HER2-negative Metastatic Breast Cancer Research Articles

Stromal tumor infiltrating lymphocytes in hormone receptor positive/HER2 negative metastatic breast cancer

The immune landscape of hormone receptor positive, HER2-negative metastatic breast cancer (HR+/HER2- mBC), the most common subtype of BC, remains understudied. This is mainly due to reduced sample acquisition opportunities from metastases as compared to primary tumors. In this study, we explored stromal tumor-infiltrating lymphocytes (sTIL) in metastatic samples collected through our post-mortem tissue donation program UPTIDER (NCT04531696). sTIL were scored as a continuous parameter according to international guidelines on 427 metastases and 38 primary untreated tumors acquired from 20 patients with HR+/HER2- mBC. ER-status was evaluated on 362 metastases with a cut-off for positivity set at 1% according to ASCO/CAP guidelines. Our analyses show that 54% and 15% of metastases had sTIL levels >1% and >5% respectively. sTIL levels tended to be lower in metastases as compared to their respective primary tumor (Estimate: -2.83, 95%CI: -5.77-0.11, p:0.07). sTIL levels were lower in metastases from invasive lobular carcinoma than in metastases from invasive breast carcinoma of no special type (Estimate: -1.67, 95%CI: -2.35--0.98, p:<0.001). A loss of ER expression was observed in 14% of all metastases, yet a negative ER-status was not significantly associated with increased sTIL levels. Finally, sTIL levels were significantly higher in lung and axillary lymph node metastases compared to all metastases. While these analyses were conducted on multiple metastases obtained at the end of life after several lines of treatment, the data provides novel and valuable insights into the state of immune infiltration in patients with metastatic HR+/HER2- BC.

Disparities in receipt of 1-st line CDK4/6 inhibitors with endocrine therapy for treatment of hormone receptor positive, HER2 negative metastatic breast cancer in the real-world setting

ObjectiveThis study used real-world observational data to compare profiles of patients receiving different first-line treatment for hormone receptor positive (ER+), HER2 negative, metastatic breast cancer (MBC): CDK4/6 inhibitors (CDK4/6i) in combination with endocrine therapy (ET) versus ET alone.MethodFrom a nationwide electronic health record-derived Flatiron Health de-identified database including 280 US cancer clinics, we identified patients with hormone receptor positive, HER2 negative, metastatic breast cancer receiving 1st -line therapy with ET alone or CDK4/6i plus ET between February 2015 and November 2021. Patient sociodemographic status, MBC treatment regimen and outcomes were the focus of this analysis. Patient characteristics were compared using t-tests and chi-square tests. Logistic regression analysis was performed to examine the association of patient characteristics with the likelihood of receiving 1st -line CDK4/6i plus ET vs. ET alone. Kaplan-Meier method and Cox proportional hazards were used to test the impact of 1st -line treatment regimen on real-world progression-free survival (PFS) and overall survival (OS). Baseline characteristics were balanced using inverse probability weighting (IPW).ResultsThe study population included 3,917 patients receiving CDK4/6i plus ET (n = 2170) and ET alone (n = 1747) for their MBC. Compared to patients receiving ET alone, those receiving CDK4/6i plus ET were younger (mean age 66.8 vs. 68.6, p < 0.001), more likely to present with de novo MBC (p < 0.001), had better performance status (50.2% vs. 40.5% patients with ECOG value 0, p = 0.001) and lower number of comorbidities (29.7% vs. 26.6% ≥ 1 comorbidity, p < 0.001). Logistic regression revealed increased odds of CDK4/6i plus ET in individuals aged 50–64 (OR: 3.42, 95% CI [2.41, 4.86]) and 65–74 (OR: 3.18, 95% CI [1.68, 6.02]) versus those aged 18–49 years of age. Black individuals had lower odds of CDK4/6i plus ET (OR: 0.76, 95% CI [0.58, 1.00]) compared to White individuals. Other characteristics associated with lower odds of CDK4/6i plus ET included patients with stage III disease (OR: 0.69, 95% CI [0.52, 0.92]), lower performance status (OR: 0.50, 95% CI [0.40, 0.62]), and Medicare insurance (OR: 0.73, 95% CI [0.30, 1.78]) compared to those with commercial and Medicaid insurance. After IPW adjustment, use of CDK4/6i plus ET as 1st -line treatment was associated with significantly longer median PFS compared to ET alone (27 vs. 17 months; hazard ratio [HR] = 0.61, p < 0.001). Median OS was 52 months in the CDK4/6i plus ET group and was 42 months with ET alone (HR = 0.74, p < 0.001).ConclusionIn this real-world database, disparities in receiving 1st -line CDK4/6 inhibitors were seen by age, diagnosis stage, baseline performance status, comorbidity, and insurance status. In adjusted analysis, the use of 1st -line CDK4/6i plus ET yielded better PFS and OS rates than ET alone. Further efforts are essential to enhance equitable use of and access to this crucial drug class.

