the conventional CA15-3 biomarker. mDETECT also functioned well in serum samples from metastatic TNBC patients where it produced an AUC of 0.97 for detection of a tumour with a sensitivity of 93% for a specificity of 100%. An assay for BRCA1 promoter methylation was also incorporated into the mDETECT assay and functioned well but its clinical significance is currently unclear. Clonal Hematopoiesis of Indeterminate Potential was investigated as a source of background in control subjects but was not seen to be significant, though a link to adiposity may be relevant. The mDETECT_TNBC assay is a liquid biopsy able to quantitatively detect all TNBC cancers and has the potential to improve the management of patients with this disease.

Total metabolic tumor volume and spleen metabolism on baseline [18F]-FDG PET/CT as independent prognostic biomarkers of recurrence in resected breast cancer

PURPOSE

We evaluated whether biomarkers on baseline [¹⁸F]-FDG PET/CT are associated with recurrence after surgery in patients with invasive breast cancer of no special type (NST).

METHODS

In this retrospective single-center study, we included consecutive patients with non-metastatic breast cancer of NST who underwent [¹⁸F]-FDG PET/CT before treatment, including surgery, between 2011 and 2016. Clinicopathological data were collected. Tumor SUVmax, total metabolic tumor volume (TMTV), and spleen- and bone marrow-to-liver SUVmax ratios (SLR, BLR) were measured from the PET images. Cut-off values were determined using predictiveness curves to predict 5-year recurrence-free survival (5y-RFS). A multivariable prediction model was developed using Cox regression. The association with stromal tumor-infiltrating lymphocytes (TILs) levels (low if <50%) was studied by logistic regression.

RESULTS

Three hundred and three women were eligible, including 93 (31%) with triple-negative breast carcinoma. After a median follow-up of 6.2 years, 56 and 35 patients experienced recurrence and death, respectively. The 5y-RFS rate was 86%. In multivariable analyses, high TMTV (>20 cm3) and high SLR (>0.76) were associated with shorter 5y-RFS (HR 2.4, 95%CI 1.3-4.5, and HR 1.9, 95%CI 1.0-3.6). In logistic regression, high SLR was the only independent factor associated with low stromal TILs (OR 2.8, 95%CI 1.4-5.7).

CONCLUSION

High total metabolic tumor volume and high spleen glucose metabolism on baseline [¹⁸F]-FDG PET/CT were associated with poor 5y-RFS after surgical resection in patients with breast cancer of NST. Spleen metabolism was inversely correlated with stromal TILs and might be a surrogate for an immunosuppressive tumor microenvironment.

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.

Clinical utility of circulating tumour cell-based monitoring of late-line chemotherapy for metastatic breast cancer: the randomised CirCe01 trial

BACKGROUND

CirCe01 trial aimed to assess the clinical utility of circulating tumour cell (CTC)-based monitoring in metastatic breast cancer (MBC) patients beyond the third line of chemotherapy (LC).

METHODS

CirCe01 was a prospective, multicentre, randomised trial (NCT01349842) that included patients with MBC after two systemic LC. Patients with ≥5 CTC/7.5 mL (CellSearch®) were randomised between the CTC-driven and the standard arm. In the CTC arm, changes in CTC count were assessed at the first cycle of each LC; patients in whom CTC levels predicted early tumour progression had to switch to a subsequent LC.

RESULTS

Greater than or equal to 5 CTC/7.5 mL were observed in N = 101/204 patients. In the CTC arm (N = 51), 43 (83%) and 18 (44%) patients completed CTC monitoring in the third and fourth lines, respectively, and 18 (42%) and 11 (61%) of these patients, respectively, had no CTC response. Thirteen (72%) and 5 (46%) of these patients underwent early switch to the next LC. Overall survival was not different between the two arms (hazard ratio = 0.95, 95% confidence interval = [0.6;1.4], p = 0.8). In subgroup analyses, patients with no CTC response who switched chemotherapy experienced longer survival than patients who did not.

CONCLUSIONS

Due to the limited accrual and compliance, this trial failed to demonstrate the clinical utility of CTC monitoring.

CLINICAL TRIAL REGISTRATION

NCT, NCT01349842, https://clinicaltrials.gov/ct2/show/NCT01349842 , registered 9 May 2011.

Characteristics and outcome of breast cancer-related microangiopathic haemolytic anaemia: a multicentre study

BACKGROUND

Cancer-related microangiopathic haemolytic anaemia (MAHA) is a rare but life-threatening paraneoplastic syndrome. Only single cases or small series have been reported to date. We set up a retrospective multicentre study focusing on breast cancer-related MAHA.

METHODS

Main inclusion criteria were known diagnosis of breast cancer, presence of schistocytes and either low haptoglobin or cytopenia and absence of any causes of MAHA other than breast cancer, including gemcitabine- or bevacizumab-based treatment. Patient characteristics, treatments and outcome were retrieved from digital medical records.

RESULTS

Individual data from 54 patients with breast cancer-related MAHA were obtained from 7 centres. Twenty-three (44%) patients had a breast tumour with lobular features, and most primary tumours were low grade (grade I/II, N = 39, 75%). ER+/HER2-, HER2+ and triple-negative phenotypes accounted for N = 33 (69%), N = 7 (15%) and N = 8 (17%) cases, respectively. All patients had stage IV cancer at the time of MAHA diagnosis. Median overall survival (OS) was 28 days (range 0-1035; Q1:10, Q3:186). Independent prognostic factors for early death (≤ 28 days) were PS > 2 (OR = 7.0 [1.6; 31.8]), elevated bilirubin (OR = 6.9 [1.1; 42.6]), haemoglobin < 8.0 g/dL (OR = 3.7 [0.9; 16.7]) and prothrombin time < 50% (OR = 9.1 [1.2; 50.0]). A score to predict early death displayed a sensitivity of 86% (95% CI [0.67; 0.96]), a specificity of 73% (95% CI [0.52; 0.88]) and an area under the curve of 0.90 (95% CI [0.83; 0.97]).

