TROPION-Breast03: a randomized phase III global trial of datopotamab deruxtecan ± durvalumab in patients with triple-negative breast cancer and residual invasive disease at surgical resection after neoadjuvant therapy

Background

Despite advances in the treatment of early triple-negative breast cancer (TNBC), patients with residual invasive disease after neoadjuvant therapy have a high risk of disease recurrence and worse survival outcomes than those who have pathological complete response (pCR). Improving outcomes in early TNBC remains an unmet need requiring new adjuvant treatment approaches. Datopotamab deruxtecan (Dato-DXd) is an antibody-drug conjugate comprising a humanized anti-trophoblast cell-surface antigen 2 immunoglobulin G1 (IgG1) monoclonal antibody attached via a plasma-stable, cleavable linker to a potent topoisomerase I inhibitor payload, with activity observed in advanced TNBC.

Objectives

TROPION-Breast03 is an ongoing phase III study evaluating the efficacy and safety of Dato-DXd alone or combined with durvalumab versus standard-of-care therapy as adjuvant treatment in patients with stage I-III TNBC with residual invasive disease at surgical resection following neoadjuvant treatment.

Methods and design

Eligible patients, aged ⩾18 years, will be randomized in a 2:1:2 ratio to receive Dato-DXd [6 mg/kg intravenously (IV) every 3 weeks (Q3W); eight cycles] and durvalumab (1120 mg IV Q3W; nine cycles), Dato-DXd monotherapy (6 mg/kg IV Q3W), or investigator's choice of therapy (ICT; capecitabine, pembrolizumab, or capecitabine and pembrolizumab). The primary endpoint is invasive disease-free survival (iDFS) for Dato-DXd and durvalumab versus ICT. Key secondary endpoints include safety, distant disease-free survival, and overall survival for Dato-DXd and durvalumab versus ICT and iDFS for Dato-DXd monotherapy versus ICT.

Ethics

TROPION-Breast03 will be approved by the independent ethics committees or institutional review boards at each study site. All study participants will provide written informed consent.

Discussion

TROPION-Breast03 will help define the potential role of Dato-DXd in the treatment of patients with early-stage TNBC who do not have pCR after neoadjuvant therapy.

Trial registration

ClinicalTrials.gov identifier: NCT05629585 (registration date: 29 November 2022).

Subgroup analyses from the phase 3 ASCENT study of sacituzumab govitecan in metastatic triple-negative breast cancer

In this post hoc analysis of the ASCENT study, we compared outcomes with sacituzumab govitecan (SG) vs single-agent chemotherapy in clinically important subgroups of patients with metastatic triple-negative breast cancer (mTNBC). Patients with mTNBC refractory to/relapsing after ≥2 prior chemotherapies (≥1 in the metastatic setting) were randomized 1:1 to receive SG or treatment of physician's choice (TPC) until unacceptable toxicity/progression. The primary endpoint was progression-free survival (PFS) per RECIST 1.1 by central review in patients without brain metastases. Patients with brain metastases were allowed if metastases were stable ≥4 weeks. In the intention-to-treat (ITT) population, 19% of patients were age ≥65 years; 12% were Black, and 12% had brain metastases. SG improved PFS and overall survival (OS), respectively, vs TPC in patients age ≥65 years (7.1 vs 2.4 months and 14.7 vs 8.9 months), or of Black race (5.4 vs 2.2 months and 13.8 vs 8.5 months), consistent with outcomes in the ITT population. Patients with brain metastases had numerically higher median PFS with SG vs TPC, but median OS was similar between treatment groups. SG was well tolerated and had a manageable safety profile consistent with the full safety population across all subgroups; neutropenia and diarrhea were the most common treatment-emergent adverse events. These findings confirm the meaningful clinical benefit of SG vs standard chemotherapy in patient subgroups with high unmet needs. SG should be considered an effective and safe treatment option for patients with mTNBC eligible for second-line or later therapy. ClinicalTrials.gov Number: NCT02574455.

Pharmacological suppression of the OTUD4/CD73 proteolytic axis revives antitumor immunity against immune-suppressive breast cancers

Despite widespread utilization of immunotherapy, treating immune-cold tumors remains a challenge. Multiomic analyses and experimental validation identified the OTUD4/CD73 proteolytic axis as a promising target in treating immune-suppressive triple negative breast cancer (TNBC). Mechanistically, deubiquitylation of CD73 by OTUD4 counteracted its ubiquitylation by TRIM21, resulting in CD73 stabilization inhibiting tumor immune responses. We further demonstrated the importance of TGF-β signaling for orchestrating the OTUD4/CD73 proteolytic axis within tumor cells. Spatial transcriptomics profiling discovered spatially resolved features of interacting malignant and immune cells pertaining to expression levels of OTUD4 and CD73. In addition, ST80, a newly developed inhibitor, specifically disrupted proteolytic interaction between CD73 and OTUD4, leading to reinvigoration of cytotoxic CD8+ T cell activities. In preclinical models of TNBC, ST80 treatment sensitized refractory tumors to anti-PD-L1 therapy. Collectively, our findings uncover what we believe to be a novel strategy for targeting the immunosuppressive OTUD4/CD73 proteolytic axis in treating immune-suppressive breast cancers with the inhibitor ST80.

The Right Dose: Results of a Patient Advocate-Led Survey of Individuals With Metastatic Breast Cancer Regarding Treatment-Related Side Effects and Views About Dosage Assessment to Optimize Quality of Life

PURPOSE

Although patients with metastatic breast cancer (MBC) have been living longer with the advent of more effective treatments such as targeted therapy and immunotherapy, the disease remains incurable, and most patients will undergo therapy indefinitely. When beginning therapy, patients are typically prescribed dose often based upon the maximum tolerated dose identified in phase I clinical trials. However, patients' perspectives about tolerability and willingness to discuss individualized dosing of drugs upon initiation of a new regimen and throughout the course of treatment have not been comprehensively evaluated.

METHODS

Patient advocates and medical oncologists from the Patient-Centered Dosing Initiative (PCDI) developed a survey to ascertain the prevalence and severity of MBC patients' treatment-related side effects, the level of patient-physician communication, mitigation strategies, perception about the relative efficacy of higher versus lower doses, and willingness to discuss alternative dosing. The PCDI distributed the anonymous confidential online survey in August 2020 to individuals with self-reported MBC.

RESULTS

One thousand and two hundred twenty-one patients with MBC completed the survey. 86.1% (n = 1,051) reported experiencing at least one significant treatment-related side effect, and of these, 20.3% (n = 213) visited the emergency room/hospital and 43.2% (n = 454) missed at least one treatment. Nearly all patients with side effects (97.6%, n = 1,026) informed their doctor and 81.7% (n = 838) received assistance. Of the 556 patients given a dose reduction for side-effect mitigation, 82.6% (n = 459) reported relief. Notably, majority of patients (53.3%, n = 651) do not believe that higher dose is always more effective than lower dose, and 92.3% (n = 1,127) would be willing to discuss flexible dosing options with their physicians based upon personal characteristics to optimize quality of life.

CONCLUSION

Given that the majority of patients with MBC experienced at least one substantial treatment-related side effect and most patients given a dose reduction reported improvement, innovative dosage-related strategies are warranted to sustain and improve patients' well-being. Patient-physician discussions in which the patient's unique attributes and circumstances are assessed upon initiation of new treatment and throughout the course of therapy may facilitate the identification of the most favorable dose for each patient, and the majority of patients would be receptive to this approach.

TROPION-Breast01: Datopotamab deruxtecan vs chemotherapy in pre-treated inoperable or metastatic HR+/HER2- breast cancer

Improving the prognosis for patients with metastatic HR+/HER2- breast cancer remains an unmet need. Patients with tumors that have progressed on endocrine therapy and/or are not eligible for endocrine therapy had limited treatment options beyond chemotherapy. Antibody-drug conjugates are a novel and promising treatment class in this setting. Datopotamab deruxtecan (Dato-DXd) consists of a TROP2-directed humanized IgG1 monoclonal antibody attached via a serum-stable cleavable linker to a topoisomerase I inhibitor payload. TROPION-Breast01 is an ongoing phase III study that is evaluating the efficacy and safety of Dato-DXd compared with investigator's choice of standard-of-care chemotherapy in patients with inoperable or metastatic HR+/HER2- breast cancer who have received one or two prior lines of systemic chemotherapy in the inoperable or metastatic setting. Clinical Trial Registration: NCT05104866 (ClinicalTrials.gov).

Final Results From the Randomized Phase III ASCENT Clinical Trial in Metastatic Triple-Negative Breast Cancer and Association of Outcomes by Human Epidermal Growth Factor Receptor 2 and Trophoblast Cell Surface Antigen 2 Expression

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported.Sacituzumab govitecan (SG), a first-in-class anti-trophoblast cell surface antigen 2 (Trop-2) antibody-drug conjugate, demonstrated superior efficacy over single-agent chemotherapy (treatment of physician's choice [TPC]) in patients with metastatic triple-negative breast cancer (mTNBC) in the international, multicenter, phase III ASCENT study.Patients were randomly assigned 1:1 to receive SG or TPC until unacceptable toxicity/progression. Final efficacy secondary end point analyses and post hoc analyses of outcomes stratified by Trop-2 expression and human epidermal growth factor receptor 2 status are reported. Updated safety analyses are provided.In this final analysis, SG (n = 267) improved median progression-free survival (PFS; 4.8 v 1.7 months; hazard ratio (HR), 0.41 [95% CI, 0.33 to 0.52]) and median overall survival (OS; 11.8 v 6.9 months; HR, 0.51 [95% CI, 0.42 to 0.63]) over TPC (n = 262). SG improved PFS over TPC in each Trop-2 expression quartile (n = 168); a trend was observed for improved OS across quartiles. Overall, SG had a manageable safety profile, with ≤5% of treatment-related discontinuations because of adverse events and no treatment-related deaths. The safety profile was consistent across all subgroups.These data confirm the clinical benefit of SG over chemotherapy, reinforcing SG as an effective treatment option in patients with mTNBC in the second line or later.

Randomized adaptive selection trial of cryotherapy, compression therapy, and placebo to prevent taxane-induced peripheral neuropathy in patients with breast cancer

BACKGROUND

Chemotherapy-induced peripheral neuropathy (CIPN) is a common and debilitating adverse effect of taxane therapy. Small non-randomized studies in patients with early-stage breast cancer (ESBC) suggest both cryotherapy and compression therapy may prevent CIPN. It is unknown which is more effective.

METHODS

We conducted a randomized phase IIB adaptive sequential selection trial of cryotherapy vs. compression therapy vs. placebo ("loose" gloves/socks) during taxane chemotherapy. Participants were randomized in triplets. Garments were worn for 90-120 min, beginning 15 min prior and continuing for 15 min following the infusion. The primary goal was to select the best intervention based on a Levin-Robbins-Leu sequential selection procedure. The primary endpoint was a < 5-point decrease in the Functional Assessment of Cancer Therapy Neurotoxicity (FACT-NTX) at 12 weeks. An arm was eliminated if it had four or more fewer successes than the currently leading arm. Secondary endpoints included intervention adherence and patient-reported comfort/satisfaction.

RESULTS

Between April 2019 and April 2021, 63 patients were randomized (cryotherapy (20); compression (22); placebo (21)). Most patients (60.3%) were treated with docetaxel. The stopping criterion was met after the 17th triplet (n = 51) was evaluated; success at 12 weeks occurred in 11 (64.7%) on compression therapy, 7 (41.1%) on cryotherapy, and 7 (41.1%) on placebo. Adherence to the intervention was lowest with cryotherapy (35.0%) compared to compression (72.7%) and placebo (76.2%).

CONCLUSION

Compression therapy was the most effective intervention in this phase IIB selection trial to prevent CIPN and was well tolerated. Compression therapy for the prevention of CIPN should be evaluated in a phase III study.

CLINICAL TRIAL REGISTRATION

ClinicaTrials.gov Identifier: NCT03873272.

The HER2-directed antibody-drug conjugate DHES0815A in advanced and/or metastatic breast cancer: preclinical characterization and phase 1 trial results

Approved antibody-drug conjugates (ADCs) for HER2-positive breast cancer include trastuzumab emtansine and trastuzumab deruxtecan. To develop a differentiated HER2 ADC, we chose an antibody that does not compete with trastuzumab or pertuzumab for binding, conjugated to a reduced potency PBD (pyrrolobenzodiazepine) dimer payload. PBDs are potent cytotoxic agents that alkylate and cross-link DNA. In our study, the PBD dimer is modified to alkylate, but not cross-link DNA. This HER2 ADC, DHES0815A, demonstrates in vivo efficacy in models of HER2-positive and HER2-low cancers and is well-tolerated in cynomolgus monkey safety studies. Mechanisms of action include induction of DNA damage and apoptosis, activity in non-dividing cells, and bystander activity. A dose-escalation study (ClinicalTrials.gov: NCT03451162) in patients with HER2-positive metastatic breast cancer, with the primary objective of evaluating the safety and tolerability of DHES0815A and secondary objectives of characterizing the pharmacokinetics, objective response rate, duration of response, and formation of anti-DHES0815A antibodies, is reported herein. Despite early signs of anti-tumor activity, patients at higher doses develop persistent, non-resolvable dermal, ocular, and pulmonary toxicities, which led to early termination of the phase 1 trial.