Eribulin plus carboplatin combination for HER2-negative metastatic breast cancer: a multicenter, real-world cohort study

BackgroundPre-clinical data suggests a potential synergistic effect of eribulin and platinum. However, clinical data on the combination for metastatic breast cancer (mBC) is lacking. We evaluated the efficacy and safety of eribulin plus carboplatin (ErCb) in patients with mBC.Patients and methodsThis multicenter, real-world cohort study included patients with pre-treated metastatic triple negative breast cancer (TNBC) or endocrine-refractory hormone receptor (HR) positive, HER2-negative mBC who received ErCb. Eribulin (1.4 mg/m2) and carboplatin (target AUC = 2) were administered intravenously on day 1 and 8 of 21-day cycle. Objective response rate (ORR), disease control rate (DCR), progression-free survival (PFS), overall survival (OS), and adverse events (AEs) were evaluated.ResultsFrom March 2022 to December 2023, a cohort of 37 patients were recruited to the study. Among them, 22 patients have TNBC and 15 have HR + HER2 − mBC. Of the 22 patients with TNBC, 8 had an initial diagnosis of the HR + HER2 − subtype. The median treatment was 6 cycles (range, 2 − 8 cycles). In the full cohort, TNBC, and HR + HER2 − subgroup, the ORR were 51.4%, 54.5% and 46.7%, the DCR were 81.1%, 81.8% and 80%, and the median PFS were 5 months, 5 months, and 5.2 months, respectively. The median OS was 12.7 months in the entire cohort and 12.8 months in TNBC subgroup. The most common grade 3/4 hematological AEs were neutropenia (37.8%), leukopenia (35.1%), febrile neutropenia (10.8%), thrombocytopenia (5.4%), and anemia (2.7%). No grade 3/4 non-hematological AEs were observed.ConclusionErCb demonstrated favorable efficacy and tolerability in patients with heavily pre-treated mBC, especially TNBC. The findings of the current study warrant further investigation of the application of this combination in earlier lines of mBC treatment.

Monitoring the Response of Cyclin-Dependent Kinase 4/6 Inhibitors with Mean Corpuscular Volume.

Currently, the combination of cyclin-dependent kinase 4/6 (CDK4/6) inhibitors and endocrine therapy is a first-line treatment for hormone-receptor-positive and HER2-negative metastatic breast cancer. This study aimed to assess the impact of changes in Mean Corpuscular Volume (MCV) on predicting responses to treatment and survival in patients with hormone-receptor-positive, HER2-negative metastatic breast cancer receiving CDK4/6 inhibitors and endocrine therapy. Retrospectively, data on hemoglobin levels, MCV, B12, folate levels, and survival times were collected from 275 patients. Patients were categorized into two groups based on the degree of MCV change (delta MCV ≤ 10 vs. >10). Kaplan-Meier survival analysis was performed, with significance set at p < 0.05. The average age of the patients was 56.1 ± 12.1 years. In total, 72.7% received CDK4/6 inhibitors as first-line treatment, while 27.3% received them as second-line treatment. Before CDK4/6 inhibitor use, the median MCV level was 87.7 fL (IQR: 83-91), which increased to 98 fL (IQR: 92-103) after treatment (p < 0.001). ECOG performance score, CDK4/6 inhibitor treatment line, type of endocrine therapy, and MCV change were identified as independent predictors of progression-free survival in the Cox regression model. The median progression-free survival for the entire group was 28 months. Patients with MCV delta > 10 had a median progression-free survival of 33 months, compared to 23 months for those with MCV delta ≤ 10 (p = 0.029). There was no significant difference in median overall survival times between the two groups (p = 0.158). This study highlights that patients with MCV delta > 10 had longer median progression-free survival compared to those with MCV delta ≤ 10.

