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Outcomes in patients (pts) aged ≥65 years in the phase 3 ASCENT study of sacituzumab govitecan (SG) in metastatic triple-negative breast cancer (mTNBC).

1011 Background: Approximately 20% of pts diagnosed with TNBC are aged ≥65 y. Often, older pts are less fit for chemotherapy due to a greater rate of comorbidities, increased use of medications, and pre-existing frailty or functional loss. 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. The landmark phase 3 ASCENT study (NCT02574455) showed improved outcomes with SG vs single-agent chemotherapy of physician’s choice (TPC) in pts with relapsed/refractory mTNBC (median progression-free survival [PFS], 5.6 vs 1.7 mo; median overall survival [OS], 12.1 vs 6.7 mo). Here we assess the impact of age on the efficacy and safety of SG in ASCENT. Methods: Pts with mTNBC refractory/relapsing after ≥2 prior chemotherapies were randomized 1:1 to receive SG (10 mg/kg IV on days 1 and 8, every 21 days) or TPC (capecitabine, eribulin, vinorelbine, or gemcitabine) until disease progression/unacceptable toxicity. Primary endpoint was PFS per RECIST 1.1 by independent review in brain metastases-negative (BMNeg) pts. Safety outcomes were assessed in all treated pts. This prespecified subgroup analysis assessed the impact of age (pts ≥65 y) on PFS, OS, and safety. Results: Of 529 pts enrolled, 468 were BMNeg (median age, 54 y); of these, 44/235 pts (19%) who received SG and 46/233 pts (20%) who received TPC were aged ≥65 y. SG treatment improved median PFS vs TPC in pts ≥65 y (7.1 vs 2.4 mo; HR, 0.22; 95% CI, 0.12-0.40). SG vs TPC treatment also improved median OS in pts ≥65 y (15.3 vs 8.2 mo; HR, 0.37; 95% CI, 0.22-0.64). Treatment with SG vs TPC resulted in higher ORR (50% vs 0%) and clinical benefit rate (CBR, 61% vs 9%) in pts ≥65 y. Of the 7 pts ≥75 y who received SG, 2 had partial response, 4 had stable disease [SD], and 1 had SD > 6 mo as best response. In pts < 65 y, median PFS for SG vs TPC was 4.6 vs 1.7 mo (HR, 0.46; 95% CI, 0.35-0.59), and median OS was 11.2 vs 6.6 mo (HR, 0.50; 95% CI, 0.40-0.64), respectively; the ORR and CBR were 31% vs 6% and 41% vs 9%, respectively. Pts ≥65 y treated with SG vs TPC had similar rates of all grade and grade ≥3 treatment-emergent adverse events (TEAEs). TEAEs leading to dose reduction were similar in pts ≥65 y in the SG vs TPC arms (35% vs 33%) and were lower in pts < 65 y (19% vs 24%). Key treatment-related TEAEs leading to dose reduction in pts ≥65 y in the SG vs TPC arms were neutropenia (including febrile neutropenia; 14% vs 25%), fatigue (10% vs 4%), diarrhea (6% vs 0%), and nausea (4% vs 0%). TEAEs leading to treatment discontinuation with SG vs TPC were low in pts ≥65 y (2% vs 2%) and < 65 y (5% vs 6%). There were no treatment-related AEs leading to death in any SG-treated age group. Conclusions: Irrespective of age, pts who received SG had a significant survival benefit vs TPC, with a tolerable safety profile. Proactive AE monitoring and management will allow optimal therapeutic exposure to SG in older pts. Clinical trial information: NCT02574455 .