CDK4/6 Inhibition in the Metastatic Setting: Where Are We Headed?

OPINION STATEMENT

Hormone receptor positive (HR+), human epidermal growth factor receptor 2 negative (HER-2-) metastatic breast cancer (MBC) is the most common subtype of breast cancer. Due to therapeutic advances with molecularly targeted therapies, the prognosis for patients with metastatic disease has improved significantly. The advent of CDK4/6 inhibitors (CDK4/6i) has changed the treatment paradigm for patients with HR+HER2-MBC. CDK4/6i allowed for marked improvement in overall survival, delaying the time to chemotherapy initiation, and improved quality of life for our patients. Efforts are now focused on the best approach(es) for patients after progression on CDK4/6i. Can we further harness the benefit of CDK4/6i in novel combinations at the time of progression? Should we continue CDK4/6i or proceed other novel agents or endocrine therapies? As we advance our treatment strategies for HR+HER2-MBC, there is no longer a one-size-fits-all model, but instead a multifaceted and personalized approach lending to improved outcomes for our patients.

Randomized Phase II Trial of Endocrine Therapy With or Without Ribociclib After Progression on Cyclin-Dependent Kinase 4/6 Inhibition in Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Negative Metastatic Breast Cancer: MAINTAIN Trial

PURPOSE

Cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) with endocrine therapy (ET) improves progression-free survival (PFS) and overall survival (OS) in hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer (MBC). Although preclinical and clinical data demonstrate a benefit in changing ET and continuing a CDK4/6i at progression, no randomized prospective trials have evaluated this approach.

METHODS

In this investigator-initiated, phase II, double-blind placebo-controlled trial in patients with HR+/HER2- MBC whose cancer progressed during ET and CDK4/6i, participants switched ET (fulvestrant or exemestane) from ET used pre-random assignment and randomly assigned 1:1 to the CDK4/6i ribociclib versus placebo. PFS was the primary end point, defined as time from random assignment to disease progression or death. Assuming a median PFS of 3.8 months with placebo, we had 80% power to detect a hazard ratio (HR) of 0.58 (corresponding to a median PFS of at least 6.5 months with ribociclib) with 120 patients randomly assigned using a one-sided log-rank test and significance level set at 2.5%.

RESULTS

Of the 119 randomly assigned participants, 103 (86.5%) previously received palbociclib and 14 participants received ribociclib (11.7%). There was a statistically significant PFS improvement for patients randomly assigned to switched ET plus ribociclib (median, 5.29 months; 95% CI, 3.02 to 8.12 months) versus switched ET plus placebo (median, 2.76 months; 95% CI, 2.66 to 3.25 months) HR, 0.57 (95% CI, 0.39 to 0.85); P = .006. At 6 and 12 months, the PFS rate was 41.2% and 24.6% with ribociclib, respectively, compared with 23.9% and 7.4% with placebo.

CONCLUSION

In this randomized trial, there was a significant PFS benefit for patients with HR+/HER2- MBC who switched ET and received ribociclib compared with placebo after previous CDK4/6i and different ET.

Radiotherapy Use and Incidence of Locoregional Recurrence in Patients With Favorable-Risk, Node-Positive Breast Cancer Enrolled in the SWOG S1007 Trial

Importance

Little is known about regional nodal irradiation (RNI) practice patterns or rates of locoregional recurrence (LRR) with and without RNI in patients with limited nodal disease and favorable biology treated with modern surgical and systemic therapy, including approaches that de-escalate those latter treatments.

Objective

To investigate how often patients with low-recurrence score breast cancer with 1 to 3 nodes involved receive RNI, incidence and predictors of LRR, and associations between locoregional therapy and disease-free survival.

Design, Setting, and Participants

In this secondary analysis of the SWOG S1007 trial, patients with hormone receptor-positive, ERBB2-negative breast cancer, and a Oncotype DX 21-gene Breast Recurrence Score assay result of no more than 25, were randomized to endocrine therapy alone vs chemotherapy then endocrine therapy. Prospectively collected radiotherapy information was collected from 4871 patients treated in diverse settings. Data were analyzed June 2022 to April 2023.

Exposure

Receipt of RNI (targeting at least the supraclavicular region).

Main Outcome(s) and Measure(s)

Cumulative incidence of LRR was calculated by locoregional treatment received. Analyses were assessed for associations between invasive disease-free survival (IDFS) and locoregional therapy, adjusted for menopausal status, treatment group, recurrence score, tumor size, nodes involved, and axillary surgery. Radiotherapy information was recorded in the first year after randomization, so survival analyses were landmarked as starting at 1 year among those still at risk.

Results

Of 4871 female patients (median [range] age, 57 [18-87] years) with radiotherapy forms, 3947 (81.0%) reported radiotherapy receipt. Of 3852 patients who received radiotherapy and had complete information on targets, 2274 (59.0%) received RNI. With a median follow-up of 6.1 years, the cumulative incidence of LRR by 5 years was 0.85% among patients who received breast-conserving surgery and radiotherapy with RNI; 0.55% after breast-conserving surgery with radiotherapy without RNI; 0.11% after mastectomy with postmastectomy radiotherapy; and 1.7% after mastectomy without radiotherapy. Similarly low LRR was observed within the group assigned to endocrine therapy without chemotherapy. The rate of IDFS did not differ by RNI receipt (premenopausal: hazard ratio [HR], 1.03; 95% CI, 0.74-1.43; P = .87; postmenopausal: HR, 0.85; 95% CI, 0.68-1.07; P = .16).

Conclusions and Relevance

In this secondary analysis of a clinical trial, RNI use was divided in the setting of biologically favorable N1 disease, and rates of LRR were low even in patients who did not receive RNI. Disease-free survival was not associated with RNI receipt; omission of chemotherapy among patients similar to those enrolled in the S1007 trial is not an independent indication for use of RNI.

The role of immune checkpoint inhibition in triple negative breast cancer

INTRODUCTION

Immunotherapy has revolutionized cancer treatment, including TNBC, which has limited options of treatment and poor prognosis. ICIs studied in TNBC include pembrolizumab, nivolumab, atezolizumab, and durvalumab. Initial studies exploring ICI monotherapy demonstrated promising yet limited responses. Subsequent studies, KEYNOTE 522 and KEYNOTE 355, which combined ICI with chemotherapy, have resulted in the FDA approval of pembrolizumab in the early-stage and metastatic setting, respectively.

AREAS COVERED

This article provides a comprehensive review of the role of ICI in the treatment of TNBC. We reviewed the trials that have evaluated ICI monotherapy, dual therapy, ICI in combination with chemotherapy, targeted therapy, vaccines and radiation. Additionally, we reviewed potential biomarkers of response and immune-related adverse events (irAEs). A literature search was conducted via PubMed and ClinicalTrials.gov as of 5 June 2023.

EXPERT OPINION

Various approaches combining immunotherapy with chemotherapy, targeted therapy, vaccines and radiation have been assessed. Pembrolizumab remains the only ICI approved in both the early stage and mTNBC. The role of adjuvant pembrolizumab in those who achieved pCR after neoadjuvant therapy is being investigated. Combining ICI with PARP inhibitors and radiation shows promise. More research is needed in identifying predictors of response. Monitoring of irAEs remains crucial.

Treatment patterns and outcomes associated with sequential and non-sequential use of CDK4 & 6 inhibitors in patients with HR+, HER2- MBC in the real world

PURPOSE

Cyclin Dependent Kinase 4 & 6 inhibitors (CDK4 & 6i) have transformed the management of HR+, HER2- metastatic breast cancer (MBC); however, the optimal sequence of these treatments and other systemic therapies for MBC remains unclear.

METHODS

This study analyzed electronic medical records from the ConcertAI Oncology Dataset. US patients who received abemaciclib and at least one other systemic line of therapy (LOT) for HR+, HER2- MBC were eligible. Treatment sequences were grouped, and data for two pairs of groups are presented herein (N = 397): Group 1 (1L CDK4 & 6i to 2L CDK4 & 6i) vs. Group 2 (1L CDK4 & 6i to 2L non-CDK4 & 6i), and Group 3 (2L CDK4 & 6i to 3L CDK4 & 6i) vs. Group 4 (2L CDK4 & 6i to 3L non-CDK4 & 6i). Time-to-event outcomes (PFS and PFS-2) were analyzed using Kaplan-Meier method and Cox proportional hazard regression.

RESULTS

In the total cohort of 690 patients, the most prevalent sequence was 1L CDK4 & 6i to 2L CDK4 & 6i (n = 165). For the 397 patients across Groups 1-4, sequential CDK4 & 6i demonstrated numerically longer PFS and PFS-2 versus non-sequential CDK4 & 6i. Adjusted results demonstrate that patients in Group 1 demonstrated significantly longer PFS (p = 0.05) versus Group 2.

CONCLUSIONS

Although retrospective and hypothesis-generating, these data demonstrate numerically longer outcomes in the subsequent LOT associated with sequential CDK4 & 6i treatment.

A Transcriptome-Based Precision Oncology Platform for Patient-Therapy Alignment in a Diverse Set of Treatment-Resistant Malignancies

Predicting in vivo response to antineoplastics remains an elusive challenge. We performed a first-of-kind evaluation of two transcriptome-based precision cancer medicine methodologies to predict tumor sensitivity to a comprehensive repertoire of clinically relevant oncology drugs, whose mechanism of action we experimentally assessed in cognate cell lines. We enrolled patients with histologically distinct, poor-prognosis malignancies who had progressed on multiple therapies, and developed low-passage, patient-derived xenograft models that were used to validate 35 patient-specific drug predictions. Both OncoTarget, which identifies high-affinity inhibitors of individual master regulator (MR) proteins, and OncoTreat, which identifies drugs that invert the transcriptional activity of hyperconnected MR modules, produced highly significant 30-day disease control rates (68% and 91%, respectively). Moreover, of 18 OncoTreat-predicted drugs, 15 induced the predicted MR-module activity inversion in vivo. Predicted drugs significantly outperformed antineoplastic drugs selected as unpredicted controls, suggesting these methods may substantively complement existing precision cancer medicine approaches, as also illustrated by a case study.

SIGNIFICANCE

Complementary precision cancer medicine paradigms are needed to broaden the clinical benefit realized through genetic profiling and immunotherapy. In this first-in-class application, we introduce two transcriptome-based tumor-agnostic systems biology tools to predict drug response in vivo. OncoTarget and OncoTreat are scalable for the design of basket and umbrella clinical trials. This article is highlighted in the In This Issue feature, p. 1275.

A Gene Panel Associated With Abemaciclib Utility in ESR1-Mutated Breast Cancer After Prior Cyclin-Dependent Kinase 4/6-Inhibitor Progression

PURPOSE

For patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer (MBC), first-line treatment is endocrine therapy (ET) plus cyclin-dependent kinase 4/6 inhibition (CDK4/6i). After disease progression, which often comes with ESR1 resistance mutations (ESR1-MUT), which therapies to use next and for which patients are open questions. An active area of exploration is treatment with further CDK4/6i, particularly abemaciclib, which has distinct pharmacokinetic and pharmacodynamic properties compared with the other approved CDK4/6 inhibitors, palbociclib and ribociclib. We investigated a gene panel to prognosticate abemaciclib susceptibility in patients with ESR1-MUT MBC after palbociclib progression.

METHODS

We examined a multicenter retrospective cohort of patients with ESR1-MUT MBC who received abemaciclib after disease progression on ET plus palbociclib. We generated a panel of CDK4/6i resistance genes and compared abemaciclib progression-free survival (PFS) in patients without versus with mutations in this panel (CDKi-R[-] v CDKi-R[+]). We studied how ESR1-MUT and CDKi-R mutations affect abemaciclib sensitivity of immortalized breast cancer cells and patient-derived circulating tumor cell lines in culture.

RESULTS

In ESR1-MUT MBC with disease progression on ET plus palbociclib, the median PFS was 7.0 months for CDKi-R(-) (n = 17) versus 3.5 months for CDKi-R(+) (n = 11), with a hazard ratio of 2.8 (P = .03). In vitro, CDKi-R alterations but not ESR1-MUT induced abemaciclib resistance in immortalized breast cancer cells and were associated with resistance in circulating tumor cells.

CONCLUSION

For ESR1-MUT MBC with resistance to ET and palbociclib, PFS on abemaciclib is longer for patients with CDKi-R(-) than CDKi-R(+). Although a small and retrospective data set, this is the first demonstration of a genomic panel associated with abemaciclib sensitivity in the postpalbociclib setting. Future directions include testing and improving this panel in additional data sets, to guide therapy selection for patients with HR+/HER2- MBC.