Canadian Expert Recommendations on Safety Overview and Toxicity Management Strategies for Sacituzumab Govitecan Based on Use in Metastatic Triple-Negative Breast Cancer.

Sacituzumab Govitecan (SG) is an antibody-drug conjugate (ADC) comprised of an anti-Trop-2 IgG1 molecule conjugated to SN-38, the active metabolite of irinotecan, via a pH-sensitive hydrolysable linker. As a result of recent Canadian funding for SG in advanced hormone receptor (HR)-positive breast cancer and triple-negative breast cancer (TNBC), experience with using SG and managing adverse events (AEs) has grown. This review presents a summary of evidence and adverse event recommendations derived from Canadian experience, with SG use in metastatic TNBC for extrapolation and guidance in all indicated settings. SG is dosed at 10 mg/kg on day 1 and day 8 of a 21-day cycle. Compared to treatment of physicians' choice (TPC) the phase III ASCENT and TROPiCS-02 studies demonstrated favorable survival data in unresectable locally advanced or metastatic TNBC and HR-positive HER2 negative metastatic breast cancer, respectively. The most common AEs were neutropenia, diarrhea, nausea, fatigue, alopecia, and anemia. This review outlines AE management recommendations for SG based on clinical trial protocols and Canadian guidelines, incorporating treatment delay, dose reductions, and the use of prophylactic and supportive medications.

The choice of optimal therapy for ER+ HER2-metastatic breast cancer (PROMETHEUS): all-Russian analysis of physicians’ preferences – updated survey results

Cyclin-dependent kinase 4/6 inhibitors (iCDK4/6) are the generally accepted standard of care for the treatment of luminal HER2-negative metastatic breast cancer (ER+HER2- mBC). Data from randomized and observational studies have proven the high effectiveness of the combination of iCDK4/6 and endocrine therapy (ET) both in the 1st and in subsequent lines. The use of new drugs in real clinical practice is determined by a number of factors, including the awareness of doctors, their personal experience and subjective preferences, as well as financial support and availability in a particular region. To assess the frequency of prescription of CDK4/6, as well as other types of treatment in the 1st‑2nd line of therapy for ER+ HER2- mBC in real clinical practice in Russia, as well as to determine the factors and preferences of doctors influencing their choice, the National Association of Oncomammologists (NAOM) conducted a survey “Prometheus” of oncology specialists. From February 15 to August 30, 2023, a web survey of healthcare professionals who treat patients with mBC was conducted on the website anketolog.ru. An invitation to survey was sent out through the NAOM database, 112 questionnaires were received and processed. Earlier, in 2020, the “Prometheus” survey was conducted on the territory of the Russian Federation for a similar purpose. In this paper, we present the results of an updated and expanded survey and evaluate changes that have occurred over the past 3 years in actual clinical practice. The results of a 2023 survey conducted in the Russian Federation on the choice of early-line therapy for ER+HER2- mBC showed that, compared with the 2020 survey, the level of “trust” in iCDK4/6 has increased among practicing physicians, and the indications for their use have expanded, including visceral metastases (and even pending visceral crisis), the indications for prescribing chemotherapy in the 1st line have narrowed. When using monoET in the 1st line, the majority of respondents prescribe iCDK4/6 in the 2nd line. Obviously, the wider use of iCDK4/6 is associated not only with the accumulation of clinical knowledge and experience in the use of drugs, but also with improved drug supply. However, the main limitations to the use of iCDK4/6 are still insufficient funding and organizational difficulties. However, it should be noted that 1/5 of the respondents do not face any restrictions and widely prescribe combination therapy.

388P Anlotinib or bevacizumab combined with chemotherapy for the second-line HER-2 negative metastatic breast cancer: A retrospective cohort study

388P Anlotinib or bevacizumab combined with chemotherapy for the second-line HER-2 negative metastatic breast cancer: A retrospective cohort study

377P Phase II study of trifluridine/tipiracil in pre-treated patients with ER-positive, HER2-negative metastatic breast cancer: A Dutch BOOG (2019-01 TIBET) study

377P Phase II study of trifluridine/tipiracil in pre-treated patients with ER-positive, HER2-negative metastatic breast cancer: A Dutch BOOG (2019-01 TIBET) study

344MO ESG401, a novel Trop2 antibody-drug conjugate (ADC), and its efficacy evidence in HER2-negative metastatic breast cancer with brain metastases