CONCLUSIONS

Breast cancer-related MAHA appears to be a new feature of invasive lobular breast carcinoma. Prognostic factors and scores may guide clinical decision-making in this serious but not always fatal condition.

Abstract 3390: Predictive and prognostic value of circulating tumor DNA (ctDNA) compared to circulating tumor cells (CTC) in a prospective cohort of metastatic breast cancer patients: The UCBG COMET trial

Background: In metastatic breast cancer (MBC), monitoring circulating tumor DNA (ctDNA) can detect mutation associated with resistance to treatment and its variations reflect changes in tumor burden. We prospectively monitored CTC and ctDNA during first line chemotherapy for MBC.

Methods: The French cohort COMET is a prospective study including first line HER2- negative pts receiving weekly paclitaxel and bevacizumab. Blood samples were obtained at baseline (BL) and before the second cycle of chemotherapy (C2). ctDNA was analyzed by targeted resequencing (custom panel 220kb) SNV (28 genes + 8 promoters and CNA (18 genes).

Results: For ctDNA, out of 196 pts analyzed, 147 had at least one somatic mutation (SNV) detected in plasma (75%). Despite no complete overlap, 24 pts (12%) had no CTC nor ctDNA detected at baseline. Including Copy Number Variation analysis (CNV), the number of patients without detectable ctDNA at baseline could be reduced to 18 (9%). The average number of mutations per pt was 2.4 (range 1 to 9). Median Allelic Frequency (MAF) was 9.1%. Most commonly mutated genes were TP53 and GATA3 with 14% and 7% of all mutations, respectively. TP53 mutations were detected in 31 % of patients and were associated with a shorter progression-free and overall survival. PI3KCA mutations were detected in 23.2% of the pts, were correlated with presence of bone metastasis and had no prognostic value. ESR1 was mutated in 10.6% of the pts, restricted to the ER+ subgroup and had no impact on overall survival. At baseline, CTC and ctDNA levels were correlated (r = 0.40, p &lt; 0.0001). CTC detection was correlated with TP53 mutations detection but not with mutations PI3KCA or ESR1. Only 68 pts (36%) had detectable ctDNA at C2 with a MAF of 2% (0.3%-40%). 52.8% of patients positive for ctDNA at D1C1 became negative at D1C2 and only one negative at baseline became positive at C2.

Correlation rate with CTC was the same after one cycle of chemotherapy (r = 0.40). Median follow-up was 53 months and median OS was 32 months. At multivariate analysis, triple negative status, detectable ctDNA at C2, CTC ≥5 at C2 and grade 3 on primary tumor were independent prognostic for OS.

Conclusion: Early decrease of CTC and/or ctDNA after one cycle of chemotherapy are independent predictive markers of favorable outcome. Compared to CTC, ctDNA allows monitoring of tumor burden during chemotherapy and specific detection of targetable mutations as PI3KCA, HER2 or BRCA.

Citation Format: Jean-Yves Pierga, Amanda Silveira, Elodie Girard, Veronique Lorgis, Marie-Laure Tanguy, Benoit Albaud, Olivier Tredan, Coraline Dubot, Caroline Hego, William Jacot, Anthony Goncalves, Marc Debled, Christelle Levy, Jean-Marc Ferrero, Christelle Jouannaud, Marie-Ange Mouret-Reynier, Florence Dalenc, Sylvain Baulande, Jerome Lemonnier, Frederique Berger, Francois-Clement Bidard, Charlotte Proudhon. Predictive and prognostic value of circulating tumor DNA (ctDNA) compared to circulating tumor cells (CTC) in a prospective cohort of metastatic breast cancer patients: The UCBG COMET trial [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3390.

Abstract 5372: HER2 expression on tumor-derived extracellular vesicles and circulating tumor cells in metastatic breast cancer

Tumor-derived extracellular vesicles (tdEVs) and circulating tumor cells (CTCs) in blood of metastatic cancer patients associate with poor outcome. In this study, we explored the human epidermal growth factor receptor 2 (HER2) expression on CTCs and tdEVs of metastatic breast cancer patients.

Blood samples from 98 patients (IC 2006-04 study) were originally processed with the CellSearch® system using the CTC kit and anti-HER2 as an additional marker in the staining cocktail. CTCs and tdEVs were automatically enumerated from the generated CellSearch image datasets using the open-source ACCEPT software. The HER2 status of the tissue was assessed by fluorescence in situ hybridization (FISH).

The inclusion of anti-HER2 increased the percentage of informative samples with ≥1 detectable CTC and tdEV from 89% and 99% to 95 and 100%, respectively. CTCs and tdEVs were subdivided based on their cytokeratin (CK) and HER2 phenotype into CK+HER2-, CK-HER2+ and CK+HER2+. Inter- and intra- patient heterogeneity was found regarding the phenotype of CTCs and tdEVs with the majority of patients having all different subclasses present. CK- CTCs and tdEVs correlated equally well with clinical outcome as CK+ CTCs and tdEVs. Use of ≥7% HER2+CK+ tdEVs can predict HER2 expression of the tissue with 74% sensitivity and specificity, whereas the respective use of ≥23% HER2+CK+ CTCs leads to 65% sensitivity and 66% specificity.