A Discordant Pattern of Uptake on 68 Ga-PSMA PET/CT Versus 18 F-Fluciclovine PET/CT in Radiation-Induced Hepatitis : Implications for Early Postradiotherapy Imaging-Based Response Assessment

ABSTRACT

A 62-year-old woman with right-sided invasive lobular breast carcinoma completed external beam radiotherapy 6 weeks before undergoing a 68 Ga-PSMA PET/CT and 18 F-fluciclovine PET/CT scan as part of an ongoing clinical trial (NCT04750473) assessing the performance of these molecular imaging modalities in invasive lobular breast carcinoma. The 68 Ga-PSMA PET/CT demonstrated a band-like area of increased radiotracer uptake in the dome of the right lobe of the liver anteriorly, whereas 18 F-fluciclovine PET/CT done a day later revealed photopenia in the corresponding area of the liver. The external beam radiotherapy plan confirmed that the radiotherapy field overlaid the region of the hepatic discordant radiotracer uptake on the PET/CT scans.

Abstract PD11-01: PD11-01 Evaluation of the PD-1 Inhibitor Cemiplimab in early-stage, high-risk HER2-negative breast cancer: Results from the neoadjuvant I-SPY 2 TRIAL

Background: I-SPY2 is a multicenter, phase 2 trial using response-adaptive randomization within biomarker subtypes defined by hormone-receptor (HR), HER2, and MammaPrint (MP) status to evaluate novel agents as neoadjuvant therapy for high-risk breast cancer. The primary endpoint is pathologic complete response (pCR). Cemiplimab (Cemi) is a PD-1 inhibitor approved for the treatment of NSCLC, cutaneous basal, and squamous cell cancer. Here, we report current efficacy rates of Cemi in combination with paclitaxel followed by AC.

Methods: Women with tumors ≥ 2.5cm were eligible for screening. Only HER2 negative (HER2-) patients were eligible for this treatment; HR positive (HR+) patients had to be MP high risk. Treatment included paclitaxel 80 mg/m2 IV weekly x 12 and Cemi 350 mg IV given q3weeks x 4, followed by doxorubicin/cyclophosphamide (AC) every 2 weeks x 4. The control arm was weekly paclitaxel x 12 followed by AC every 2-3 weeks x 4. All patients undergo serial MRI imaging; and imaging response (at 3 weeks, 12 weeks and prior to surgery) were used along with accumulating pCR data to continuously update and estimate pCR rates for trial arms. Analysis was modified intent to treat. Patients who switched to non-protocol therapy count as non-pCR. The goal is to identify (graduate) regimens with ≥85% Bayesian predictive probability of success (i.e. demonstrating superiority to control) in a future 300-patient phase 3 neoadjuvant trial with a pCR endpoint within responsive signatures. Cemi was eligible to graduate in 3 pre-defined signatures: HER2-, HR-HER2-, and HR+HER2-. To adapt to changing standard of care, we constructed “dynamic controls” comprising ‘best’ alternative therapies using I-SPY 2 and external data and estimated the probability of Cemi being superior to the dynamic control.

Results: 60 HER2- patients (28 HR+ and 32 HR-) received Cemi arm treatment. The control group included 357 patients with HER2- tumors (201 HR+ and 156 HR-) enrolled since March 2010. Cemi graduated in HR-/HER2- signature. Estimated pCR rates (as of June 2022) are summarized in the table.

Immune-related endocrine disorders include: hypothyroid (14.5%), adrenal insufficiency (10%), hyperthyroid (4.8%),) and thyroiditis (3.2%). Only one grade 3 adrenal insufficiency was observed. All immune related AE’s were manageable. Additional biomarker analyses are ongoing and will be presented at the meeting. Response predictive subtypes (Immune+ vs Immune-) and additional predictive biomarkers were assessed. Associations with pCR will be presented at SABCS.

Conclusion: The I-SPY 2 study aims to assess the probability that investigational regimens will be successful in a phase 3 neoadjuvant trial. Anti-PD-1 therapy with Cemi resulted in a higher predicted pCR rate in HR-/HER2- 55 rate% disease compared to control at 29%. Immune-mediated AE’s were observed. This data is consistent with previously published data using check point inhibitors in early-stage HR-/HER2- breast cancer.

Estimated pCR rates

Citation Format: Erica Stringer-Reasor, Rebecca A. Shatsky, Jo Chien, Anne Wallace, Judy C. Boughey, Kathy S. Albain, Hyo S. Han, Rita Nanda, Claudine Isaacs, Kevin Kalinsky, Zahi Mitri, Amy S. Clark, Christos Vaklavas, Alexandra Thomas, Meghna S. Trivedi, Janice Lu, Smita Asare, Ruixiao Lu, Maria Pitsouni, Amy Wilson, Jane Perlmutter, Hope Rugo, Richard Schwab, W. Fraser Symmans, Nola M. Hylton, Laura Van ’t Veer, Douglas Yee, Angela DeMichele, Donald Berry, Laura J. Esserman, I-SPY Investigators. PD11-01 Evaluation of the PD-1 Inhibitor Cemiplimab in early-stage, high-risk HER2-negative breast cancer: Results from the neoadjuvant I-SPY 2 TRIAL [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 PD11-01.

Abstract P6-01-20: Luminal androgen receptor subtype and M2 macrophage signatures strongly associate with low pathological complete response rates and poor outcomes in patients with triple negative breast cancer receiving neoadjuvant chemotherapy

Background: Triple negative breast cancers (TNBC) are a heterogeneous group of cancers and it is difficult to predict which patients will respond to neoadjuvant chemotherapies (NACT). Achieving pathologic complete response (pCR) to NACT is prognostically favorable, whereas lack of pCR is associated with high rates of recurrence and death from TNBC. Currently, there is no universally accepted biomarker to predict TNBC response to NACT. Methods: We analyzed 25 in-house TNBC biopsies that were treated with neoadjuvant adriamycin (A), cyclophosphamide (C) and paclitaxel (T) and 31 residual TNBC after NACT-ACT using RNA-seq data from macro-dissected tumor tissues from formalin fixed paraffin embedded (FFPE) blocks. Raw reads were mapped to the Human reference genome GRCH38 using the kallisto aligner v0.46.1. Immune infiltrate fractions were estimated using the Cibersort algorithm derived from the LM22 gene-signature matrix of 22 hematopoietic cell types. TNBCtype-4 classification of samples was determined calculating the enrichment of gene-sets for: Luminal Androgen Receptor (LAR), Basal-like 1 and 2 (BL1, BL2), Mesenchymal(M). Overall immune-infiltrate analysis and cancer-intrinsic subtyping were conducted independently on each transcriptional profile. Results were validated by running our novel analyzing protocol in independent cohorts including 182 TNBC cases treated with NACT-ACT from a published Vanderbilt cohort and 179 TNBC cases from the TCGA database. Results: Twenty one (68%) of the 31 residual TNBC after neoadjuvant ACT were luminal androgen receptor (LAR) subtype and significantly enriched in M2 macrophage signature. The LAR subtype and monocyte or M2 macrophage signaturesstrongly associated with lack of pCR in the 25 TNBC biopsy cases and 182 Vanderbilt TNBC cases treated with NACT-ACT. Survival analysis of 179 TNBC cases from the TCGA database showed a significant association of LAR subtype and M2 macrophage signature with worse survival. Conclusions: We developed a novel RNA-seq analyzing protocol that combines tumor subtype and immune profile. The LAR subtype and M2 macrophage signatures strongly associated with lack of pCR and worse survival in TNBC patients when treated with NACT-ACT. Both tumor subtype and immune profile should be considered in biomarker development and further studied in specimens from patients treated with modern chemoimmunotherapy regimens.

Citation Format: Jane Meisel, Eugene Douglass, Kevin Kalinsky, Lyra M. Griffiths, Zaibo Li, Xiaoxian Li. Luminal androgen receptor subtype and M2 macrophage signatures strongly associate with low pathological complete response rates and poor outcomes in patients with triple negative breast cancer receiving neoadjuvant chemotherapy [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 P6-01-20.

Abstract P4-01-42: Pooled analysis of post-progression treatments after first-line ribociclib + endocrine therapy in patients with HR+/HER2− advanced breast cancer in the MONALEESA-2, -3, and -7 studies

Background: The MONALEESA (ML) studies showed significant PFS & OS benefits for 1L ribociclib (RIB) + endocrine therapy (ET) in patients (pts) with pre/peri & postmenopausal advanced breast cancer. The benefit of RIB beyond study treatment (tx) was also observed, with improvements in PFS2 & delays in time to 1st subsequent chemotherapy (CT). While there is currently no preferred tx for the next line post-progression on a CDK4/6 inhibitor (CDK4/6i), except alpelisib in pts with a PIK3CA mutation, guidelines encourage multiple lines of ET or ET-based therapies before switching to CT (except for visceral crisis). This pooled exploratory analysis of the ML studies examined outcomes of various tx strategies post progression on RIB + ET.

Methods: Data from pts receiving 1L therapy in ML-2, -3, & -7 (NSAI cohort only & excluding pts with early relapse [≤ 12 mo after end of (neo)adjuvant ET] whose prognosis is closer to that of 2L pts) were pooled & pts receiving 1st subsequent therapies after progression were analyzed. Three groups of subsequent therapies were assessed: ET only, CT, & targeted therapy. Subsequent CT comprises CT +/- any other therapy; targeted therapy includes CDK4/6i, mTORi, PI3Ki, AKTi, etc, +/- ET. Subsequent CT & targeted therapy groups are mutually exclusive. Median duration of study tx, 1st subsequent therapy, & OS (from randomization to death) were analyzed by KM methods. Weighted Cox regressions were performed using inversed propensity scoring matching method (inverse probability tx weighting [IPTW]) to ensure compatible pt characteristics between tx arms. These are not randomized comparisons; only baseline characteristics were used for the estimation of propensity scores in the IPTW, imbalance of prognostic factors at progression may exist.

Results: Median follow-up time was 74 mo. 461 pts treated with RIB (81%) & 440 (86%) with PBO discontinued study tx & received a subsequent therapy. In the RIB arms, the most common 1st subsequent therapies were ET only (40%), CT (29%), combination with targeted therapy (28%), & other (4%); for the PBO arms, 34% received CT as a 1st subsequent therapy & 31% each received ET only or combination with targeted therapy (5% received other). In 14% & 20% of pts in the RIB & PBO arms, the 1st subsequent therapy was a CDK4/6i, of these 31% & 12% were RIB. In general, regardless of type of 1st subsequent therapy, the duration of both the study tx & the 1st subsequent therapy was longer for pts treated with RIB vs PBO (Table). In both RIB & PBO arms, pts who received subsequent CT had the shortest duration on study tx, whereas those who received subsequent targeted therapy combination had the longest. Among pts on 1L RIB + ET, after matching pre-randomization baseline characteristics, subsequent CDK4/6i use was associated with the longest mOS (84 [84-NE] mo), followed by ET only (60 [51-68] mo), then a non-CDK4/6i targeted therapy (52 [43-72] mo); post-progression CT was associated with the shortest mOS (37 [32-48] mo).

Conclusions: This large, pooled analysis of the ML studies shows that, in general, duration of any subsequent therapy was numerically longer post-1L RIB + ET vs PBO + ET, & subsequent CT was used less frequently for pts on RIB vs PBO. Both findings confirm that upfront tx with RIB does not worsen pt outcomes. This trend in enhancement of outcomes of subsequent therapies seen with 1L RIB suggests a post-tx effect that merits further exploration.

Abstract P3-07-22: Presurgical Trial of Metformin plus Atorvastatin in Women with Operable Breast Cancer

Introduction:

Metformin is an oral anti-diabetic agent that exhibits direct anti-proliferative effects on pre-clinical models through activation of the AMPK pathway. However, pre-surgical studies of metformin alone among women with operable breast cancer have not consistently shown reductions in tumor proliferation, and adjuvant metformin in women with high-risk operable breast cancer did not improve invasive disease-free survival compared with placebo. Dysregulation of the mevalonate pathway of cholesterol synthesis can also lead to cell proliferation, and inhibition of HMG-CoA reductase by statins can decrease tumor proliferation. There is close interaction between the AMPK and mevalonate pathways, and dual therapy with a statin and metformin might be synergistic to decrease cell proliferation. We evaluated the effect of combination therapy with metformin plus atorvastatin on markers of proliferation (i.e. Ki67 proliferation index) in women with operable breast cancer.