344MO ESG401, a novel Trop2 antibody-drug conjugate (ADC), and its efficacy evidence in HER2-negative metastatic breast cancer with brain metastases

357P Bridging the gap between real-world studies (RWSs) and randomized controlled trials (RCTs) of 1st-line palbociclib+aromatase inhibitors (P+AI) in hormone receptor-positive (HR+)/HER2-negative(-) metastatic breast cancer (mBC)

357P Bridging the gap between real-world studies (RWSs) and randomized controlled trials (RCTs) of 1st-line palbociclib+aromatase inhibitors (P+AI) in hormone receptor-positive (HR+)/HER2-negative(-) metastatic breast cancer (mBC)

Antibody-drug conjugates in metastatic breast cancer: sequencing, combinations and resistances.

Significant advancements have been made in treating metastatic breast cancer (MBC) with antibody drug conjugates (ADCs). However, due to the development of resistance, patients experience disease progression. The aim of this review is to summarize current evidence on ADCs sequencing strategies and combination approaches in the treatment of MBC. Concerning HER2 positive MBC, current evidence on the optimal ADC-sequencing is primarily about T-DXd, which demonstrated therapeutic value when used post-T-DM1. Conversely, data are limited about the reverse sequence. Similarly, in HER2-negative MBC, recent studies evaluated the sequential use of Sacituzumab Govitecan and T-DXd, which was associated with poor responses. Retrospective analyses have not demonstrated an optimal sequencing strategy for ADCs, and it is still very unclear whether switching the payload or targeting a different antigen may represent the best approach. Combinations may better overcome ADC resistance: interesting data associating immunotherapy or tyrosine kinase inhibitors to ADCs appear promising, albeit data are still immature. In MBC, ADCs have expanded treatment options but their sequential use requires further study. Evidence suggests that sequencing ADCs with similar payloads is ineffective, though current data are inconclusive. More research is needed to optimize treatment strategies, including potential combination therapies.

Proton pump inhibitors decrease efficacy of palbociclib in patients with metastatic breast.

The objective of this investigation was to assess the impact of concurrent proton pump inhibitors (PPIs) on progression-free survival (PFS) in patients with hormone receptor-positive and HER2-negative metastatic breast cancer (mBC) who received palbociclib as first-line or successives therapy. A retrospective observational study was conducted, enrolling patients diagnosed with estrogen receptor-positive, human epidermal growth factor receptor 2-negative mBC, and eligible for palbociclib treatment. Patients were categorized as "concurrent PPIs" if they received PPIs for at least two-thirds of the palbociclib therapy duration, and as "no concurrent PPIs" if they did not receive PPIs during the course of palbociclib treatment. A total of 165 patients were included in the study. Among first-line patients treated with palbociclib, those using concurrent PPIs exhibited a PFS of 8.88 months, while patients using palbociclib without concurrent PPIs had a PFS of 67.81 months (p < 0.0001). In second-line or subsequent treatments, patients on palbociclib with concurrent PPIs had a PFS of 7.46 months, whereas those using palbociclib without concurrent PPIs had a PFS of 17.29 months (p = 0.122). This study demonstrates that the concurrent use of PPIs in mBC patients receiving palbociclib negatively affects PFS, particularly in the first-line setting. Nevertheless, further investigation is warranted to explore the impact of PPIs on cycle-dependent kinase 4/6 inhibitors.

A Phase I Trial of Alpelisib Combined With Capecitabine in Patients With HER2-Negative Metastatic Breast Cancer

BackgroundAlpelisib is an oral α-specific class I PI3K inhibitor approved in combination with fulvestrant for the treatment of PIK3CA-mutated hormone receptor-positive (HR+), human epidermal growth factor receptor 2 negative (HER2-) metastatic breast cancer. The tolerability of this drug with the oral chemotherapy capecitabine is unknown. Patients and MethodsThis phase I trial evaluated the dose-limiting toxicities (DLTs) and maximum tolerated dose (MTD) of alpelisib (250 mg or 300 mg daily for 3-weeks) with capecitabine (1000 mg/m2 twice daily for 2-weeks followed by a 1-week rest period) in patients with metastatic HER2-negative breast cancer, regardless of PIK3CA mutation status. ResultsEighteen patients were treated with alpelisib-capecitabine. Half of the patients had HR+ breast cancer, and 16 had prior systemic therapy for metastatic disease. The MTD of alpelisib was 250 mg daily in combination with capecitabine 1000 mg/m2 twice daily. DLTs included hyperglycemia, QTc prolongation, fatigue, and chest pain. The most common grade 3 adverse event (AE) was hyperglycemia (28%). No grade 4 AEs were observed. Three patients discontinued therapy due to an AE. One-third of patients required dose reduction of both alpelisib and capecitabine. Four patients experienced a partial response and 8 patients experienced stable disease. The median progression-free survival was 9.7 months (95% CI 2.8-13.5 months) and median overall survival was 18.2 months (95% CI 7.2-35.2 months). Twelve patients had PIK3CA mutation testing completed, of these 2 had known or likely deleterious PIK3CA mutation. ConclusionThis study provides safety data for an oral combination therapy of alpelisib-capecitabine and defines tolerable doses for further study.