HER2 can be detected on CTCs and tdEVs not expressing CK, which have similar clinical relevance to CTCs and tdEVs expressing CK. tdEVs perform better than CTCs in predicting the HER2 status of the tissue.

Funded by the NWO Applied and Engineering Sciences Cancer-ID project #14190, the EUFP7 CTCTrap project #305341 and the EU IMI CANCER-ID project # 115749-1.

Citation Format: Afroditi Nanou, Leonie L. Zeune, Francois-Clement Bidard, Jean-Yves Pierga, Leon W. Terstappen. HER2 expression on tumor-derived extracellular vesicles and circulating tumor cells in metastatic breast cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5372.

HER2 expression on tumor-derived extracellular vesicles and circulating tumor cells in metastatic breast cancer

Background

Tumor-derived extracellular vesicles (tdEVs) and circulating tumor cells (CTCs) in the blood of metastatic cancer patients associate with poor outcomes. In this study, we explored the human epidermal growth factor receptor 2 (HER2) expression on CTCs and tdEVs of metastatic breast cancer patients.

Methods

Blood samples from 98 patients (CLCC-IC-2006-04 study) were originally processed with the CellSearch® system using the CTC kit and anti-HER2 as an additional marker in the staining cocktail. CTCs and tdEVs were automatically enumerated from the generated CellSearch images using the open-source ACCEPT software.

Results

CTCs and tdEVs were subdivided based on their cytokeratin (CK) and HER2 phenotype into CK+HER2−, CK−HER2+, and CK+HER2+. The inclusion of anti-HER2 increased the percentage of informative samples with ≥ 1 detectable CTC from 89 to 95%. CK− CTCs and tdEVs correlated equally well with the clinical outcome as CK+ CTCs and tdEVs. Inter- and intra-patient heterogeneity was found for the CTC/tdEV phenotypes, and the presence of 2 or 3 classes of CTCs/tdEVs was associated with worse prognosis compared to a uniform CTC/tdEV phenotype present (1 class). The use of ≥ 7% HER2+CK+ tdEVs can predict HER2 expression of the tissue with 74% sensitivity and specificity using the HER2 amplification status of the primary tumor as a classification variable.

Conclusions

HER2 can be detected on CTCs and tdEVs not expressing CK, and these CK− CTCs/tdEVs have similar clinical relevance to CTCs and tdEVs expressing CK. tdEVs perform better than CTCs in predicting the HER2 status of the primary tissue. CTC and tdEV heterogeneity in the blood of patients is inversely associated with overall survival.

Plasma-derived cfDNA to reveal potential biomarkers of response prediction and monitoring in non-small cell lung cancer (NSCLC) patients on immunotherapy

9588

Background: Immune checkpoint inhibitors have shown promising results in many advanced cancers, but the response rate remains low. Various molecular and cellular biomarkers, such as elevated tumor-infiltrating cytotoxic T cells and Natural Killer (NK) cells at baseline, are associated with response. Blood-based biomarkers to predict or monitor response remain challenging to develop. Here we investigate the potential of cell-free DNA (cfDNA) biomarkers to predict response to the PD-1 immune checkpoint inhibitor nivolumab in patients with refractory metastatic non-small cell lung cancer (NSCLC). Methods: Plasma from stage IV NSCLC patients enrolled in ALCINA (NCT02866149) was collected before (baseline, BL, n = 30) and at week 8 (W8, n = 17) of nivolumab therapy. Response was determined using RECIST 1.1 (responders n = 5; non-responders n = 25). Whole-genome sequencing was performed to characterize cfDNA fragments. Tumor fraction (TF) was assessed using ichorCNA. Cellular composition was estimated by deconvolution of cfDNA co-fragmentation patterns, and transcription factor activity was estimated by measuring binding site accessibility across the genome. Results: Although estimated TF at baseline did not predict response to nivolumab, NK cell levels estimated by cell-mixture deconvolution were significantly higher in responders at BL (p < 0.05). Furthermore, estimated monocyte levels at W8 strongly correlated with overall survival (r = 0.75, p < 0.0005, HR = 15.02) and were significantly higher in responders (p < 0.05). By evaluating changes in transcription factor binding activity, we identified factors with greater accessibility in non-responders at baseline (DEAF1, THAP11) and W8 (DUX4, PDX-1). Conclusions: Plasma cfDNA signatures may be useful for response prediction and monitoring in NSCLC patients on immunotherapy. Our results suggest that changes in the immune system, as reflected by cellular composition and transcriptional activity inferred from cfDNA, may provide biological insights beyond TF alone that may benefit biomarker discovery and drug target identification.

Toronto Workshop on Late Recurrence in Estrogen Receptor-Positive Breast Cancer: Part 2: Approaches to Predict and Identify Late Recurrence, Research Directions

Late disease recurrence (more than 5 years after initial diagnosis) represents a clinical challenge in the treatment and management of estrogen receptor-positive breast cancer (BC). An international workshop was convened in Toronto, Canada, in February 2018 to review the current understanding of late recurrence and to identify critical issues that require future study. The underlying biological causes of late recurrence are complex, with the processes governing cancer cell dormancy, including immunosurveillance, cell proliferation, angiogenesis, and cellular stemness, being integral to disease progression. These critical processes are described herein as well as their role in influencing risk of recurrence. Moreover, observational and interventional clinical trials are proposed, with a focus on methods to identify patients at risk of recurrence and possible strategies to combat this in patients with estrogen receptor-positive BC. Because the problem of late BC recurrence of great importance, recent advances in disease detection and patient monitoring should be incorporated into novel clinical trials to evaluate approaches to enhance patient management. Indeed, future research on these issues is planned and will offer new options for effective late recurrence treatment and prevention strategies.