Methods:

We conducted an open-label, single-arm presurgical “window of opportunity” study of metformin plus atorvastatin in non-diabetic women age 21+ years with newly-diagnosed stage 0-III operable breast cancer at Columbia University Irving Medical Center (CUIMC). Enrolled patients received metformin 1500mg oral [p.o.] daily (500mg in the morning/1000mg in the afternoon) and atorvastatin 80mg p.o. nightly for up to 4 weeks before breast surgery. The primary endpoint was change in Ki67 proliferation index from baseline (diagnostic biopsy) to post-treatment (surgical specimen). Secondary endpoints included change in body mass index (BMI), waist and hip circumferences, tumor assessment of AMPK/mTOR signaling and apoptosis, and reduction of fasting markers of the insulin growth factor pathway. Paired t-tests were conducted to assess difference in ln(Ki67) pre- and post-therapy, as well as differences in absolute Ki67, BMI, and waist/hip circumferences pre- and post-therapy, at a level of significance of 0.05.

Results:

Between Nov. 2013 and Jan. 2018, 22 women were enrolled, and two withdrew consent prior to study treatment. Among evaluable participants (n=20), 45% were Hispanic with median age 56 years (range, 33-73) and median baseline BMI 28.4 kg/m2 (range, 22.5-45.8). All had hormone receptor-positive (HR+), HER2-negative breast cancer, and 16 (80%) had invasive cancer. Median time on study treatment was 11 days (range, 5-29). Changes in Ki67 and anthropomorphic measures are shown in Table 1. There was no significant change in BMI, waist or hip circumference with study treatment. Among women with available Ki67 measurements (n=11), there was no significant difference in pre- and post-treatment ln(Ki67) (p=0.25). There was a numeric decrease in absolute Ki67, though statistical significance was not reached (p=0.09).

Discussion:

There was a numeric reduction in absolute Ki-67 with presurgical metformin plus atorvastatin in patients with newly diagnosed HR+/HER2- breast cancer, although our analysis was limited by small sample size and statistical significance was not achieved. There was no difference in ln(Ki67) or anthropometric measurements. Analyses of additional tissue and serum biomarkers, including markers of insulin resistance, are ongoing to identify associations with absolute Ki67

Table 1

Citation Format: Julia E. McGuinness, Katherine D. Crew, Meghna S. Trivedi, Melissa K. Accordino, Shing M. Lee, Hua Guo, Hanina Hibshoosh, Dawn Hershman, Kevin Kalinsky. Presurgical Trial of Metformin plus Atorvastatin in Women with Operable 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 P3-07-22.

Abstract GS1-04: Patient-reported cognitive impairment in women participating in the RxPONDER trial (SWOG S1007) by menopausal status

Introduction: Breast cancer treatment is associated with cancer-related cognitive impairment (CRCI). However, the differential effect of endocrine therapy (ET) vs chemotherapy followed by endocrine therapy (CET), including the impact of menopausal status, on CRCI is not well understood.

Methods: Participants (pts) with hormone receptor positive, HER2 negative breast cancer with 1-3 positive lymph nodes and an Oncotype DX recurrence score of 0-25 enrolled in the RxPONDER trial were randomly assigned to ET alone versus CET. Until the health-related quality of life (HRQoL) accrual goal was reached, English speaking pts in the US were invited to complete HRQoL questionnaires including the 8-item PROMIS Perceived Cognitive Function Concerns (PCF) Short Form questionnaire shortly after randomization (baseline), as well as 6, 12, and 36 months after baseline. Analysis of measures of anxiety and fatigue is presented separately. Standardized T scores (mean 50; SD 10) for PCF were computed with higher scores indicating less cognitive impairment. The primary endpoint of this exploratory analysis was to compare mean PCF T scores by treatment arm and menopausal status. Separately by menopausal status, a generalized estimating equations (GEE) model was fit to the three timepoints adjusting for baseline to estimate the difference between treatment arms and whether there was a time trend over the three follow-up measures.

Results: The HRQoL accrual exceeded the goal of 500 patients, with 74% of pts participating voluntarily until the QOL invitation was removed from the protocol (Dec 1, 2012). A total of 139 pre and 429 postmenopausal pts completed the questionnaires at baseline. T scores were similar between ET and CET arms at baseline [Table 1]. In the ET arm, T scores decreased from baseline to 6 and 12 months but recovered to baseline at 36 months. In the CET arm, T scores decreased from baseline to 6 months and 12 months but did not return to baseline at 36 months. The mean score difference between CET and ET over time was -3.02 (p=0.01) and -2.36 (p=0.003) for pre and postmenopausal pts, respectively. Adjusting for baseline, there was no significant time trend over the three follow-up periods for either premenopausal (p=0.12) or postmenopausal (p=0.49) pts. Dropoff occurred over time with 79%, 76%, 60% of pts at baseline participating at 6, 12, and 36 months. Complete endocrine treatment adherence data are not yet available at each timepoint.

Conclusion: Chemoendocrine therapy has a greater negative effect on patient-reported CRCI compared to ET alone in both pre- and post-menopausal pts and it is sustained over 36 months. Interventions to prevent or treat CRCI are needed to improve the long-term quality of life of patients treated with CET.

Table 1. Comparisons of mean Cognitive Function score by treatment arm and menopausal status.

Citation Format: Irene Kang, Jamie K. Forschmiedt, Michelle M. Loch, William E. Barlow, Danika L. Lew, Julie R. Gralow, Funda Meric-Bernstam, Kathy S. Albain, Daniel F. Hayes, Nancy U. Lin, Edith A. Perez, Lori J. Goldstein, Priya Rastogi, Anne F. Schott, Steven Shak, Priyanka Sharma, Jieling Miao, Debu Tripathy, Lajos Pusztai, Gabriel N. Hortobagyi, Kevin Kalinsky, N. Lynn Henry. Patient-reported cognitive impairment in women participating in the RxPONDER trial (SWOG S1007) by menopausal status [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 GS1-04.

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 P2-20-15: Proteolytic regulation of CD73 by TRIM2 orchestrates tumor immunogenicity

Proteolytic regulation of CD73 by TRIM2 orchestrates tumor immunogenicity Ziyi Fu1,2, Siqi Chen3, Yueming Zhu4, Donghong Zhang4, Ping Xie3, Qiao Jiao4, Shipeng Xu1, Yifan Xue6, Xinhua Lu6, Xinxin Song7, Massimo Cristofanilli8, William J Gradishar3, Kevin Kalinsky5, Yongmei Yin2, Bin Zhang3 and Yong Wan4,5* 1Department of Obstetrics and Gynecology, Department of Pharmacology, Robert H. Lurie Comprehensive Cancer Center, Northwestern University Feinberg School of Medicine, USA. 2Department of Oncology, The First Affiliated Hospital of Nanjing Medical University, China 3Department of Medicine, Robert H. Lurie Comprehensive Cancer Center, Northwestern University Feinberg School of Medicine, USA. 4Department of Pharmacology and Chemical Biology, Winship Cancer Institute, Emory University School of Medicine, USA. 5Department of Hematology and Medical Oncology, Winship Cancer Institute, Emory University School of Medicine, USA. 6Department of Biomedical Informatics, University of Pittsburgh School of Medicine, USA. 7Department of Surgery, UT Southwestern Medical Center, Dallas, TX, USA. 8Department of Medicine, Weill Cornell Medicine, USA. ABSTRACT Despite the rapid utilization of immunotherapy, emerging challenges to the current immune checkpoint blockade need to be resolved. Here, we report that uncontrolled elevation of CD73 levels due to its aberrant turnover is tightly correlated with poor prognosis in immune-cold triple negative breast cancers (TNBCs), which impedes the efficacy for chemotherapy and immunotherapy. We have identified TRIM21 as a E3 ligase that governs CD73 destruction. Disruption of TRIM21 stabilizes CD73 that in turn enhances CD73-catalyzed production of adenosine, resulting in the suppression of CD8+ T cell function. The immunostaining demonstrated the cytosolic colocalization between TRIM21 and CD73. Molecular mapping further identified the amino acid stretches from 340-476 on TRIM21 and residues from 176–224 on CD73 mediated the interaction between TRIM21 and CD73. Replacement of lysine 133, 208, 262 and 321 by arginine on CD73 attenuated CD73 ubiquitylation and degradation. Moreover, TRIM21 is upregulated but CD73 is downregulated in response to IFN- secreted from activated CD8+ T cells in a feedback manner. Importantly, in preclinical animal models, diminishing of CD73 ubiquitylation remarkably promotes tumor growth and impedes antitumor immunity. In addition, a TRIM2hight/CD73low signature in a subgroup of human breast malignancies was associated with a favorable immune profile. Collectively, our findings uncover a novel mechanism that governs CD73 proteolysis and point to a new therapeutic strategy by modulating CD73 ubiquitylation.

Citation Format: Ziyi Fu, Yueming Zhu, Kevin Kalinsky, Yong Wan. Proteolytic regulation of CD73 by TRIM2 orchestrates tumor immunogenicity [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 P2-20-15.

Abstract P6-01-23: Role of tumor infiltrating lymphocytes and PD-L1 expression in the response to eribulin and pembrolizumab in metastatic triple negative breast cancer (mTNBC) on the ENHANCE1 trial

Background Treatment with combination chemo-immunotherapy has become the front-line standard for eligible patients with PD-L1 positive mTNBC. PD-L1 is the only approved biomarker for pembrolizumab in metastatic breast cancer for response to combination chemo-immunotherapy, however given that it is not predictive of response in all cases additional biomarkers are needed. Tumor infiltrating lymphocytes (TILs) have been shown to be both predictive and prognostic in operable TNBC, but there are fewer data regarding the role of TILs in mTNBC. In this study we report the associations between TILs and outcomes in patients treated prospectively on the ENHANCE-1 study with eribulin and pembrolizumab. Methods ENHANCE-1 was a single arm phase Ib/II trial which evaluated the efficacy and safety of eribulin and pembrolizumab in 167 patients (pts) with mTNBC who had received 0-2 prior lines of therapy (66 pts in the first line setting [stratum 1] and 101 pts with 1-2 prior lines of therapy [stratum 2]). Objective response rate (ORR) was defined as percentage of pts with either complete response (CR) or partial response (PR) by RECIST 1.1. The ORR was 25.8% in stratum 1 and 21.8% in stratum 2. Stromal TILs (sTIL) and intratumoral TILs were evaluated on whole slide H&E sections from biopsy specimens used for enrollment on ENHANCE-1 by breast pathology according to the International TILs Working Group guidelines. PD-L1 positivity was determined via immunohistochemistry using the Agilent 22C3 antibody. We also assessed TIL density digitally using machine learning classifiers to identify tumor/stromal tissue areas and individual lymphocytes. Results We found that there was statistically significant increase in sTIL counts in responders compared to non-responders in stratum 1 (p=0.002) but not in stratum 2 (p=0.99). We did not find any associations between intratumoral TILs and response. Quantitative PD-L1 scoring via combined proportion score (CPS) was also positively associated with response in stratum 1 (p=0.01) but not in stratum 2 (p=0.34). We also find that sTIL counts are most correlated to CPS scores (continuous) for non-responders within stratum 1 (R2=+0.55, p&lt; 0.01). Conclusion In this population of patients with mTNBC treated prospectively with eribulin and pembrolizumab, sTILs and PDL1 CPS were each individually associated with a positive response in patients treated with front-line combination chemo-immunotherapy. Neither was predictive for patient response in stratum 2. One important caveat is the biopsies were not required immediately prior to enrollment, possibly confounding the tumor microenvironment (TME) at the time of analysis. Our data contribute to emerging data that sTILs can act as a biomarker for response to immune checkpoint inhibition when utilized in the front-line setting for mTNBC. Further characterization of the TME via quantitative immunofluorescence is ongoing. This study was funded by Eisai IIS-E7389

Citation Format: Mathew Kearney, Hua Guo, Rami Vanguri, Qi Wang, Michelle Garlin, Courtney Connelly, Kevin Kalinsky, Eileen P. Connolly. Role of tumor infiltrating lymphocytes and PD-L1 expression in the response to eribulin and pembrolizumab in metastatic triple negative breast cancer (mTNBC) on the ENHANCE1 trial [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 P6-01-23.

Abstract HER2-19: HER2-19 Impact of HER2 low status on clinical outcomes in participants with 1-3 positive lymph nodes, HR+/HER2- breast cancer with recurrence score &lt;/25 randomized to endocrine therapy +/- chemotherapy: results from SWOG S1007 (RxPONDER)

Background: HER2 low breast cancer, defined as tumors with HER2 IHC expression 1+ or 2+ without HER2 gene amplification, represents a potential new therapeutic subgroup of metastatic breast cancer (BC). However, the clinical significance of HER2 low status in early BC remains unclear. Previously, the RxPONDER trial (NCT01272037), a prospective, randomized trial of endocrine therapy (ET) vs. chemoendocrine therapy (CET) in women with lymph node positive (LN+) BC, demonstrated invasive disease-free survival (IDFS) with ET vs CET varies by menopausal status. We evaluated the impact of HER2 low vs zero status in the RxPONDER trial (SWOG S1007), stratified by menopausal status and treatment groups.

