Effectiveness of Alpelisib plus Fulvestrant Compared with Real-World Standard Treatment Among Patients with HR-Positive, HER2-Negative, PIK3CA Mutation–Positive Breast Cancer

After cyclin-dependent kinase (CDK)4/6 inhibitor with an aromatase inhibitor (AI) as immediate previous therapy, the BYLieve trial confirmed efficacy and safety of alpelisib with fulvestrant for hormone receptor (HR)-positive, HER2-negative, PIK3CA mutation–positive, advanced breast cancer. In a real-world situation, additional analyses were conducted to compare the efficacy of BYLieve with the effectiveness of standard treatment.

Patients whose disease progressed on a CDK4/6 inhibitor plus an AI and were treated with alpelisib with fulvestrant in BYLieve were matched with a real-world patient cohort who received standard-of-care therapy. The primary and secondary objectives were to evaluate progression-free survival (PFS) and the proportion of patients remaining progression-free at 6 months, respectively, between the 2 cohorts.¹

The real-world cohort yielded 855 individuals with PIK3CA mutation–positive illness who had previously received CDK4/6 inhibitors plus hormone therapy; additional matching to 120 patients from BYLieve yielded 95 patients who had never received HER2-targeting medicines, clinical research drugs, or alpelisib. Primary and secondary end points in BYLieve favored alpelisib with fulvestrant treatment over standard therapies in the real-world cohort in unadjusted and postmatching data. Patients treated with alpelisib in BYLieve had a median PFS of 7.3 months versus 3.7 months in the real-world cohort, and a 6-month PFS of 54.6% versus 40.1%, respectively.¹

PIK3CA mutation–positive tumors have been linked to endocrine therapy resistance in approximately 40% of patients with HR-positive, HER2-negative, advanced breast cancer. When coupled with fulvestrant, alpelisib, a selective PI3K inhibitor, dramatically increased PFS in SOLAR-1 and indicated therapeutic effectiveness in BYLieve. The effectiveness of alpelisib coupled with fulvestrant in comparison with normal therapy after CDK4/6 inhibitor treatment is limited.¹

Because the BYLieve trial lacked a comparator arm, matched analyses to a real-world cohort were conducted to provide more context to the findings. Regardless of the strategy utilized, alpelisib paired with fulvestrant showed a consistent benefit in BYLieve cohort A when compared with standard therapies for patients with PIK3CA mutation–positive, HR-positive, HER2-negative, advanced breast cancer, and previous CDK4/6 inhibitor-based therapy, with or without chemotherapy.¹

Reference

1. Turner S, Chia S, Kanakamedala H, et al. Effectiveness of alpelisib + fulvestrant compared with real-world standard treatment among patients with HR+, HER2–, PIK3CA-mutated breast cancer. Oncologist. 2021;26:e1133-e1142.