Toronto Workshop on Late Recurrence in Estrogen Receptor-Positive Breast Cancer: Part 1: Late Recurrence: Current Understanding, Clinical Considerations

Disease recurrence (locoregional, distant) exerts a significant clinical impact on the survival of estrogen receptor-positive breast cancer patients. Many of these recurrences occur late, more than 5 years after original diagnosis, and represent a major obstacle to the effective treatment of this disease. Indeed, methods to identify patients at risk of late recurrence and therapeutic strategies designed to avert or treat these recurrences are lacking. Therefore, an international workshop was convened in Toronto, Canada, in February 2018 to review the current understanding of late recurrence and to identify critical issues that require future study. In this article, the major issues surrounding late recurrence are defined and current approaches that may be applicable to this challenge are discussed. Specifically, diagnostic tests with potential utility in late-recurrence prediction are described as well as a variety of patient-related factors that may influence recurrence risk. Clinical and therapeutic approaches are also reviewed, with a focus on patient surveillance and the implementation of extended endocrine therapy in the context of late-recurrence prevention. Understanding and treating late recurrence in estrogen receptor-positive breast cancer is a major unmet clinical need. A concerted effort of basic and clinical research is required to confront late recurrence and improve disease management and patient survival.

Prognostic value of CEC count in HER2-negative metastatic breast cancer patients treated with bevacizumab and chemotherapy: a prospective validation study (UCBG COMET)

BACKGROUND

Proof of concept studies has reported that circulating endothelial cell (CEC) count may be associated with the outcome of HER2-negative metastatic breast cancer (mBC) patients treated by chemotherapy and the anti-VEGF antibody bevacizumab. We report the results obtained in an independent prospective validation cohort (COMET study, NCT01745757).

METHODS

The main baseline criteria were HER2-negative mBC, performance status 0-2 and no prior chemotherapy for metastatic disease. CECs were detected by CellSearch® from 4 ml of blood at baseline and after 4 weeks of weekly paclitaxel and bevacizumab therapy. CEC counts (considered both as a continuous variable and using the previously described 20 CEC/4 ml cutoff) were associated with clinical characteristics and progression-free survival (PFS).

RESULTS

CEC count was obtained in 251 patients at baseline and in 207 patients at 4 weeks. Median baseline CEC count was 22 CEC/4 ml (range 0-2231). Baseline CEC counts were associated with performance status (p = 0.02). No statistically significant change in CEC counts was observed between baseline and 4 weeks of therapy. High baseline CEC count was associated with shorter PFS in univariate and multivariate analyses (continuous: p < 0.001; dichotomized: HR 1.52, 95% CI [1.15-2.02], p = 0.004). CEC counts at 4 weeks had no prognostic impact.

CONCLUSION

This study confirms that CEC count may be associated with the outcome of mBC patients treated with chemotherapy and bevacizumab. However, discrepancies with previous reports in terms of both the timing of CEC count and the direction of the prognostic impact warrant further clinical investigation.

Actionability of HER2-amplified circulating tumor cells in HER2-negative metastatic breast cancer: the CirCe T-DM1 trial

BACKGROUND

In this prospective phase 2 trial, we assessed the efficacy of trastuzumab-emtansine (T-DM1) in HER2-negative metastatic breast cancer (MBC) patients with HER2-positive CTC.

METHODS

Main inclusion criteria for screening were as follows: women with HER2-negative MBC treated with ≥ 2 prior lines of chemotherapy and measurable disease. CTC with a HER2/CEP17 ratio of ≥ 2.2 by fluorescent in situ hybridization (CellSearch) were considered to be HER2-amplified (HER2_amp). Patients with ≥ 1 HER2_amp CTC were eligible for the treatment phase (T-DM1 monotherapy). The primary endpoint was the overall response rate.

RESULTS

In 154 screened patients, ≥ 1 and ≥ 5 CTC/7.5 ml of blood were detected in N = 118 (78.7%) and N = 86 (57.3%) patients, respectively. ≥1 HER2_amp CTC was found in 14 patients (9.1% of patients with ≥ 1 CTC/7.5 ml). Among 11 patients treated with T-DM1, one achieved a confirmed partial response. Four patients had a stable disease as best response. Median PFS was 4.8 months while median OS was 9.5 months.

CONCLUSIONS

CTC with HER2 amplification can be detected in a limited subset of HER2-negative MBC patients. Treatment with T-DM1 achieved a partial response in only one patient.

TRIAL REGISTRATION

NCT01975142, Registered 03 November 2013.

Abstract SY31-02: Clinical utility trials for CTC and ctDNA in ER+ advanced breast cancer

Background: In ER+ HER2- metastatic breast cancer (MBC) patients, current first line treatment options are either endocrine therapy (ET, given either as single agent or, more recently, in combination with cdk4/6 inhibitor) or chemotherapy (CT). Given its good risk/benefit ratio, endocrine therapy (ET) is the preferred 1stline therapy in these patients, but not all benefit from such strategy for which predictive biomarkers are lacking. During first line ET, resistance may also appear following the emergence of ESR1-mutated subclones. On grounds of prior clinical validity studies, the clinical utility of circulating tumor cells (CTC) and circulating tumor DNA (ctDNA) as a tool to improve the outcome of 1st line ER+ HER2- MBC patients has been / is investigated in large phase 3 trials.