Methods: Eligibility criteria included women &gt;/18 years of age with hormone receptor-positive (HR+), HER2-negative (HER2-) BC, Recurrence Score (RS) &lt;/25, 1-3+ LN and no contraindications to taxane and/or anthracycline based CT. The impact of HER2 low status and other baseline clinicopathological features on clinical outcomes were evaluated using covariates in Cox regression analysis. HER2 IHC status was per local testing. HER2 low was defined as IHC 1+ or IHC 2+ without HER2 gene amplification, and HER2 zero was defined as IHC 0. The primary endpoint was IDFS, defined as the time from the date of randomization to the date of a first invasive recurrence (local, regional, or distant), a new invasive primary cancer (breast cancer or another type of cancer), or death from any cause. Secondary objectives included distant-relapse free survival (DRFS).

Results: Among the 4,983 eligible participants, 4,588 had IHC HER2 status available. 52% of 2,052 pre-menopausal women had HER2 low BC and 57% of 3,042 post-menopausal women had HER2 low BC. There was a small, but statistically significant (p=0.03) difference, in RS between HER2 low (mean 14.5) and HER2 zero (mean 14.1) status. The proportion of participants with HER2 low and zero were balanced between treatment group assignment (CET vs ET). Among pre-menopausal women adjusting for RS, CET led to an observed improvement in IDFS among both HER2 low (HR=0.67; 95% CI 0.43-1.04) and HER2 zero subgroups (HR=0.57; 95% CI 0.36-0.89) (interaction p=0.55). Similarly, among post-menopausal women, there was no difference in IDFS between CET vs ET among both HER2 low (HR=0.98; 95% CI 0.75-1.29) and HER2 zero (HR=1.12; 95% CI 0.80-1.56) subgroups (interaction p=0.57). In multivariable analysis, adjusting for treatment arm, RS, and menopausal status, HER2 low status was not associated with worse IDFS compared to HER2 zero status (HR=0.93; 95% CI 0.78-1.11). Additionally, no differences were noted in DRFS.

Conclusion: HER2 low or zero status had no impact on clinical outcomes with CET vs ET among pre-menopausal or post-menopausal women with HR+/HER- BC with 1-3+ LNs and RS &lt;/25. HER2 low evaluation should not be currently used for CET vs ET clinical decision making among patients with HR+/HER2- breast cancer with 1-3+ LN and RS &lt;/25. Further research on the role of HER2 low status in other settings may be warranted.

Citation Format: Laura M. Spring, William E. Barlow, Aditya Bardia, Priyanka Sharma, Lajos Pusztai, Gabriel N. Hortobagyi, Kevin Kalinsky. HER2-19 Impact of HER2 low status on clinical outcomes in participants with 1-3 positive lymph nodes, HR+/HER2- breast cancer with recurrence score &lt;/25 randomized to endocrine therapy +/- chemotherapy: results from SWOG S1007 (RxPONDER) [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 HER2-19.

Abstract OT2-10-03: HCRN BRE 19-433: A Multi-institutional Phase II Study to Evaluate Efficacy and Safety of TAlazoparib, Radiotherapy and Atezolizumab in gBRCA 1/2 negative Patients with PD-L1+ Metastatic Triple Negative Breast Cancer (TARA)

Background Although immunotherapy (IO) in combination with chemotherapy has improved progression free and overall survival in patients with PD-L1+ metastatic triple negative breast cancer (mTNBC), prognosis remains poor. A potential therapeutic strategy to restore sensitivity to IO in patients with progressive disease is to introduce agents that re-sensitize the immune system to IO leading to a more tumor-specific and less toxic treatment in the second-line setting or beyond. Both talazoparib, a PARP inhibitor, and radiation (XRT) independently increase PD-L1 expression on the tumor cell surface resulting in heightened sensitivity to IO agents like atezolizumab, a PD-L1 inhibitor. Although a local treatment, XRT has the ability to produce an abscopal effect resulting in systemic shrinkage of non-irradiated tumors outside/distant to the XRT field, a phenomenon observed in patients receiving concurrent IO. While talazoparib is standard treatment in patients with gBRCA1 and 2 mutations, it is also a potent radiosensitizing agent that suppresses homologous recombination and PARP-1-dependent nonhomologous end joining (NHEJ) repair while promoting error-prone alt-NHEJ. When combined with IO, talazoparib can amplify immune responses by generating immunogenic neo-antigens independent of gBRCA1/2 status. We, therefore, hypothesize that the combination of talazoparib, XRT, and atezolizumab will re-sensitize mTNBC tumors to IO and promote a durable tumor-specific response that spares patients from toxicities associated with traditional chemotherapy regimens. Methods This is a Phase II multi-institutional study designed to assess efficacy and safety of talazoparib, high dose XRT, and atezolizumab given in the second-, third-, or fourth-line settings to patients with mTNBC that is PD-L1 positive. A total of 23 patients with mTNBC who do not carry gBRCA pathogenic variants will be enrolled. All patients will be treated with induction talazoparib of 1mg PO daily starting Day 1 of a 28-day cycle. Patients will then receive 8 Gy x 3 fractions to 1-4 metastatic lesions QOD beginning Day 12, 13, or 14. Atezolizumab will be given intravenously (840 mg)) on Day 15 of the 1st cycle and then on Day 1 and Day 15 of the subsequent cycles. Talazoparib and atezolizumab treatment will continue until progression or severe toxicity. The primary endpoint is objective response rate (ORR) in non-irradiated lesions 8 weeks after the first dose of atezolizumab. Key inclusion criteria include biopsy proven mTNBC (ER&lt; 10%, PR&lt; 10%, Her2-) with at least 2 extracranial metastatic lesions. Patients must have at least 1 extracranial metastatic lesion amenable to high dose radiotherapy and at least one additional extracranial lesion of measurable disease by Response Evaluation Criteria in Solid Tumors (RECIST v1.1) that will not receive radiotherapy. Tumors must be PD-L1 positive as defined as &gt;1% on IHC using the SP142 Ventana Assay. Key exclusion criteria include patients with germline BRCA pathogenic variants, more than three previous lines of chemotherapy treatment in the advanced setting with or without IO, and breast cancer progression within the first 3 months of previous IO treatment for non-metastatic or metastatic breast cancer. Sample size was determined using Simon’s 2-stage Minimax design to detect a 20% increase in ORR. The null hypothesis that the true response rate among gBRCA1/2 negative patients of 10% will be tested against a one-sided alternative. Inflammatory cytokines, circulating B cells, and ctDNA will be collected for correlative analysis. Enrollment began in April 2021. The study is managed by the Hoosier Cancer Research Network and is open to accrual at Emory University and University of Alabama at Birmingham. Clinical trial information: NCT04690855

Citation Format: Mylin A. Torres, Kevin Kalinsky, Erica Stringer-Reasor, Ahmed Elkhanany, Jolinta Lin, David M. Schuster, Sarah Friend, Jeffrey Switchenko, Manali Bhave. HCRN BRE 19-433: A Multi-institutional Phase II Study to Evaluate Efficacy and Safety of TAlazoparib, Radiotherapy and Atezolizumab in gBRCA 1/2 negative Patients with PD-L1+ Metastatic Triple Negative Breast Cancer (TARA) [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 OT2-10-03.

Abstract P3-09-01: Characterization of residual disease after neoadjuvant selective estrogen receptor degrader (SERD) therapy using tumor organoids in the I-SPY Endocrine Optimization Protocol (EOP)

Background: Treatment of estrogen receptor (ER)-positive breast cancer with selective estrogen receptor degraders (SERDs) frequently results in the loss or reduction of ER expression. Whether these changes are due to on-target effects of SERDs degrading ER or arise as a mechanism of tumor resistance with associated changes in cellular phenotypes remains unknown. It is critical to distinguish between these possibilities to accurately assess treatment response and determine the most appropriate subsequent therapy. To this end, we created and conducted molecular analyses on patient-derived organoid cultures from post-treatment tissue in patients receiving neoadjuvant SERD therapy for early-stage ER+ breast cancer in the I-SPY2 Endocrine Optimization Protocol (EOP). Methods: The I-SPY2 EOP study is a prospective, randomized substudy within the I-SPY TRIAL testing the oral SERD amcenestrant alone or in combination with letrozole or abemaciclib in stage 2/3 ER+ Her2-negative breast cancer. Enrollment is ongoing, with patients receiving amcenestrant neoadjuvantly for 6 months until the day before surgery. Tumor tissue is collected at baseline, 3 weeks, and at surgery. Organoids were generated from post-treatment surgical samples. Organoid cultures were optimized based on established methods (Dekkers et al., Nature Protocols, 2021) to assess ER levels and activity. Pre- and post-treatment tissue samples were also assessed for ER, PR, Ki67, and GATA3, a luminal marker and transcription factor that is functionally linked with ER, via immunohistochemistry. Results: In 7 patients with both pre- and post-treatment tissue samples including fresh surgical samples for organoid generation, the ER in baseline tumor tissue was &gt;=90% in all patients, PR ranged from 40-90%, and Ki67 ranged from 5-30%. In post-treatment surgical tissue from these cases, ER ranged from 0-30%, PR from 0-50%, Ki67 from &lt; 1%-10%, and GATA3 was positive in 5 of 5 cases tested to-date. The creation of organoids from residual disease at surgery was attempted for these 7 patients, with organoids successfully propagated in 5 cases thus far. 3 of 5 organoid cultures were ready for analysis and in all cases strong ER and PR expression in organoids was observed after culture for &gt; 1 month in the absence of amcenestrant. Detailed gene expression profiling (including Mammaprint/Blueprint) and gene set enrichment analyses (GSEA) to assess for intrinsic breast cancer subtype and ER activity in each sample and corresponding organoid culture are in progress and will be reported with the full dataset. Conclusion: Patient-derived organoid culturing of residual disease after neoadjuvant endocrine therapy is feasible. Neoadjuvant treatment with a SERD can render ER and PR low or absent at the time of surgical resection, which does not necessarily imply the presence of endocrine therapy resistant disease. The use of organoids and additional IHC markers (GATA3) demonstrate that receptor negativity may be an indicator of the drug hitting its target, suggesting ER signaling is still intact. In general, patient-derived tumor organoid cultures modeling residual disease states can be a useful adjunct to existing methods used to monitor the effects of neoadjuvant endocrine therapy and is being explored in the I-SPY EOP trial.

Citation Format: Jennifer Rosenbluth, Christopher J. Schwartz, Tam Binh Bui, Shruti Warhadpande, Pravin Phadatare, Sigal Eini, Michael Bruck, Julissa Molina-Vega, Kami Pullakhandam, Nicole Schindler, Lamorna A. Brown Swigart, Christina Yau, Gillian Hirst, Rita Mukhtar, Karthik V. Giridhar, Olufunmilayo I. Olopade, Kevin Kalinsky, Cheryl A. Ewing, Jasmine M. Wong, Michael D. Alvarado, Laura Van’t Veer, Laura J. Esserman, Jo Chien. Characterization of residual disease after neoadjuvant selective estrogen receptor degrader (SERD) therapy using tumor organoids in the I-SPY Endocrine Optimization Protocol (EOP) [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 P3-09-01.