Eribulin versus S-1 as first or second-line chemotherapy to assess health-related quality of life and overall survival in HER2-negative metastatic breast cancer (RESQ study): a non-inferiority, randomised, controlled, open-label, phase 3 trial

Eribulin prolongs overall survival (OS) of patients with human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer (MBC), particularly in later chemotherapy (ChT) treatment. However, the health-related quality of life (HRQoL) and efficacy of first or second-line therapy in eribulin-treated patients remain unknown. Using eribulin in the first- or second-line may demonstrate the non-inferiority of HRQoL compared to S-1, an oral 5-fluorouracil derivative, while maintaining OS. This randomised, controlled, open-label, phase III trial was conducted at 50 hospitals in Japan. Patients were enrolled from June 2016 and October 2019. Patients with HER2-negative MBC once under or no previous ChT were randomly assigned (1:1) to receive eribulin or S-1. HRQoL was assessed using the European Organization for Research and Treatment of Cancer (EORTC) Quality of Life Questionnaire-Core 30 (QLQ-C30) every six weeks until week 24 and every nine weeks until week 42. The primary endpoint was the deterioration defined as more than 10 points worsening of the general health score of QLQ-C30 or death within one year after randomisation. The secondary endpoints included OS. (Trial ID: UMIN000021398). Three hundred and two patients were enrolled, with 152 and 148 assigned to the eribulin and S-1 groups, respectively. The questionnaire compliance rate was 85.6%. Risk difference of global health status deterioration through one year was-0.66% (95% CI:-12.47-11.16; non-inferiority P=0.077) for eribulin compared to S-1 groups. Median time to first deterioration for global health status score was 5.64 (95% CI: 3.51-8.00) and 5.28 months (95% CI: 3.28-7.80) in the eribulin and S-1 groups, respectively. The median OS was 34.7 and 27.8 months, (HR: 0.72, 95% CI: 0.54-0.96; P=0.026); the median progression-free survival was 7.57 and 6.75 months in the eribulin and S-1 groups, (HR: 0.88, 95% CI: 0.67-1.16; P=0.35), respectively. No new adverse events occurred. The time of the first clinical deterioration was similar between the two groups and OS significantly increased in eribulin-treated patients. This study was funded by CSPOR-BC and Eisai CO., Ltd.

Metronomic chemotherapy plus anti-PD-1 in metastatic breast cancer: a Bayesian adaptive randomized phase 2 trial.

It remains unclear whether metronomic chemotherapy is superior to conventional chemotherapy when combined with immune checkpoint blockade. Here we performed a phase 2 clinical trial of metronomic chemotherapy combined with PD-1 blockade to compare the efficacy of combined conventional chemotherapy and PD-1 blockade using Bayesian adaptive randomization and efficacy monitoring. Eligible patients had metastatic HER2-negative breast cancer and had not received more than one prior line of standard chemotherapy. Patients (total n = 97) were randomized to receive (1) metronomic vinorelbine (NVB) monotherapy (n = 11), (2) NVB plus anti-PD-1 toripalimab (n = 7), (3) anti-angiogenic bevacizumab, NVB and toripalimab (n = 27), (4) conventional cisplatin, NVB and toripalimab (n = 26), or (5) metronomic cyclophosphamide, capecitabine, NVB and toripalimab (the VEX cohort) (n = 26). The primary endpoint was disease control rate (DCR). Secondary objectives included progression-free survival (PFS) and safety. The study met the primary endpoint. The VEX (69.7%) and cisplatin (73.7%) cohorts had the highest DCR. The median PFS of patients in the VEX cohort was the longest, reaching 6.6 months, followed by the bevacizumab (4.0 months) and cisplatin (3.5 months) cohorts. In general, the five regimens were well tolerated, with nausea and neutropenia being the most common adverse events. An exploratory mass cytometry analysis indicated that metronomic VEX chemotherapy reprograms the systemic immune response. Together, the clinical and translational data of this study indicate that metronomic VEX chemotherapy combined with PD-1 blockade can be a treatment option in patients with breast cancer. ClinicalTrials.gov Identifier: NCT04389073 .