CTC clinical utility trial: In the STIC CTC phase III trial (NCT01710605, coordinated by Institut Curie), the baseline CTC count (CellSearch, Menarini SB) was compared to the clinician's choice to treat patients with either single agent ET or frontline CT. N=778 ER+ HER2- MBC have been randomized between the CTC-driven choice to the clinician-driven choice. #60% of patients had a concordant prognostic evaluation. In the 2 subgroups (#40% of patients) with discordant treatment recommendations (depending on clinician or CTC count standpoint), frontline CT yielded significantly longer PFS. An unplanned analysis also suggested that CT was associated with a longer OS. Relying on CTC count as a modern prognostic biomarker, the STIC CTC trial was the first to identify potential ER+ HER2- MBC patients who might derive more benefit from frontline CT than from single agent ET, challenging current standards and deserving further studies.

ctDNA clinical utility trial: The phase III PADA-1 trial (NCT03079011, coordinated by Unicancer UCBG and GYNECO) is testing the clinical utility of real time ESR1mut detection (at baseline, at 1 month and then every 2 months) through ctDNA analysis in N=1000 ER+ HER2- MBC patients treated with aromatase inhibitor (AI) and palbociclib. Patients with rising ESR1mut in circulating tumor DNA (i.e. increasing or appearing mutations) during first line AI-palbociclib therapy are randomized in a second step between switching to Fulvestrant-palbociclib or keeping the same regimen (AI-palbociclib until disease progression, a cross-over being then proposed). ESR1mut are tracked in circulating DNA from up to 4ml of plasma by a ddPCR-based assay targeting E380, L536, Y537 and D538 hotspots (i.e. &gt;90% of known ESR1 activating mutations) with #0.1% sensitivity (Bidard et al, AACR 2018 #3867). Whereas the study is ongoing, preliminary results confirmed that ESR1mut is a rare event in untreated AI-"sensitive" ER+ HER2- MBC patients and primarily associated with a prior use of AI in the adjuvant setting. Interestingly, in most MBC patients with ESR1mut detected at baseline, ESR1mut became undetectable after 1 month of AI-Palbociclib therapy, suggesting that this combination may retain early antitumor efficacy.

Discussion: Demonstrating clinical utility is paramount for new cancer biomarkers such as CTC and ctDNA. Large prospective interventional trials are however required, such as those discussed here.

Citation Format: Francois-Clement Bidard. Clinical utility trials for CTC and ctDNA in ER+ advanced breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr SY31-02.

Abstract CT140: Circulating tumor cells as a tool to guide first line therapy in metastatic breast cancer: subgroup analyses of the STIC CTC Phase III utility trial

Background: Endocrine therapy (ET) is the preferred 1st line therapy in ER+ HER2- metastatic breast cancer (MBC) patients, but not all benefit from such strategy for which predictive biomarkers are lacking. Prior studies showed that circulating tumor cells (CTC) count is the strongest prognostic factor beyond PS in that population. The STIC CTC trial (NCT01710605) assessed whether CTC count could drive the choice between frontline ET or chemotherapy (CT, with or without ET maintenance).

Methods: For this multicenter phase 3 non-inferiority trial, main inclusion criteria were: ER+ HER2- MBC with no prior therapy, PS≤2, no contra-indication to ET or CT, informed consent. Patients were randomized 1:1 between clinically-driven choice (single agent ET if clinicallow, CT if clinicalhigh, as decided by physician based on clinical factors, blinded to CTC results) or a CTC-driven choice [ET if CTClow (&lt;5 CTCs/7.5mL), CT if CTChigh (≥5 CTCs/7.5mL)]. The primary objective was treatment efficacy ([PFS hazard ratio (HR)], non-inferiority being established if the upper bound of the PFS HR 2-sided 90%CI is &lt;1.25; secondary objectives included subgroup analyses (CTC status, patient characteristics) and OS.

Results: In this trial, 778 patients were randomized between both strategies. Of all patients, 71.0%, 26.6% and 2.4% were considered as endocrine-sensitive, with secondary or with primary endocrine resistance, respectively. In both arms (clinically- and CTC-driven), prognostic evaluation by physician/CTCs and allocated treatments were as follows: (i) clinicallow/CTClow 46.5% and 48.6% of patients, all treated with ET. (ii) clinicalhigh/CTChigh 14.0% and 13.0%, all treated with CT. (iii) clinicallow/CTChigh 26.1% and 24.2%, treated with ET or CT respectively. (iv) clinicalhigh/CTClow 13.4% and 14.0%, treated with CT or ET respectively. CTC-driven strategy met the primary endpoint, yielding a non-inferior PFS (median: 17 months; 95%CI [15.4-20.3] vs 18 months 95%CI[13.9-23.3]). In the 2 discordant subgroups, preplanned analyses showed the following results: in the clinicallow/CTChigh subgroup, patients treated with CT had a significantly longer PFS than those treated with ET (15.6 months, 95%CI [12.2-22.7] vs 10.5 months, 95%CI [7.3-15.4], log rank p=0.002). In the clinicalhigh/CTClow subgroup, patients treated with CT had a non-significant PFS advantage over patients treated with ET. Pooling these two subgroups of patients (N=292) with discordant treatment recommendations (depending on clinician or CTC count standpoint), an exploratory analysis showed that patients treated with CT frontline had significantly longer PFS (HR=0.66; 95%CI [0.51-0.85]) and OS (HR=0.65; 95%CI [0.43-0.98]); 2-year OS were 82.9% versus 74.7% in patients treated with CT (±maintenance ET) or ET, respectively.

