Abstract PO2-06-07: A Randomized Phase II Comparison of Single-Agent Carboplatin versus the Combination of Carboplatin and Everolimus for the Treatment of Advanced Triple Negative Breast Cancer

Abstract

Abstract Background: Both TNBC and BRCA-1 associated breast cancers are sensitive to DNA cross-linking agents such as platinum compounds due to defective DNA repair by homologous recombination. TNBCs are also associated with a high frequency of PTEN loss, which can lead to activation of the mTOR pathway resulting in tumor cell growth and proliferation. mTOR activation can confer resistance to platinum agents, and this phenomenon may be reversible by the addition of an mTOR inhibitor, such as everolimus. A prior phase II single arm trial of carboplatin and everolimus in patients (pts) with advanced TNBC demonstrated good tolerability and preliminary efficacy. Methods: We conducted a phase II, multicenter, randomized trial in pts with advanced TNBC, who had received 0-3 prior lines of therapy. Pts were randomly assigned (in a 2:1 ratio) to carboplatin and everolimus or carboplatin alone. The primary endpoint was progression-free survival (PFS). Secondary endpoints included overall survival (OS), overall response rate (ORR), clinical benefit rate (CBR), and safety. We planned to enroll 72 pts which would provide > 80% power for a one-sided log-rank test at the 5% level of significance, to detect a 2.5 month improvement in median PFS between treatment groups, assuming a median PFS of 2.5 months in the control group. An interim analysis for futility was planned after 36 events with a stopping boundary of P <0.375 for the comparison of PFS, using an Obrien-Fleming spending function. Of note, the trial was stopped earlier than planned based on a sensitivity/tipping point analysis which indicated that terminating the trial 3 months ahead of schedule would have no substantial impact on the primary endpoint. Results: A total of 56 pts were randomized between 2015 and 2022, of whom 36 received carboplatin/everolimus and 20 carboplatin alone. The median age of the population was 62.8 years (range: 33-87) and about 20% of pts had BRCA-1 or BRCA-2 mutations. In the overall population, pts had received a median of 1 (range 1-3) prior line of therapy in the metastatic setting, with 75% of pts receiving prior chemotherapy and 47% prior carboplatin. The median PFS was significantly improved in pts who received carboplatin and everolimus (4.7 months) versus those who received carboplatin alone (2.1 months; HR: 0.37; 95% CI: 0.19-0.72; p=0.0042). Overall survival was 22.1 months in pts on the combination versus 14.4 months on carboplatin alone (HR: 0.73; 95% CI: 0.30-1.72; p=0.3106). CBR was 61% with the combination vs 50% with carboplatin monotherapy, as shown in Table 1. Most common adverse events (AEs) on carboplatin and everolimus included thrombocytopenia (81%), anemia (69%), leukopenia (67%), fluid retention (64%), and neutropenia (61%). Overall, Grade 3/4 events occurred in 75% of pts (83% of pts on combination vs 60% on carboplatin alone) and were primarily anemia (40% vs 17%), thrombocytopenia (47% vs 0%), and neutropenia (20% vs 0%). Of note, there was an increase in thrombocytopenia with the addition of everolimus (All Grades: 81% vs 35%, Grade 3/4: 39% vs 0%). Conclusions: Treatment options for TNBC are limited due to a lack of targeted therapies. The combination of carboplatin and everolimus in this study was associated with a 63% reduction in risk of progression or death in pts with metastatic TNBC. The regimen was well tolerated and provides a promising treatment option for pts with advanced TNBC. Table 1. Results in Patients on Carboplatin and Everolimus versus Carboplatin Alone NE= Not Estimable; 1Unevaluable patients treated as non-responders in CBR and ORR calculations. Citation Format: Rima Patel, Jami Fukui, Paula Klein, Erin Moshier, Charles Shapiro, Anupama Goel, Julie Fasano, Theresa Shao, Aarti Bhardwaj, Rita Vaccaro, Gargi Atul Joshi, Joseph Sparano, Amy Tiersten. A Randomized Phase II Comparison of Single-Agent Carboplatin versus the Combination of Carboplatin and Everolimus for the Treatment of Advanced Triple Negative Breast Cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-06-07.