Concurrent use of Radiotherapy and Ribociclib: Preliminary Results and Review of the Literature.

In the recent MONALEESA-2, MONALEESA-3, and MONALEESA-7 clinical trials, the addition of ribociclib, a CDK4/6 inhibitor, to standard endocrine therapy significantly improved progression-free survival (PFS) compared with hormone therapy alone in the treatment of locally advanced or metastatic estrogen receptor-positive (ER) and HER2-negative breast cancer. However, its toxicity raises concerns when administered concomitantly with radiotherapy, leading most radiotherapists and medical oncologists to prefer to discontinue Ribociclib during radiotherapy (RT). Although there are insufficient published data on this combination, our preliminary experience with the first 2 patients treated at Institut Curie suggests promising results when using Ribociclib with Letrozole or Fulvestrant concurrently with palliative radiotherapy in the treatment of metastatic breast cancer. Our study aimed to evaluate the safety of combining Ribociclib with palliative radiotherapy in patients with metastatic breast cancer, providing crucial insights for clinical decision-making. A retrospective analysis was conducted on patients treated for hormone receptor-positive metastatic breast cancer with Ribociclib and concurrent radiotherapy at the Institut Curie (Paris, France) between September 2023 and April 2024. Among 38 patients who received Ribociclib and underwent irradiation, 36 temporarily suspended Ribociclib during radiotherapy, while 2 continued Ribociclib concurrently and were included in the analysis. Palliative radiotherapy was administered using volumetric modulated arc therapy, delivering 20Gy in 5 fractions to bone metastatic sites. Ribociclib was given at 600mg/day with hormonotherapy. Follow-up was conducted from the last day of RT until the last medical consultation. Toxicities were graded using CTCAE V5.0. Two patients received Ribociclib concomitantly with radiotherapy, experiencing pain relief without interruptions in RT. However, Ribociclib treatment was halted in both cases due to grade 3 neutropenia and grade 1 QTc interval prolongation, respectively. One patient had a dose reduction to 400mg due to neutropenia, with favorable outcomes observed. Both patients continued Ribociclib treatment, with one achieving complete remission and the other partial remission of bone disease. No late toxicities were observed. Despite the need for further investigation, our results suggest safety consistent with pivotal trials, advocating for a prospective cooperative data collection initiative to explore this combined strategy further, potentially revolutionizing metastatic breast cancer management.

First- vs second-line CDK 4/6 inhibitor use for patients with hormone receptor positive, human epidermal growth-factor receptor-2 negative, metastatic breast cancer in the real world setting

PurposeTo compare CDK4/6 inhibitor (CDK4/6i) with endocrine therapy (ET) in the first- versus second-line setting for treatment of hormone receptor positive (HR+), HER2 negative, metastatic breast cancer (MBC) using real-world evidence.MethodsPatients with HR+, HER2 negative MBC, diagnosed between 2/3/2015 and 11/2/2021 and having ≥ 3 months follow-up were identified from the nationwide electronic health record-derived Flatiron Health de-identified database. Treatment cohorts included: (1) first-line ET with a CDK 4/6i (1st-line CDK4/6i) versus (2) first-line ET alone followed by second-line ET with a CDK4/6i (2nd-line CDK4/6i). Differences in baseline characteristics were tested using chi-square tests and two-sample t-tests. Time to third-line therapy, time to start of chemotherapy, and overall survival were compared using Kaplan-Maier method.ResultsThe analysis included 2771 patients (2170 1st-line CDK4/6i and 601 2nd-line CDK4/6i). Patients receiving 1st-line CDK4/6i were younger (75% vs 68% < 75 years old, p = 0.0001), less likely uninsured or not having insurance status documented (10% vs. 13%, p = 0.04), of better performance status (50% vs 43% with ECOG 0, p = 0.03), and more likely to have de novo MBC (36% vs. 24%, p < 0.001). Time to third-line therapy (49 vs 22 months, p < 0.001) and time to chemotherapy (68 vs 41 months, p < 0.001) were longer in those receiving first-line CDK4/6i. Overall survival (54 vs 49 months, p = 0.33) was similar between groups.ConclusionUse of CDK4/6i with first-, vs second-, line ET was associated with longer time to receipt of 3rd-line therapy and longer time to receipt of chemotherapy.