Conclusion: This trial demonstrates the utility of CTC count to select 1st line therapy in ER+ HER2- MBC patients, especially in those for whom single agent ET is the recommended therapy based on clinical factors. With this modern prognostic biomarker, the STIC CTC trial is the first one to identify potential ER+ HER2- MBC patients who might derive more benefit from frontline CT followed by maintenance ET than from frontline ET, challenging current standards.

Funding: French Ministry of Health (PSTIC 2011); Menarini SB; Institut Curie.

Citation Format: Francois-Clement Bidard, William Jacot, Sylvain Dureau, Etienne Brain, Thomas Bachelot, Hugues Bourgeois, Anthony Goncalves, Sylvain Ladoire, Herve Naman, Florence Dalenc, Joseph Gligorov, Marc Espie, Christelle Levy, Jean-Marc Ferrero, Delphine Loirat, Paul Cottu, Veronique Dieras, Marie-Emmanuelle Legrier, Frederique Berger, Catherine Alix-Panabieres, Jean-Yves Pierga. Circulating tumor cells as a tool to guide first line therapy in metastatic breast cancer: subgroup analyses of the STIC CTC Phase III utility trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT140.

Immune-related toxicities in non-small cell lung cancer: Real-life predictors of outcome to checkpoint inhibitors?

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Background: Immune checkpoint inhibitors (ICIs) are approved for the treatment of non-small cell lung cancer (NSCLC) and are associated with immune-related adverse events (irAEs). However, real-life data on type, occurrence and kinetics of irAEs, and their predictive value on treatment outcome are lacking. Here, we report on the relation between irAEs, including endocrine irAEs, and outcome to anti-PD-/L-1 (programmed cell death protein-/ligand-1) ICIs. Methods: A total of 147 patients (pts), with locally advanced/metastatic NSCLC, treated with anti-PD-1 (N 140; 95%) or anti-PD-L1 agents (N 7; 5%) as ≥ 2 line treatment were included in two independent, prospective, cohorts at the Institut Curie (ALCINA-NCT02866149) and at Biella Hospital (Italy). PD-L1 status was assessed by immunohistochemistry (clone 22C3, Dako). Progression-free survival (PFS) and overall survival (OS) were estimated with Kaplan-Meier curves. Results: Median follow-up of 147 pts was 10.2 (range: 0.7-42.8) months; median age, 66 (35-85) years; 100 men (68%). After treatment initiation, irAEs were observed in 72 pts (49%). Thirty one (43%) pts had only endocrine irAEs, mostly thyroid dysfunctions (N 44, 61%). Pre-existing thyroid disease was present in only 6 pts (4%). Dermatologic toxicity in 21 (29%) pts was the next most frequent irAE, 22 (30%) pts had other types of irAEs. Among patients with irAEs, 61 (85%) had ≤ 2 coexisting irAEs, and 13 (18%) pts had > 2 irAEs. Most irAEs were G1 (63%) and G2 (18%). Onset and kinetics differed according to irAE type. There was no association between PD-L1 status and irAE occurrence. Median PFS was 7.2 and 4.2 months in irAEs vs no-irAEs group, respectively [HR 0.70 (95% CI 0.46;1.08), p 0.11]. Median OS in the irAEs group was 18.1 months vs 13.6 months no-irAEs group [HR 0.64 (95% CI 0.37;0.98), p 0.039]. Median OS in the endocrine-irAEs group was 23.5 vs 13.6 months in the no-irAEs group [HR 0.58 (0.74;3.92), p 0.2]. Conclusions: In this study, we show that irAEs – including endocrine type – are frequent in NSCLC pts treated with ICIs and that their occurrence is associated with a survival benefit.

Circulating Tumor Cells in Early Breast Cancer

Circulating tumor cells (CTCs) are particularly rare in non-metastatic breast cancer, and the clinical validity of CTC detection in that clinical setting was initially not well recognized. A cytological CTC detection device (CellSearch) fulfilling the CLIA requirements for analytical validity was subsequently developed and, in 2008, we reported the first study (REMAGUS02) showing that distant metastasis-free survival was shorter in early breast cancer patients with one or more CTCs. In the past 10 years, other clinical studies and meta-analyses have established CTC detection as a level-of-evidence 1 prognostic biomarker for local relapses, distant relapses, and overall survival. This review summarizes available data on CTC detection and the promises of this proliferation- and subtype-independent metastasis-associated biomarker in early breast cancer patients.

Abstract 4599: Detecting MSI phenotype in circulating blood DNA

Background: Microsatellite instability (MSI) is a hypermutator phenotype occurring in gastrointestinal, endometrial and colorectal tumors, and more rarely, in urinary tract, ovarian, breast, prostate, lung, head and neck, liver and glioblastoma tumors. The diagnosis of MSI phenotype has recently emerged as the first pan-tumor biomarker likely to predict clinical benefit from immune-checkpoint blockade therapy, making its precise identification primordial for treatment decisions and disease monitoring. Current diagnosis of MSI is performed by multiplex PCR of five microsatellite markers, followed by capillary electrophoresis to detect shifts in allele size. An important limitation of this method is its low sensitivity preventing its use when tumor content is below 10%.

Methods: We designed ddPCR assays examining 3 microsatellites. Analytical performance was assessed in vitro. Clinical performance was evaluated in a series of FFPE and body fluid DNA samples obtained from patients with Stage IV colorectal or endometrial carcinomas, previously classified as MSI-H or MSS using the standard pentaplex PCR method. Mutant allele frequencies (MAF) quantified with the ddPCR MSI assay were also compared with the MAFs reported by ddPCR assays targeting specific BRAF or PIK3CA mutations.

