Abstract PS02-02: Patient-reported outcomes from the Phase 3 CAPItello-291 trial investigating capivasertib and fulvestrant for patients with aromatase inhibitor-resistant HR-positive/HER2-negative advanced breast cancer

Abstract Background: In the Phase 3 CAPItello-291 trial, adding capivasertib (C), a pan-AKT inhibitor, to fulvestrant (F) in patients (pts) with aromatase inhibitor-resistant, HR+/HER2− (HER2− defined as IHC 0, or 1+ or IHC2+/ISH–) advanced breast cancer significantly improved PFS vs placebo (P) + F in the overall (HR 0.60, 95% CI 0.51, 0.71, p< 0.001) and AKT pathway-altered populations (HR 0.50, 95% CI 0.38, 0.65, p< 0.001). The safety profile of C-F was manageable; diarrhea (mostly grade 1) was the most frequent adverse event. Global health status (GHS)/health-related quality of life (HRQoL) was maintained from baseline in both arms; time to deterioration (TTD) favored C-F. We report results from additional patient-reported outcomes (PRO). Methods: Pts were randomized 1:1 to receive F (500 mg IM on days 1 and 15 of cycle 1 and day 1 of each subsequent 28-day cycle) with either P or C (400 mg BID; 4 days on, 3 days off). PRO measures assessed HRQoL, disease-related symptoms, functioning, and patient-reported treatment tolerability using the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC QLQ-C30), EORTC QLQ Breast Cancer 23 items (EORTC QLQ-BR23), PRO version of the Common Terminology Criteria for Adverse Events (PRO-CTCAE), and Patient Global Impression of Treatment Tolerability (PGI-TT). PROs were assessed at pre-specified timepoints. Change from baseline was assessed using Mixed Model Repeat Measures (on-treatment scores) for EORTC QLQ-C30 and summarized for EORTC QLQ-BR23; TTD was assessed using the stratified log-rank test for both. Results: Overall, 708 pts were randomized to C-F (n=355) or P-F (n=353). Overall compliance rates with EORTC QLQ-C30 and PGI-TT were 84.5% and 80.6% with C-F and 81.8% and 81.7% with P-F, respectively. Baseline compliance rates with the EORTC QLQ-C30 and PGI-TT were 88.2% and 82.8% with C-F and 87.3% and 83.1% with P-F, respectively. Mean changes from baseline in EORTC QLQ-C30 functional and symptom domain scores were maintained with C-F and P-F, except for diarrhea in the C-F arm, where scores worsened by >10 points (table). TTD analysis showed that HRs favored C-F vs P-F for all functional and symptom domains, except diarrhea (HR 2.75; 95% CI 2.01, 3.81), which favored P-F (table). Median TTD of diarrhea was shorter with C-F vs P-F in line with the C-F safety profile. Diarrhea with C-F was generally manageable, and discontinuations due to diarrhea were low (2.0%; n=7/355). For PGI-TT, most pts reported that they were ‘not at all’ or ‘a little bit’ bothered by the side effects of cancer therapy. Over the first 6 months, the proportion of pts reporting to be ‘somewhat’, ‘quite a bit’, or ‘very much’ bothered by side effects was higher for C-F vs P-F, with between-arm differences being highest in the first 2 cycles. Results from EORTC QLQ-BR23 domains will be presented at the meeting. Conclusions: Pts treated with C-F maintained HRQoL for longer than pts treated with P-F on all EORTC QLQ-C30 functional and symptom domain scores, except diarrhea. Worsening of diarrhea was observed with C-F, consistent with the safety profile of C, but events appeared tolerable and did not negatively impact GHS/HRQoL. Together with the clinical efficacy and manageable safety profile of C-F, the PRO results from the CAPItello-291 trial further support a positive benefit–risk profile of the combination in this population. https://clinicaltrials.gov/: NCT04305496. Funding: CAPItello-291 is sponsored by AstraZeneca. Editorial acknowledgment: AstraZeneca-funded medical writing support was provided by Suzanne Patel, Ph.D., from BOLDSCIENCE Inc. Capivasertib was discovered by AstraZeneca subsequent to a collaboration with Astex Therapeutics (and its collaboration with the Institute of Cancer Research and Cancer Research Technology Limited). Citation Format: Hope Rugo, Mafalda Oliveira, Sacha Howell, Florence Dalenc, Javier Cortés, Henry Gómez, Xichun Hu, Komal Jhaveri, Petr Krivorotko, Sibylle Loibl, Serafin Morales Murillo, Meena Okera, Yeon Park, Joo Hyuk Sohn, Eriko Tokunaga, Masakazu Toi, Samih Yousef, Lyudmila Zhukova, Marta Fulford, Haylee Andrews, Ian Wadsworth, Celina D’Cruz, Nicholas Turner. Patient-reported outcomes from the Phase 3 CAPItello-291 trial investigating capivasertib and fulvestrant for patients with aromatase inhibitor-resistant HR-positive/HER2-negative advanced 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 PS02-02.