The somatic mutation profile of estrogen receptor-positive HER2-negative metastatic breast cancer in Brazilian patients.

Breast cancer is the leading cause of cancer death among women worldwide. Studies about the genomic landscape of metastatic breast cancer (MBC) have predominantly originated from developed nations. There are still limited data on the molecular epidemiology of MBC in low- and middle-income countries. This study aims to evaluate the prevalence of mutations in the PI3K-AKT pathway and other actionable drivers in estrogen receptor (ER)+/HER2- MBC among Brazilian patients treated at a large institution representative of the nation's demographic diversity. We conducted a retrospective observational study using laboratory data (OC Precision Medicine). Our study included tumor samples from patients with ER+/HER2- MBC who underwent routine tumor testing from 2020 to 2023 and originated from several Brazilian centers within the Oncoclinicas network. Two distinct next-generation sequencing (NGS) assays were used: GS Focus (23 genes, covering PIK3CA, AKT1, ESR1, ERBB2, BRCA1, BRCA2, PALB2, TP53, but not PTEN) or GS 180 (180 genes, including PTEN, tumor mutation burden [TMB] and microsatellite instability [MSI]). Evaluation of tumor samples from 328 patients was undertaken, mostly (75.6%) with GS Focus. Of these, 69% were primary tumors, while 31% were metastatic lesions. The prevalence of mutations in the PI3K-AKT pathway was 39.3% (95% confidence interval, 33% to 43%), distributed as 37.5% in PIK3CA and 1.8% in AKT1. Stratification by age revealed a higher incidence of mutations in this pathway among patients over 50 (44.5% vs 29.1%, p=0.01). Among the PIK3CA mutations, 78% were canonical (included in the alpelisib companion diagnostic non-NGS test), while the remaining 22% were characterized as non-canonical mutations (identifiable only by NGS test). ESR1 mutations were detected in 6.1%, exhibiting a higher frequency in metastatic samples (15.1% vs 1.3%, p=0.003). Additionally, mutations in BRCA1, BRCA2, or PALB2 were identified in 3.9% of cases, while mutations in ERBB2 were found in 2.1%. No PTEN mutations were detected, nor were TMB high or MSI cases. We describe the genomic landscape of Brazilian patients with ER+/HER2- MBC, in which the somatic mutation profile is comparable to what is described in the literature globally. These data are important for developing precision medicine strategies in this scenario, as well as for health systems management and research initiatives.

Overall survival analysis of first line CDK4/6 inhibitors in a large real-world cohort of patients with hormone receptor-positive (HR+)/HER2-negative metastatic breast cancer.