Results: The ddPCR assays for the 3 microsatellites were found to have high specificity and reached a limit of detection of &lt;0.1%. A perfect concordance with the MSI status determined by the pentaplex assay was observed in the 50 tumor samples tested (25 MSI-H and 25 MSS). Importantly, the ddPCR assays diagnosed the MSI phenotype in the plasma of all patients with MSI-H tumors, without false positives in MSS cases. Furthermore, an excellent correlation was observed in the 6 FFPE (R2:0.81) and 8 body fluid (R2:0.99) MSI-H samples were the MAFs measured by our assay could be compared with the ones obtained by ddPCR assays targeting specific mutations in BRAF or PIK3CA genes.

Conclusion: This technique allows a cost-effective, sensitive and large scale screening of the MSI phenotype, as well as the follow-up of MSI patients using liquid biopsies.

Citation Format: Marc-Henri Stern, Amanda B. Silveira, Ivan Bieche, Samia Melaabi, Luc Cabel, Bruno Buecher, Jean-Yves Pierga, Francois-Clement Bidard, Charlotte Proudhon. Detecting MSI phenotype in circulating blood DNA [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4599.

Abstract 3867: Activating ESR1 mutations detection by single ddPCR assay

Background: In metastatic breast cancer, most mutations of ESR1 (which encodes the estrogen receptor alpha ERα) occur in exon 5 (E380Q) and/or 8 (L536, Y537, D538). These mutations are responsible for acquired resistance to hormone deprivation but can be targeted by selective estrogen receptor degraders (SERD) such as fulvestrant. Circulating tumor DNA (ctDNA) allows a non-invasive assessment of ESR1 mutations, but implementing its routine use requires a sensitive, specific and fast technique, at a moderate cost.

Methods: We designed a ddPCR assay scanning for all mutations targeting the 536-538 amino acid residues of ERα with a unique pair of probes and multiplexed it with other probes targeting E380Q. Sensitivity and specificity were assessed in vitro; this multiple hotspot scanning (MHS) ddPCR was used to detect ESR1 mutants in cohorts of patients with hormone deprivation-resistant metastatic breast cancer.

Results: All the above-mentioned mutations were detected in a single MHS ddPCR assay with a high specificity and with a limit of detection of ~0.1% in mutant allele frequency, allowing ESR1 mutant detection in circulating tumor DNA. A perfect concordance with targeted next generation sequencing was observed in the first 31 clinical plasma samples tested. This technique also detected ESR1 polyclonal mutations.

Conclusion: This technique allows for a sensitive, large scale and repeated screening of ESR1 mutants with a single ddPCR assay. The clinical utility of ESR1 mutation detection by this technique is now investigated in the randomized phase 3 PADA-1 trial (sponsors: Unicancer/Gineco), in which patients with rising levels of circulating ESR1 mutants during aromatase inhibitor / palbociclib therapy are eventually switched to fulvestrant / palbociclib (NCT03079011).

ESR1 mutants detectable in a single ddPCR assayAA changesMutant frequency (as per Toy et al, Cancer Discov 2017).E380Q19%L536H4%L536P2%L536R1%Y537S11%Y537C6%Y537N5%Y537D1%D538G32%D538-L539ins1%total % of mutations covered~82% (Many of the 18% remaining mutations occur outside exon 5 & 8 and have no proven functional impact)

Citation Format: Francois-Clement Bidard, Emmanuelle Jeannot, Luc Cabel, Nicolas Epaillard, Radouane El Ayachy, Aurelien Noret, Anne Vincent-Salomon, Jean-Yves Pierga, Ivan Bieche, Charlotte Proudhon, Marc-Henri Stern. Activating ESR1 mutations detection by single ddPCR assay [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3867.

Cdk4/6 inhibitors and overall survival: power of first-line trials in metastatic breast cancer

Palbociclib, ribociclib, and abemaciclib have been investigated in combination with aromatase inhibitors as first-line therapy for metastatic hormone receptor-positive breast cancer (PALOMA-2, MONALEESA-2 and MONALEESA-7, MONARCH-3 trials, respectively); pivotal trials led to absolute median progression-free survival (PFS) gain of about 15 months. We aimed to estimate, for each trial, the statistical power to demonstrate a significant gain in overall survival (OS). Power was calculated with Freedman's formula. Given the allocation ratio and the number of events, power was computed as a function of hazard ratio. We focused on four specific hazard ratio values (0.94, 0.89, 0.81, and 0.77), which are estimated to correspond to absolute 3, 6, 12, and 15 months gain in OS, respectively. For these calculations, the type I error rate was stated at 5% with a two-sided test, and we assumed that the risk of death was constant over time. PALOMA-2 and MONALEESA trials have an almost similar power despite different allocation ratios, while MONARCH-3 has a more limited power. Overall, the power of the four trials to demonstrate a statistically significant improvement in OS is less than 70% if the prolongation in median OS is ≤12 months, whatever the OS data maturity. This analysis shows that OS results are jeopardized by limited powers, and a meta-analysis might be required to demonstrate OS benefit. Conversely, if a significant OS improvement is observed in some but not at all trials, this discrepancy might be more attributable to chance than to a truly different drug efficacy.

