Introduction: Approximately 40% of pts with HR+, HER2– ABC have tumors with a PIK3CA mutation, resulting in PI3K pathway hyperactivation. In SOLAR-1, the oral α-specific PI3K inhibitor alpelisib (+fulvestrant) significantly improved (vs placebo+fulvestrant) both PFS and ORR in the PIK3CA-mutant cohort. PROs offer insight into therapeutic benefit by measuring whether quality of life (QoL) is maintained during treatment.

Methods: Postmenopausal women or men with HR+, HER2– ABC whose disease progressed on/after an AI were randomized to receive alpelisib 300 mg QD (or placebo) +fulvestrant 500 mg Q28d + C1d15. Secondary objectives included PROs using EORTC QLQ-C30, EQ-5D-5L, and BPI-SF scales. PROs were collected at screening, every 8 weeks for 18 months then every 12 weeks thereafter, at end of treatment, and during follow-up for efficacy. Linear mixed effects models were used to assess score changes from baseline. Time to 10% deterioration (TTD) was compared between arms’ survival distribution per Kaplan-Meier methodology.

Results: Of pts in the PIK3CA-mutant cohort (n=341), 93% and ≥75% completed questionnaires at baseline and post-baseline, respectively. Adjusted mean changes from baseline in EORTC global health status/QoL scores were <10% for all visits through week 96 for both arms, with a mean difference between arms of <3% for all visits. There was no difference between arms in TTD in global health/QoL status (HR, 1.03; 95% CI, 0.72-1.48). Analysis of TTD in EORTC physical, social, and emotional functioning scores revealed no meaningful differences between arms.

Conclusions: Overall QoL was maintained in pts treated with alpelisib+fulvestrant.
NCT02437318

03 - PATIENT-REPORTED OUTCOMES (PROS) IN PATIENTS (PTS) WITH PIK3CA-MUTATED HORMONE RECEPTOR-POSITIVE (HR+), HUMAN EPIDERMAL GROWTH FACTOR RECEPTOR-2–NEGATIVE (HER2–) ADVANCED BREAST CANCER (ABC) FROM SOLAR-1