e13095 Background: Multiple clinical trials have demonstrated the efficacy of the commercially available CDK4/6 inhibitors (CDK4/6i) combined with endocrine therapy (ET) as upfront therapy in patients (pts) with (HR+)/HER2-negative (HER2-) metastatic breast cancer (MBC). Recently, differences in overall survival (OS) benefit in MBC and invasive disease-free survival benefit in early-stage BC suggest greater potency of abemaciclib and ribociclib compared to palbociclib. Here we report a comprehensive OS analysis of a cohort of pts with HR+/HER2- MBC treated with ribociclib, palbociclib or abemaciclib and ET in 1st line setting. Methods: We retrieved medical records of pts with HR+/HER2- MBC receiving CDK4/6i as 1st line therapy between December 2013 and October 2023 at Memorial Sloan Kettering Cancer Center. We investigated the impact of clinico-pathological characteristics and treatment type as categorical variables on OS using uni- and multivariate Cox (proportional hazard) regression model. Any p-value (p) &lt;0.05 was deemed to be statistically significant. Results: 854 pts were included in the analysis, 838 females (98%) and 16 males at birth. The median age was 56 (IQR: 48-65). Overall, 722 (84%) pts received palbociclib, 88 (11%) abemaciclib, and 44 (5%) ribociclib. Most pts received aromatase inhibitor (AI) as ET backbone (n=634, 74%); 214 received fulvestrant (35%), and 6 received tamoxifen (1%). After a median follow-up of 3.14 years (range: 1.7-4.6), the median OS of the full cohort was 54.7 months (95%CI: 50-63.1). Clinico-pathological characteristics that resulted independently associated with worse OS were: male gender at birth (HR:2, 95%CI:1.4-4), disease-free interval ≤ 2 years (HR:1.64, 95%CI:1.11-2.44), ER-low status (HR: 2.27, 95%CI:1.42-3.63), high grade(HR: 1.28, 95%CI:1.01-1.62), liver involvement (HR: 1.48, 95%CI:1.08-2.03), and number of disease sites &gt;3 (HR:1.35, 95%CI:1.03-1.78). HER2-low status was associated with better OS (HR: 0.75, 95%CI:0.59-0.96). In terms of type of treatment, there was a trend toward improved OS in patients receiving AI rather than fulvestrant or tamoxifen (HR:0.76, 95%: 0.58-1), while the type of CDK4/6i did not affect the outcome. Conclusions: Clinical parameters of early relapse, high disease burden, and intrinsic tumor aggressiveness seem to be the main drivers of poor prognosis in patients with HR+/HER2- MBC in 1st line setting. In this analysis, type of CDK4/6i did not have a significant impact on OS, although pts treated with abemaciclib and ribociclib were underrepresented in the cohort due to the earlier and prevalent use of palbociclib as the first-in-class FDA-approved CDK4/6i. These data are reassuring about the use of palbociclib suggesting that a switch of CKD4/6i is not needed in pts with ongoing treatment and demonstrated benefit.

Genomic testing and uptake of alteration-targeted therapies among patients with hormone-receptor positive (HR+) metastatic breast cancer (MBC).

e13084 Background: There is no recognized standard of care treatment after progression on first-line endocrine therapy plus CDK4/6 inhibitor in HR+ / HER2 negative MBC. Alteration-targeted therapies (ATT) have the potential to delay initiation of chemotherapy with more favorable toxicity, and perhaps improved efficacy. Next-generation sequencing (NGS) of tumor tissue or circulating tumor DNA (ctDNA) can identify actionable mutations for targeted therapy. In this study, we sought to assess the results of genomic testing and uptake of ATT among patients with HR+ / HER2-negative MBC. Methods: We studied a retrospective cohort of patients with MBC who received treatment in the Koontz Center for Advanced Breast Cancer (KABCC) at St. Luke’s Cancer Institute, a community-based health system in the Kansas City metro area. The analytic cohort included 125 patients with HR+ / HER2-negative MBC who received treatment after progression on first-line therapy. Genomic testing was performed as a standard of care from ctDNA or tumor-tissue using commercially available NGS assays. Targetable alterations were defined as those with FDA-approved or routinely used off-label treatment regimens in MBC ( PIK3CA, PTEN, AKT, ESR1, ERBB2, BRCA1, BRCA2, PALB2 mutations; TMB &gt;10 or PDL1+). We identified patients who received any ATT and compared them with those who did not. Overall survival (OS) and time to initiation of chemotherapy (TTC) were compared between the two groups using Kaplan-Meier analyses and the log-rank test. Results: Ninety-nine patients (79.2%) had genomic testing and 49 (39.2%) were tested prior to second-line therapy. Of those tested, 84% had at least one targetable alteration. ESR1 mutations were most common, detected in 36% of patients, followed by PIK3CA (31.2%), PTEN (12%), BRCA1/2 (7.2%) and ERBB2 (5.6%). A total of 35 patients received ATT, and around half of those (17 patients) received ATT in the second line. Alpelisib was the most common ATT (62.9%), followed by elacestrant (20%) and neratinib (14.3%). There was no significant difference in OS or TTC between the two groups. Conclusions: Approximately 80% of patients with HR+ / HER2-negative MBC in our cohort underwent genomic testing after progression on first-line therapy, and the vast majority had at least one targetable alteration identified. However, only 35 patients received ATT with most receiving alpelisib. We observed no significant improvement in OS or TTC among those who received ATT, although the numbers were small. There have been two new targeted therapies approved in the past year and many novel agents are currently under investigation in clinical trials. Newer therapies with distinct targets, improved tolerability and efficacy have the potential to improve the uptake and clinical benefit of targeted therapy in MBC.