Abstract PD9-09: Molecular differences between younger versus older estrogen receptor positive/human epidermal growth factor receptor-2 negative breast cancers

Background: The RxPONDER and TAILORx trials demonstrated benefit from adjuvant chemotherapy in patients &lt; 50 years with node-positive breast cancer and Recurrence Score (RS) 0-25, and with node-negative disease and RS 16-25, respectively. Neither trial showed benefit in older women with RS &lt; 26. It is unclear what explains the interaction between age and adjuvant chemotherapy benefit. Methods: We analyzed transcriptomic and genomic data from n=4,507 ER+/HER2- breast cancers to compare differences in estrogen receptor (ER), proliferation, and immune-related gene expressions, and somatic mutation patterns and mutation burden between younger (&lt; 50 years of age) and older (&gt;55 years) patients. We restricted our analysis to patients in the lower 80% range of in silico RS distribution to mimic the RxPONDER and TAILORx populations. Results: Five data sets were analyzed independently to assess consistency of results (TCGA n=530; microarray cohort A n=865; Cohort B n=609, METABRIC n=867, SCAN-B n=1636). Older patients had significantly higher somatic mutation burden and more frequent copy number gain in ESR1, LATS1, ARID1B, SGK1, and MYB genes (odds ratio [OR] &gt; 8.5, FDR&lt; 0.05), but lower frequency of GATA3 mutations (12% versus 26%, P&lt; 0.0001). Younger patients had higher rate of ESR1 copy number loss (OR: 0.45, FDR: 0.03). There was no difference in proliferation-related gene expression. ESR1 mRNA expression was significantly lower in younger women in all cohorts (P &lt; 0.001). A regression model of ESR1 mRNA expression using age and ER IHC positivity indicated that lower ER expression in younger patients is primarily driven by lower ESR1 mRNA per cancer cell and not by fewer ER positive cells. We also assessed four gene signatures associated with endocrine therapy sensitivity including a 4-gene ERS, a 7-gene ERS-Lum, a 106-gene ERS-Pos signature, and a 59-gene ERS-Neg signature associated with endocrine resistance. In the TCGA and METABRIC cohorts, the ERS, ERS-Lum, and ERS-Pos signatures were all lower (FDR&lt; 0.03) while the ERS-Neg signature was higher (FDR&lt; 0.001) in younger patients. Similarly, in both microarray cohorts, and in the SCAN-B-cohort, the ERS-Pos signature was lower and the ERS-Neg signature was higher in younger patients (FDR&lt; 0.002). Next, we assessed 4 different immune cell signatures that have been associated with response to chemotherapy. In the TCGA, B-cell, T-cell, Mast-cell, and TIS signatures were significantly higher (FDR&lt;.05). In the microarray Cohort-A, B cells and mast cells were significantly higher, and the T cell and TIS signatures showed a trend for higher expression. In Cohort-B, T cells, B cells, TIS, and dendritic cells signatures were significantly higher in younger patients. Significantly higher expression of immune gene signatures in younger patients were also seen in the METABRIC and SCAN-B data sets. The ER-related and immune-related gene signatures showed negative correlation and joint analysis defined three subpopulations in younger women: (i) immune-high/ER-low, (ii) immune-intermediate/ER-intermediate and (iii) immune-low/ER-intermediate, whereas in older women the dominant pattern was immune-low/ER-high. Conclusion: ESR1 mRNA and ER-associated gene expression is lower in ER positive cancers of younger compared to older patients, while immune infiltration is higher. The cytotoxic and endocrine effects of adjuvant chemotherapy could both contribute to the survival benefit seen in younger patients, but the relative contributions of these effects may vary by ER and immune phenotype. We hypothesize that in immune-high/ER-low cancers, the cytotoxic effect of chemotherapy may drive the benefit, whereas in immune-low/ER-intermediate cancers chemotherapy induced ovarian suppression may play a more important role.

Citation Format: Tao Qing, Thomas Karn, Mariya Rozenblit, Julia Foldi, Michal Marczyk, Naing Lin Shan, Kim Blenman, uwe Holtrich, Kevin Kalinsky, Funda Meric-Bernstam, Lajos Pusztai. Molecular differences between younger versus older estrogen receptor positive/human epidermal growth factor receptor-2 negative breast cancers [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 PD9-09.

Abstract GS5-03: Evaluation of anti-PD-1 Cemiplimab plus anti-LAG-3 REGN3767 in early-stage, high-risk HER2-negative breast cancer: Results from the neoadjuvant I-SPY 2 TRIAL

Background: I-SPY2 is a multicenter, phase 2 trial using response-adaptive randomization within biomarker subtypes defined by hormone-receptor (HR), HER2, and MammaPrint (MP) status to evaluate novel agents as neoadjuvant therapy for high-risk breast cancer. The primary endpoint is pathologic complete response (pCR). Cemiplimab is an anti-PD-1 inhibitor approved for the treatment of NSCLC and cutaneous basal and squamous cell CA. Lymphocyte activation gene 3 (LAG-3) binds MHC class II leading to inhibition of T-cell proliferation and activation and is often co-expressed with PD-1. REGN3767 is a fully humanized mAb that binds to LAG-3 and blocks inhibitory T-cell signaling. Concurrent blockade of LAG-3 with an anti-PD-1 may enhance efficacy of an anti-PD-1.

Methods: Women with tumors ≥ 2.5cm were eligible for screening. Only HER2 negative (HER2-) patients were eligible for this treatment; HR positive (HR+) patients had to be MP high risk. Treatment included Paclitaxel 80 mg/m2 IV weekly x 12 and Cemiplimab 350 mg and REGN3767 1600 mg both given q3weeks x 4, followed by doxorubicin/cyclophosphamide (AC) every 2 weeks x 4. The control arm was weekly paclitaxel x 12 followed by AC every 2-3 weeks x 4. Cemiplimab/REGN3767 was eligible to graduate in 3 of 10 pre-defined signatures: HER2-, HR-HER2-, and HR+HER2-. The statistical methods for evaluating I-SPY 2 agents has been previously described. To adapt to changing standard of care, we constructed “dynamic controls” comprising ‘best’ alternative therapies using I-SPY 2 and external data and estimated the probability of Cemiplimab/REGN3767 being superior to the dynamic control. Response predictive subtypes (Immune+ vs Immune-) were assessed using pre-treatment gene expression data and the ImPrint signature.

Results: 73 HER2- patients (40 HR+ and 33 HR-) received Cemiplimab/REGN3767 treatment. The control group included [357 patients with HER2- tumors (201 HR+ and 156 HR-) enrolled since March 2010. Cemiplimab/REGN3767 graduated in both HR-/HER2- and HR+/HER2- groups; estimated pCR rates (as of June 2022) are summarized in the table. Safety events of note for Cemiplimab/REGN3767 include hypothyroidism 30.8%, adrenal insufficiency (AI) 19.2%, hyperthyroidism 14.1%, pneumonitis 1.3%, and hepatitis 3.8%. All were G1/2 except for 6 (7.7%) G3 AI and 3 (3.8%) G3 colitis. Rash occurred in 62.8%, 9% G3 and 2 pts (2.6%) had pulmonary embolism. X% of adrenal insufficiency cases required replacement therapy. 40 patients (11 HR+ and 29 HR-) in Cemiplimab/REGN3767 were predicted Immune+; 32 (29 HR+ and 3 HR-) were predicted Immune-. In the HR+ group pCR was achieved in 10/11 (91%) patients with Immune+ subtype compared with 8/29 (28%) with Immune- subtype. Additional biomarker analyses are ongoing and will be presented at the meeting.

Conclusion: The I-SPY 2 study aims to assess the probability that investigational regimens will be successful in a phase 3 neoadjuvant trial. Dual immune blockade with a LAG-3 inhibitor and anti-PD1 therapy resulted in a high predicted pCR rate both in HR-/HER2- (60%) and HR+/HER2- (37%) disease. The novel Imprint signature identified a group of HR+ patients most likely to benefit from this active regimen.

Table 1: Estimated pCR rates

Citation Format: Claudine Isaacs, Rita Nanda, Jo Chien, Meghna S. Trivedi, Erica Stringer-Reasor, Christos Vaklavas, Judy C. Boughey, Amy Sanford, Anne Wallace, Amy S. Clark, Alexandra Thomas, Kathy S. Albain, Laura C. Kennedy, Tara B. Sanft, Kevin Kalinsky, Hyo S. Han, Nicole Williams, Mili Arora, Anthony Elias, Carla Falkson, Smita Asare, Ruixiao Lu, Maria Pitsouni, Amy Wilson, Jane Perlmutter, Hope Rugo, Richard Schwab, W. Fraser Symmans, Nola M. Hylton, Laura Van’t Veer, Douglas Yee, Angela DeMichele, Donald Berry, Laura J. Esserman, I-SPY Investigators. Evaluation of anti-PD-1 Cemiplimab plus anti-LAG-3 REGN3767 in early-stage, high-risk HER2-negative breast cancer: Results from the neoadjuvant I-SPY 2 TRIAL [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 GS5-03.

Abstract OT1-03-04: Datopotamab deruxtecan (Dato-DXd), a TROP2 antibody-drug conjugate, vs investigators’ choice of chemotherapy in previously-treated, inoperable or metastatic HR+/HER2– breast cancer: TROPION-Breast01

Background: Chemotherapy is the main treatment in patients with pre-treated endocrine-resistant HR+/HER2– metastatic breast cancer, but has limited efficacy and substantial toxicities. The antibody-drug conjugate Dato-DXd consists of a humanized IgG1 mAb targeting TROP2 attached via a stable cleavable linker to a topoisomerase I (TopI) inhibitor payload. Heavily pre-treated patients with metastatic triple-negative breast cancer in the TROPION-PanTumor01 (NCT03401385) study of Dato-DXd showed a manageable safety profile and highly encouraging objective response rates (ORR by blinded independent central review [BICR]: 34% in all patients; 52% in patients treatment-naïve to TopI inhibitor-based therapies). The metastatic HR+/HER2– breast cancer cohort of TROPION-PanTumor01 has completed enrollment (n=41); data are currently maturing. Trial design: TROPION-Breast01 (NCT05104866) is an ongoing, global, phase 3, open-label, randomized trial evaluating efficacy and safety of Dato-DXd vs investigators’ choice of chemotherapy (ICC) in patients with inoperable or metastatic HR+/HER2– breast cancer. Patients (n≈700) are randomized 1:1 to Dato-DXd 6 mg/kg IV Q3W or ICC (eribulin, capecitabine, vinorelbine, or gemcitabine) until progression. Adults with an ECOG performance status of 0–1, who experienced progression on or are unsuitable for endocrine therapy, and received 1–2 prior lines of standard-of-care chemotherapy in the inoperable or metastatic setting are eligible. Monotherapy treatment with inhibitors of mTOR, PD-[L]1, CDK4/6 and PARP do not count as prior chemotherapy lines. Patients must have ≥1 measurable lesion per RECIST 1.1 and an archival or fresh formalin-fixed and paraffin-embedded tumor sample. Clinically inactive brain metastases are permitted. Dual primary endpoints are progression-free survival (PFS) by BICR, and overall survival. Secondary endpoints include PFS per investigator, ORR, disease control rate, patient-reported outcomes, and Dato-DXd pharmacokinetics and immunogenicity. Exploratory endpoints include TROP2 expression and exposure–efficacy relationship. Patients are stratified by number of prior chemotherapy lines, prior CDK4/6 inhibitor use, and region. At the time of writing 236 patients have been enrolled across 19 countries.

Citation Format: Aditya Bardia, Kevin Kalinsky, Junji Tsurutani, Erika Hamilton, Joo Hyuk Sohn, Kyong Hwa Park, Yeon Hee Park, Seock-Ah Im, Keun Seok Lee, Daisy Dastur, Vincent Haddad, Sabrina Khan, Binghe Xu, Barbara Pistilli, Hope Rugo. Datopotamab deruxtecan (Dato-DXd), a TROP2 antibody-drug conjugate, vs investigators’ choice of chemotherapy in previously-treated, inoperable or metastatic HR+/HER2– breast cancer: TROPION-Breast01 [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT1-03-04.

Abstract GS1-01: Race and clinical outcomes in the RxPONDER Trial (SWOG S1007)

Introduction: Racial disparities in breast cancer (BC) outcomes continues to be a major health care challenge. The 21-gene recurrence score (RS) is an important tool to guide treatment (tx) decisions among women with early-stage BC. We report an analysis of clinical characteristics, survival outcomes and race in association with RS in participants (pts) in the RxPONDER trial.

Methods: We analyzed clinical outcomes with respect to race and ethnicity. Unreported race excluded 18.7% of the pts, with most due to privacy rules. The primary outcome was invasive disease-free survival (IDFS). Distant relapse-free survival (DRFS) was also evaluated. Analyses adjusted for assigned tx arm, RS, and grade were performed. There were too few events to include Native American/Pacific Islander (NAPI) women in the survival analyses.

Results: A total of 4,048 trial women with Hormone Receptor positive, HER2 negative (HR+/HER2-) BC, 1-3 involved axillary lymph nodes (LNs), RS ≤ 25 and known race/ethnicity were included in this analysis including the following: 2,833 non-Hispanic (NH) White pts (70%), 248 NH Black pts (6.1%), 610 Hispanic pts (15.1%), 324 Asian pts (8.0%), and 33 NAPI pts (0.8%). Asian and Hispanic women were younger than NH Whites (by 7.1 and 2.4 years, respectively) but NH Blacks did not differ in age. RS distribution did not differ among all racial subgroups (p=0.49). There were also no significant differences in tumor size (p=0.10) or number of positive LNs (p=0.26) across all racial groups. However, tumor grade was found to be significantly different with grade 3 tumors higher for NH Blacks (18.0%), NH NAPI (21.1%), and Hispanics (14.5%) vs. NH Whites (10.4%) and Asians (6.5%) (p&lt; 0.001). Overall five-year IDFS was lower for NH Blacks (87.0%) compared to that for Asians (93.9%), NH Whites (91.5%), and Hispanics (91.4%) (Table 1). A multivariable Cox model adjusting for RS and tx arm showed worse IDFS for NH Blacks compared to NH Whites (HR=1.38; 95% CI 1.00-1.90; p=0.048), although Asian pts had better IDFS than NH Whites (HR=0.65; 95% CI 0.44-0.97; p=0.034). In a separate analysis by menopausal status the magnitude of the IDFS hazard ratios (HRs) for NH Blacks was similar, although no longer statistically significant (premenopausal HR=1.37; 95% CI 0.69-2.72; postmenopausal HR=1.38; 95% CI 0.96-1.98). While there was no statistically significant interaction between NH Blacks vs. NH Whites and tx arm for either premenopausal (p=0.99) or postmenopausal women (p=0.44), adjusting for RS, the small number of events in the NH Black cohort, particularly in premenopausal women (n = 9 IDFS events), limit power and inference about differences in chemotherapy benefit. Among postmenopausal women, NH Blacks had worse DRFS compared to NH Whites (HR=1.69; 95% CI 1.12-2.53; p=0.01), adjusting for tx and RS. A similar trend was seen among premenopausal women (HR=1.74; 95% CI 0.79-3.82; p=0.17), although not statistically significant. Data on tx adherence over 5 years was not mature, although NH Blacks were more likely to accept tx assignment compared to NH Whites at randomization (93% vs. 86%, p=0.004).

