Abstract P5-16-15: Post-progression therapy outcomes in patients (pts) from the phase 3 ASCENT study of sacituzumab govitecan (SG) in metastatic triple-negative breast cancer (mTNBC)

Abstract

Abstract Background: SG is an antibody-drug conjugate composed of an anti-Trop-2 antibody coupled to the cytotoxic SN-38 payload via a proprietary, hydrolyzable linker. SG is FDA approved for pts with mTNBC who received ≥2 prior chemotherapies (≥1 in the metastatic setting). The confirmatory phase 3 ASCENT study (NCT02574455) in pts treated in second line or greater (2L+) mTNBC demonstrated significant progression-free survival (PFS) and overall survival (OS) benefit of SG over single-agent chemotherapy treatment of physician’s choice (median PFS: 4.8 vs 1.7 months, HR 0.43, P<0.001; median OS: 11.8 vs 6.9 months, HR 0.51) in the full trial population, with a manageable safety profile. However, outcomes and patterns of subsequent therapy for pts who discontinue SG following progressive disease (PD) are not well characterized. This post hoc subgroup analysis investigates post-progression treatment and OS of pts who discontinued SG due to PD during the ASCENT trial. Methods: In ASCENT, pts with mTNBC refractory/relapsing after ≥2 prior chemotherapies (≥1 in the metastatic setting) were randomized 1:1 to receive SG (10 mg/kg IV on d 1 and 8, every 21 d) or TPC (capecitabine, eribulin, vinorelbine, or gemcitabine) until unacceptable toxicity or progression. Post-progression outcomes were assessed in pts who discontinued SG due to progressive disease (PD). Pts were followed every 4 weeks for OS, including documentation of further therapy for breast cancer. Time to post-progression therapy was defined as the number of months from time of randomization until the initiation of subsequent anticancer therapy. OS was analyzed in pts who received post-progression therapy vs those who did not and defined as the number of months from randomization or from end of SG treatment, using Kaplan Meier estimates and Cox regression. Results: 222/267 (83%) pts who were randomized to receive SG discontinued SG due to PD. In these patients median age was 53 years (range, 27-82), median number of prior anticancer regimens was 4, and 7% had known germline BRCA1/2 mutations. Pts received SG for a median duration of 4.2 months (range, 0.0-18.7). Following SG discontinuation, post-progression therapy was received by 73% (n=163) of pts; common post-SG therapies included eribulin (n=70; 32%), carboplatin (n=34; 15%), capecitabine (n=34; 15%), and atezolizumab, (n=15; 7%). The median time to receipt of post-progression therapy was 5.4 months (range, 1.0-19.8). Median OS in pts who received any post PD treatment vs those who did not receive post PD treatment following SG was 13.4 vs 7.3 months (HR, 0.46; 95% CI, 0.32-0.67; P<0.0001) from time of randomization and 7.9 vs 2.0 months (HR, 0.14; 95% CI, 0.09-0.22; P<0.0001) from end of SG treatment, respectively. In pts who received eribulin, carboplatin, atezolizumab, or capecitabine, median OS was 14.1 (95% CI, 10.9-14.9), 13.6 (95% CI, 10.6-15.9), 16.5 (95% CI, 8.7 to not evaluable), and 14.9 (95% CI, 10.9-16.8) months from time of randomization and 8.4 (95% CI, 6.8-9.2), 8.9 (95% CI, 6.7-10.8), 8.6 (95% CI, 4.3 to not evaluable), and 8.9 (95% CI, 6.6-10.3) months from end of SG treatment, respectively. Conclusions: In ASCENT, the majority of pts who discontinued SG due to PD were able to receive subsequent therapy post-progression. Pts who received post PD therapy following SG had significantly improved median OS over those who did not receive further therapy. Pts who received eribulin, carboplatin, atezolizumab, or capecitabine, as post PD therapy had similar median OS. These results indicate that treatment with SG does not prevent receipt of further systemic therapy. Citation Format: Javier Cortés, Aditya Bardia, Delphine Loirat, Sara M. Tolaney, Kevin Punie, Mafalda Oliveira, Sara A. Hurvitz, Adam Brufsky, Sagar Sardesai, Kevin M Kalinsky, Tiffany Traina, Erika Hamilton, Joyce O’Shaughnessy, Véronique Diéras, Lisa A. Carey, Martine Piccart, Sibylle Loibl, Hope S. Rugo, Yanni Zhu, See Phan, Luca Gianni. Post-progression therapy outcomes in patients (pts) from the phase 3 ASCENT study of sacituzumab govitecan (SG) in metastatic triple-negative breast cancer (mTNBC) [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-16-15.