A randomized multicenter phase 3 trial of adjuvant fotemustine versus surveillance in high risk uveal melanoma (UM) patients (FOTEADJ)

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Background: Up to 30% of UM patients will develop metastases, with a median survival of 12 months in the metastating setting. Prognostic factors combine clinical features of the primary tumor (diameter, thickness, retinal detachment, extra-scleral extension) and genetic factors (monosomy 3, 8 q gain and class 1 /2 gene expression profiling).The genomic analysis is feasible by fine needle aspiration biopsies before radiotherapy for small UM or on enucleated eyes. Methods: Multicenter randomized phase 3 trial with adjuvant fotemustine, 6 cycles, 100 mg/m2 versus surveillance for 3 years (liver tests/3 months, liver MRI or CT/6 months, whole body CT/12 months) in patients with high risk of recurrence, defined by clinical criteria (diameter > 15 mm with extra scleral extension and/or retinal detachment or diameter > 18 mm) or genomic high risk signature by array-CGH (monosomy 3 or deletion of 3p associated with gain of chromosome 8). The primary objective was 5-year Metastasis Free Survival (MFS). With an expected increase of 5-year MFS from 50 to 70%, 302 patients and 99 events were required to achieve an 95%-power with a 5% type I error rate. Secondary objectives were overall survival (OS), safety (NCI-CTC v3), quality of life (QLQ-C30). Interim analyses were planned for safety and after 50 events, disclosed to an independent safety monitoring board. Results: The trial was stopped for futility after 244 patients had been recruited between June 2009 and January 2016. No unexpected toxicity was found in the chemotherapy group. The study was amended to go on with intensive surveillance in new high risk patients. Ninety-one metastases and 43 deaths were reported, with no treatment-related death. With a median follow-up of 3 years, the 3-year MFS is 60.3% in the chemo group and 60.7% in the surveillance group (HR 0.97 [0.64-1.47]). The 3-year OS is 79.4% [73.2-85.7], with no difference between the 2 groups of patients. Conclusions: FOTEADJ is the first adjuvant randomized phase 3 trial based on genomic analysis in high risk UM patients. Despite negative results, it shows the feasibility of multicenter adjuvant studies in this rare cancer and provides genomic data in small tumors for future trials. Clinical trial information: NCT02843386.

Genetic Heterogeneity in Therapy-Naïve Synchronous Primary Breast Cancers and Their Metastases

Purpose: Paired primary breast cancers and metachronous metastases after adjuvant treatment are reported to differ in their clonal composition and genetic alterations, but it is unclear whether these differences stem from the selective pressures of the metastatic process, the systemic therapies, or both. We sought to define the repertoire of genetic alterations in breast cancer patients with de novo metastatic disease who had not received local or systemic therapy.Experimental Design: Up to two anatomically distinct core biopsies of primary breast cancers and synchronous distant metastases from nine patients who presented with metastatic disease were subjected to high-depth whole-exome sequencing. Mutations, copy number alterations and their cancer cell fractions, and mutation signatures were defined using state-of-the-art bioinformatics methods. All mutations identified were validated with orthogonal methods.Results: Genomic differences were observed between primary and metastatic deposits, with a median of 60% (range 6%-95%) of shared somatic mutations. Although mutations in known driver genes including TP53, PIK3CA, and GATA3 were preferentially clonal in both sites, primary breast cancers and their synchronous metastases displayed spatial intratumor heterogeneity. Likely pathogenic mutations affecting epithelial-to-mesenchymal transition-related genes, including SMAD4, TCF7L2, and TCF4 (ITF2), were found to be restricted to or enriched in the metastatic lesions. Mutational signatures of trunk mutations differed from those of mutations enriched in the primary tumor or the metastasis in six cases.Conclusions: Synchronous primary breast cancers and metastases differ in their repertoire of somatic genetic alterations even in the absence of systemic therapy. Mutational signature shifts might contribute to spatial intratumor genetic heterogeneity. Clin Cancer Res; 23(15); 4402-15. ©2017 AACR.

Patient-Specific Circulating Tumor DNA Detection during Neoadjuvant Chemotherapy in Triple-Negative Breast Cancer

BACKGROUND

In nonmetastatic triple-negative breast cancer (TNBC) patients, we investigated whether circulating tumor DNA (ctDNA) detection can reflect the tumor response to neoadjuvant chemotherapy (NCT) and detect minimal residual disease after surgery.

METHODS

Ten milliliters of plasma were collected at 4 time points: before NCT; after 1 cycle; before surgery; after surgery. Customized droplet digital PCR (ddPCR) assays were used to track tumor protein p53 (TP53) mutations previously characterized in tumor tissue by massively parallel sequencing (MPS).

RESULTS

Forty-six patients with nonmetastatic TNBC were enrolled. TP53 mutations were identified in 40 of them. Customized ddPCR probes were validated for 38 patients, with excellent correlation with MPS (r = 0.99), specificity (≥2 droplets/assay), and sensitivity (at least 0.1%). At baseline, ctDNA was detected in 27/36 patients (75%). Its detection was associated with mitotic index (P = 0.003), tumor grade (P = 0.003), and stage (P = 0.03). During treatment, we observed a drop of ctDNA levels in all patients but 1. No patient had detectable ctDNA after surgery. The patient with rising ctDNA levels experienced tumor progression during NCT. Pathological complete response (16/38 patients) was not correlated with ctDNA detection at any time point. ctDNA positivity after 1 cycle of NCT was correlated with shorter disease-free (P &lt; 0.001) and overall (P = 0.006) survival.

CONCLUSIONS

Customized ctDNA detection by ddPCR achieved a 75% detection rate at baseline. During NCT, ctDNA levels decreased quickly and minimal residual disease was not detected after surgery. However, a slow decrease of ctDNA level during NCT was strongly associated with shorter survival.