Conclusion: Black women with HR+/HER2- BC, 1-3 involved LNs and RS ≤ 25 have worse outcomes compared to White women despite similar RS results. There was no significant interaction between NH Blacks vs. NH Whites and tx arm, although this analysis was limited due to sample size. There remains an important need for novel approaches to improve clinical outcomes particularly for NH Black Women.

Table 1. IDFS by Race and Ethnicity.

Citation Format: Yara Abdou, William E. Barlow, Julie R. Gralow, Funda Meric-Bernstam, Kathy S. Albain, Daniel F. Hayes, Nancy U. Lin, Edith A. Perez, Lori J. Goldstein, Stephen K. Chia, Sukhbinder Dhesy-Thind, Priya Rastogi, Emilio Alba, Suzette Delaloge, Anne F. Schott, Steven Shak, Priyanka Sharma, Danika L. Lew, Jieling Miao, Joseph M. Unger, Debu Tripathy, Lajos Pusztai, Gabriel N. Hortobagyi, Kevin Kalinsky. Race and clinical outcomes in the RxPONDER Trial (SWOG S1007) [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 GS1-01.

Abstract PD13-09: PD13-09 Clinical outcomes of patients with HR+ HER2- advanced breast cancer with early progression on CDK4/6 inhibitors

Background: CDK4/6 inhibitors (CDK4/6i) paired with endocrine therapy (ET) are considered first-line (1L) therapy for patients (pts) with HR+ HER2- advanced breast cancer (aBC). A minority of pts will demonstrate primary resistance to CDK4/6i, as characterized by early progression. Thymidine kinase 1 (TK1) is a cell-cycle regulated enzyme downstream of CDK4/6 and involved in nucleotide metabolism during DNA synthesis. Prior studies have shown TK1 may serve as a biomarker of response to CDK4/6i, with early TK1 activity (TK1a) suppression after initiation of CDK 4/6i therapy associated with improved PFS. Lack of TK1a suppression may be associated with primary resistance to CDK4/6i. In this study, we aim to analyze response to subsequent lines of therapy and overall survival (OS) of pts with early progression on 1L CDK4/6i. Methods: Pts with HR+ HER2- aBC from a phase II trial of an alternative schedule of palbociclib (palbo alt dosing trial NCT 3007979) and from a retrospective palbociclib study were included in this analysis. Pts in the palbo alt dosing trial underwent baseline and C1D15 TK1a analysis after initiation on CDK4/6i. C1D15 TK1a suppression was defined at TK1a &lt; 30 Du/L. Pts in the retrospective palbociclib study included pts receiving palbo as part of their standard of care 1L therapy for HR+ HER2- aBC at Washington University in Saint Louis from 2016 to 2021. Clinical information, including treatment start and stop dates on each of the next-line therapies, were collected from the electronic medical record. PFS was estimated by the treatment duration on a specified treatment regimen. Early progression on CDK4/6i was defined as PFS &lt; 6 mo. Best response was defined as next line of therapy with the numerically longest PFS. OS was defined as time to death from the initiation of CDK4/6i. Results: Of the 54 pts enrolled on the palbo alt dosing trial, 51 pts were evaluable for clinical benefit and 46 pts were evaluable for TK1a suppression rate at C1D15. 7 pts (15.2%) were found without TK1a suppression at C1D15. This lack of TK1a suppression on palbo was associated with a significantly shorter PFS (median PFS=3.1 mo) compared to not reached in pts with TK1a suppression at C1D15. We conducted clinical analysis on N=26 pts who exhibited early progression on CDK4/6i which included 10 pts from the palbo alt dosing trial and 16 from the retrospective study. The average subsequent line of therapies in this cohort was 3, with the most common second line (2L) therapy being chemotherapy (N=17, 65.4%) and ET (N=8, 30.8%). The median PFS for pts receiving 2L chemotherapy and ET was 4.09 mo and 3.64 mo, respectively. 10 pts received both chemotherapy and ET with 7 (70.0%) achieving best response with chemotherapy compared to 3 pts (30.0%) who achieved best response with ET. The median OS for the cohort was 14.6 mo. Conclusions: Early progression on CDK4/6i is associated with a particularly poor prognosis. In our cohort, the median OS was far below the expected median OS for pts receiving 1L palbo as reported in the PALOMA-2 trial (14.6 mo vs 53.9 mo). Early progression on CDK4/6i is associated with more aggressive disease which may respond more favorably to chemotherapy, as demonstrated by best response to therapy. Further prospective studies are warranted to explore this treatment approach.

Citation Format: Katherine K. Clifton, Shana N. Thomas, Jingqin Luo, Jing Xi, Nusayba A. Bagegni, Foluso O. Ademuyiwa, Rama Suresh, Ashley Frith, Andrew A. Davis, Ron Bose, Katherine Weilbaecher, Whitney L. Hensing, Timothy Pluard, Massimo Cristofanilli, Hyo S. Han, Adam M. Brufsky, Kevin Kalinsky, Shom Goel, Seth A. Wander, Lindsay L. Peterson, Cynthia Ma. PD13-09 Clinical outcomes of patients with HR+ HER2- advanced breast cancer with early progression on CDK4/6 inhibitors [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD13-09.

Abstract OT1-03-01: XMT-1660: A Phase 1b trial of a B7-H4 targeted Antibody Drug Conjugate (ADC) in Breast, Endometrial, and Ovarian Cancers

Background: Breast cancer (BC) is the most commonly diagnosed cancer and one of the leading causes of cancer death in women. Despite significant therapeutic advances, the majority of patients with unresectable or recurrent/metastatic disease eventually develop resistance to available standard of care (SOC) therapies. B7-H4 is a poor prognostic factor and is overexpressed in several cancers including endometrial, ovarian, and breast. As a member of the CD28/B7 family of cell surface proteins, it promotes tumorigenesis by suppressing anti-tumor immunity. XMT-1660 is a B7-H4-targeted Dolasynthen antibody drug conjugate with a precise, optimized drug-to-antibody ratio and a DolaLock microtubule inhibitor payload with controlled bystander effect. In the preclinical setting, XMT-1660 has demonstrated anti-tumor activity in TNBC and ER+/HER2- patient-derived xenograft mouse models, which included tumors from heavily pre-treated patients (Collins et al, AACR 2022). Increased anti-tumor activity tended to be more frequent in models with higher B7-H4 expression, providing rationale for a Ph1 clinical trial. Methods: The Ph1 trial includes a first-in-human open-label dose escalation (DES) portion followed by dose expansion (EXP) evaluating XMT-1660 in patients with BC, EC, and OC following progression on SOC as applicable (i.e., CDK4/6i + ET; platinum-based chemotherapy). In the DES, Bayesian Optimal Interval (BOIN) design will be used to determine the MTD. Patients will receive XMT-1660 IV Q3 weeks. Primary endpoints in DES are to assess safety and determine a recommended phase 2 dose (RP2D) and assessment of preliminary efficacy as a secondary endpoint. In the EXP portion, cohorts enrolling TNBC, ER+/HER2- BC, EC/OC are planned and additional patients may be enrolled based on emerging data. The primary endpoint of EXP is to assess safety and tolerability, overall response rate, disease control rate, and duration of response. Secondary endpoints include pharmacokinetic analysis and antidrug antibodies. Patients are not selected by B7-H4 status, but baseline tumors samples are collected for retrospective tumor tissue evaluation. The trial is currently enrolling patients. NCT05377996

Citation Format: Erika Hamilton, Arvind Chaudhry, Alexander I. Spira, Sylvia Adams, Nour Abuhadra, Antonio Giordano, Ritesh Parajuli, Hyo S. Han, Amy Weise, Aubri Marchesani, Kate Josephs, Chu Ri Shin, Kevin Kalinsky. XMT-1660: A Phase 1b trial of a B7-H4 targeted Antibody Drug Conjugate (ADC) in Breast, Endometrial, and Ovarian Cancers [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT1-03-01.

Abstract P6-05-06: Patient-reported anxiety and fatigue in women enrolled in the RxPONDER trial (SWOG S1007) by menopausal status

Introduction: Anxiety and fatigue have been reported by women undergoing cytotoxic and endocrine treatment (tx) for breast cancer and can have lasting effects on quality of life (QoL). The differential effects of menopausal (meno) status, tx allocation and duration of symptoms are not well established.

Methods: Participants (pts) with hormone receptor positive, HER2 negative breast cancer with 1-3 positive lymph nodes and an Oncotype DX recurrence score of 0-25 enrolled in the RxPONDER trial were randomly assigned to endocrine therapy (ET) alone vs chemotherapy followed by ET (CET). A subset of English speaking pts in the US at the start of the trial were invited to complete health-related QoL (HRQoL) questionnaires shortly after randomization (baseline; BL) and 6, 12, and 36 months after BL until accrual goal reached. BL surveys were completed in clinic; cognitive function results presented separately. Standardized T scores (mean 50; SD 10) were computed for anxiety (PROMIS Emotional Distress – Anxiety Short Form 7a) and fatigue (PROMIS Fatigue Short Form 7a). Higher T scores indicate more anxiety or fatigue. The primary endpoint of this exploratory analysis was to compare mean anxiety and fatigue T score by tx arm by meno status. Separately by meno status, a GEE model was fit to the three follow-up timepoints adjusting for BL to estimate the difference between tx arms and whether there was a time trend over the three follow-up measures.

Results: The accrual exceeded the goal of 500 pts with 74% of pts participating voluntarily until the QOL invitation was removed from the protocol (12/1/12). A total of 139 pre and 432 postmenopausal pts completed the anxiety questionnaire at BL. There was no difference in anxiety between tx arms [Table 1]. Mean anxiety score difference between CET and ET over time in the premenopausal cohort was -0.63 (p=0.63) and in the postmenopausal cohort was 0.59 (p=0.45). Although anxiety scores decreased over the three follow-up times, the change was not statistically significant.

A total of 139 pre and 429 postmenopausal pts completed the fatigue questionnaire at BL. Fatigue mean T scores in both the pre and postmenopausal cohorts were higher over time in the CET vs ET arm [Table 2]. Fatigue scores were 2.85 points higher for CET vs. ET over time in the premenopausal cohort (p=0.02) and 1.82 points higher in the postmenopausal cohort (p=0.007). Fatigue scores decreased over time for premenopausal (p=0.01), but not for postmenopausal (p=0.62) pts.

Dropoff occurred over time with 79%, 76%, 60% of pts at BL participating at 6, 12, and 36 months. Endocrine treatment adherence data are not yet available at each timepoint.

Conclusions: CET had a clinically significant negative effect on mean fatigue scores compared to ET alone in both pre and postmenopausal pts over time. Scores improved over time but did not return to BL. Pts had lower mean anxiety scores during tx compared to BL, but differences in scores between CET and ET groups out to 3 years did not significantly differ. Future therapeutic studies must continue to include HRQoL assessments to broaden our understanding of the full impact of chemotherapy and for the development of preventative and therapeutic strategies to manage these toxicities.

Table 1. Comparisons of mean Anxiety score by treatment arm and menopausal status.

Table 2. Comparisons of mean Fatigue score by treatment arm and menopausal status.

Citation Format: Michelle M. Loch, Jamie K. Forschmiedt, Irene M. Kang, Julie R. Gralow, Funda Meric-Bernstam, Kathy S. Albain, Daniel F. Hayes, Nancy U. Lin, Edith A. Perez, Lori J. Goldstein, Priya Rastogi, Anne F. Schott, Steven Shak, Priyanka Sharma, Danika L. Lew, Jieling Miao, William E. Barlow, Debu Tripathy, Lajos Pusztai, Gabriel N. Hortobagyi, Kevin Kalinsky, N. Lynn Henry. Patient-reported anxiety and fatigue in women enrolled in the RxPONDER trial (SWOG S1007) by menopausal status [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 P6-05-06.

Phase Ib study of talimogene laherparepvec in combination with atezolizumab in patients with triple negative breast cancer and colorectal cancer with liver metastases

BACKGROUND

Talimogene laherparepvec (T-VEC), a first-in-class oncolytic viral immunotherapy, enhances tumor-specific immune activation. T-VEC combined with atezolizumab, which blocks inhibitor T-cell checkpoints, could provide greater benefit than either agent alone. Safety/efficacy of the combination was explored in patients with triple negative breast cancer (TNBC) or colorectal cancer (CRC) with liver metastases.

METHODS

In this phase Ib, multicenter, open-label, parallel cohort study of adults with TNBC or CRC with liver metastases, T-VEC (10⁶ then 10⁸ PFU/ml; ≤4 ml) was administered into hepatic lesions via image-guided injection every 21 (±3) days. Atezolizumab 1200 mg was given on day 1 and every 21 (±3) days thereafter. Treatment continued until patients experienced dose-limiting toxicity (DLT), had complete response, progressive disease, needed alternative anticancer treatment, or withdrew due to an adverse event (AE). The primary endpoint was DLT incidence, and secondary endpoints included efficacy and AEs.

RESULTS

Between 19 March 2018 and 6 November 2020, 11 patients with TNBC were enrolled (safety analysis set: n = 10); between 19 March 2018 and 16 October 2019, 25 patients with CRC were enrolled (safety analysis set: n = 24). For the 5 patients in the TNBC DLT analysis set, no patient had DLT; for the 18 patients in the CRC DLT analysis set, 3 (17%) had DLT, all serious AEs. AEs were reported by 9 (90%) TNBC and 23 (96%) CRC patients, the majority with grade ≥3 [TNBC, 7 (70%); CRC, 13 (54%)], and 1 was fatal [CRC, 1 (4%)]. Evidence of efficacy was limited. Overall response rate was 10% (95% confidence interval 0.3-44.5) for TNBC; one (10%) patient had a partial response. For CRC, no patients had a response; 14 (58%) were unassessable.

CONCLUSIONS

The safety profile reflected known risks with T-VEC including risks of intrahepatic injection; no unexpected safety findings from addition of atezolizumab to T-VEC were observed. Limited evidence of antitumor activity was observed.

Network-based assessment of HDAC6 activity predicts preclinical and clinical responses to the HDAC6 inhibitor ricolinostat in breast cancer

Inhibiting individual histone deacetylase (HDAC) is emerging as well-tolerated anticancer strategy compared with pan-HDAC inhibitors. Through preclinical studies, we demonstrated that the sensitivity to the leading HDAC6 inhibitor (HDAC6i) ricolinstat can be predicted by a computational network-based algorithm (HDAC6 score). Analysis of ~3,000 human breast cancers (BCs) showed that ~30% of them could benefice from HDAC6i therapy. Thus, we designed a phase 1b dose-escalation clinical trial to evaluate the activity of ricolinostat plus nab-paclitaxel in patients with metastatic BC (MBC) (NCT02632071). Study results showed that the two agents can be safely combined, that clinical activity is identified in patients with HR⁺/HER2^- disease and that the HDAC6 score has potential as predictive biomarker. Analysis of other tumor types also identified multiple cohorts with predicted sensitivity to HDAC6i's. Mechanistically, we have linked the anticancer activity of HDAC6i's to their ability to induce c-Myc hyperacetylation (ac-K148) promoting its proteasome-mediated degradation in sensitive cancer cells.

Proteolytic regulation of CD73 by TRIM21 orchestrates tumor immunogenicity

Despite the rapid utilization of immunotherapy, emerging challenges to the current immune checkpoint blockade need to be resolved. Here, we report that elevation of CD73 levels due to its aberrant turnover is correlated with poor prognosis in immune-cold triple-negative breast cancers (TNBCs). We have identified TRIM21 as an E3 ligase that governs CD73 destruction. Disruption of TRIM21 stabilizes CD73 that in turn enhances CD73-catalyzed production of adenosine, resulting in the suppression of CD8+ T cell function. Replacement of lysine 133, 208, 262, and 321 residues by arginine on CD73 attenuated CD73 ubiquitylation and degradation. Diminishing of CD73 ubiquitylation remarkably promotes tumor growth and impedes antitumor immunity. In addition, a TRIM21high/CD73low signature in a subgroup of human breast malignancies was associated with a favorable immune profile. Collectively, our findings uncover a mechanism that governs CD73 proteolysis and point to a new therapeutic strategy by modulating CD73 ubiquitylation.

A Tale of 3 Tracers: Contrasting Uptake Patterns of 18F-Fluciclovine, 68Ga-PSMA, and 18F-FDG in the Uterus and Adnexa

ABSTRACT

A 41-year-old woman with invasive lobular carcinoma of the breast underwent sequential 68Ga-PSMA-11 PET/CT and 18F-fluciclovine PET/CT as part of an ongoing clinical trial (NCT04750473). 68Ga-PSMA PET/CT showed increased radiotracer uptake in the uterine endometrium and left adnexa. 18F-fluciclovine PET/CT showed increased radiotracer uptake in a leiomyomatous uterus. A clinical 18F-FDG PET/CT demonstrated radiotracer uptake in the endometrium and a circumferential area of uptake in the left adnexa, a pattern more similar to the 68Ga-PSMA uptake pattern. This case highlights the discordance in the uptake pattern of 2 radiotracers approved for prostate cancer imaging but increasingly used in non-prostate malignancies imaging.

Racial Disparities in Clinical Outcomes on Investigator-Initiated Breast Cancer Clinical Trials at an Urban Medical Center

BACKGROUND

Black women are 40% more likely to die of breast cancer compared to White women. Inadequate representation of Black patients in clinical trials may contribute to health care inequity. We aimed to assess breast cancer clinical outcomes in Non-Hispanic Black (Black) versus Non-Hispanic White (White) women with metastatic breast cancer (MBC) enrolled on investigator-initiated clinical trials at Winship Cancer Institute at Emory University, given the significant number of patients from underrepresented minority groups seen at Winship.

MATERIALS AND METHODS

Black and White women with MBC on investigator-initiated trials at Emory between 2009 and 2019 were retrospectively evaluated. Univariate analyses and multiple logistic regression models were used to assess clinical response and treatment toxicities. Differences in overall survival between groups was assessed using quantile analysis.

RESULTS

Sixty-two women with MBC were included (66% White vs. 34% Black). Black patients had less clinical benefit from the trial therapy as only 57% had partial response or stable disease as best response compared to 78% of White women (P = .09). Quantile analysis showed significant difference in mean survival between Whites and Blacks by the end of follow up (64 vs. 38 months). There were no significant differences in toxicities between groups.

CONCLUSION

Participation rates of Black women with MBC on investigator-initiated clinical trials at an urban cancer center were higher compared to key national trials. Black women had worse treatment response and survival. These results reinforce the need for assessment of tumor differences by ancestry and continued improvement in minority representation on clinical trials.

Trop-2 as a Therapeutic Target in Breast Cancer

The emergence of Trop-2 as a therapeutic target has given rise to new treatment paradigms for the treatment of patients with advanced and metastatic breast cancer. Trop-2 is most highly expressed in triple negative breast cancer (TNBC), but the receptor is found across all breast cancer subtypes. With sacituzumab govitecan, the first FDA-approved, Trop-2 inhibitor, providing a survival benefit in patients with both metastatic TNBC and hormone receptor positive breast cancer, additional Trop-2 directed therapies are under investigation. Ongoing studies of combination regimens with immunotherapy, PARP inhibitors, and other targeted agents aim to further harness the effect of Trop-2 inhibition. Current investigations are also underway in the neoadjuvant and adjuvant setting to evaluate the therapeutic benefit of Trop-2 inhibition in patients with early stage disease. This review highlights the significant impact the discovery Trop-2 has had on our patients with heavily pretreated breast cancer, for whom few treatment options exist, and the future direction of novel Trop-2 targeted therapies.

Molecular differences between younger versus older ER-positive and HER2-negative breast cancers

The RxPONDER and TAILORx trials demonstrated benefit from adjuvant chemotherapy in patients age ≤ 50 with node-positive breast cancer and Recurrence Score (RS) 0-26, and in node-negative disease with RS 16-25, respectively, but no benefit in older women with the same clinical features. We analyzed transcriptomic and genomic data of ER+/HER2- breast cancers with in silico RS < 26 from TCGA (n = 530), two microarray cohorts (A: n = 865; B: n = 609), the METABRIC (n = 867), and the SCAN-B (n = 1636) datasets. There was no difference in proliferation-related gene expression between age groups. Older patients had higher mutation burden and more frequent ESR1 copy number gain, but lower frequency of GATA3 mutations. Younger patients had higher rate of ESR1 copy number loss. In all datasets, younger patients had significantly lower mRNA expression of ESR1 and ER-associated genes, and higher expression of immune-related genes. The ER- and immune-related gene signatures showed negative correlation and defined three subpopulations in younger women: immune-high/ER-low, immune-intermediate/ER-intermediate, and immune-low/ER-intermediate. We hypothesize that in immune-high cancers, the cytotoxic effect of chemotherapy may drive the benefit, whereas in immune-low/ER-intermediate cancers chemotherapy induced ovarian suppression may play important role.

Study Protocol: Efficacy and Safety of Radioembolization (REM) as an Early Modality (EM) Therapy for Metastatic Breast Cancer (BR) to the Liver with Y90 (REMEMBR Y90)

PURPOSE

The primary objective of the REMEMBR Y90 study is to evaluate the efficacy of Yttrium-90 (Y90) radioembolization in patients with breast cancer metastases to the liver as a 2nd or 3rd line treatment option with systemic therapy by assessing liver-specific and overall progression-free survival. Secondary objectives include quality of life, overall survival benefit, and toxicity in relation to patients' tumor biology.

MATERIALS AND METHODS

This trial is a multi-center, prospective, Phase 2, open-label, IRB-approved, randomized control trial in the final phases of activation. Eligible patients include those over 18 years of age with metastatic breast cancer to the liver with liver-only or liver-dominant disease, and history of tumor progression on 1-2 lines of chemotherapy. 60 patients will be randomized to radioembolization with chemotherapy versus chemotherapy alone. Permissible regimens include capecitabine, eribulin, vinorelbine, and gemcitabine within 2 weeks of enrollment for every patient. Patients receiving radioembolization will receive lobar or segmental treatment within 1-6 weeks of enrollment depending on their lesion. After final radioembolization, patients will receive clinical and imaging follow-up every 12-16 weeks for two years, including contrast-enhanced computed tomography or magnetic resonance imaging of the abdomen and whole-body positron emission tomography/computed tomography.

DISCUSSION

This study seeks to elucidate the clinical benefit and toxicity of Y90 in patients with metastatic breast cancer to the liver who are receiving minimal chemotherapy. Given previous data, it is anticipated that the use of Y90 and chemotherapy earlier in the metastatic disease course would improve survival outcomes and reduce toxicity.

LEVEL OF EVIDENCE

Level 1b, Randomized Controlled Trial.

TRIAL REGISTRATION NUMBER

NCT05315687 on clinicaltrials.gov.

Biomarkers for Systemic Therapy in Metastatic Breast Cancer: ASCO Guideline Update

PURPOSE

To update the ASCO biomarkers to guide systemic therapy for metastatic breast cancer (MBC) guideline.

METHODS

An Expert Panel conducted a systematic review to identify randomized clinical trials and prospective-retrospective studies from January 2015 to January 2022.

RESULTS

The search identified 19 studies informing the evidence base.

RECOMMENDATIONS

Candidates for a regimen with a phosphatidylinositol 3-kinase inhibitor and hormonal therapy should undergo testing for PIK3CA mutations using next-generation sequencing of tumor tissue or circulating tumor DNA (ctDNA) in plasma to determine eligibility for alpelisib plus fulvestrant. If no mutation is found in ctDNA, testing in tumor tissue, if available, should be used. Patients who are candidates for poly (ADP-ribose) polymerase (PARP) inhibitor therapy should undergo testing for germline BRCA1 and BRCA2 pathogenic or likely pathogenic mutations to determine eligibility for a PARP inhibitor. There is insufficient evidence for or against testing for a germline PALB2 pathogenic variant to determine eligibility for PARP inhibitor therapy in the metastatic setting. Candidates for immune checkpoint inhibitor therapy should undergo testing for expression of programmed cell death ligand-1 in the tumor and immune cells to determine eligibility for treatment with pembrolizumab plus chemotherapy. Candidates for an immune checkpoint inhibitor should also undergo testing for deficient mismatch repair/microsatellite instability-high to determine eligibility for dostarlimab-gxly or pembrolizumab, as well as testing for tumor mutational burden. Clinicians may test for NTRK fusions to determine eligibility for TRK inhibitors. There are insufficient data to recommend routine testing of tumors for ESR1 mutations, for homologous recombination deficiency, or for TROP2 expression to guide MBC therapy selection. There are insufficient data to recommend routine use of ctDNA or circulating tumor cells to monitor response to therapy among patients with MBC.Additional information can be found at www.asco.org/breast-cancer-guidelines.