Target therapy of luminal HER2-negative advanced breast cancer with PIK3CA mutation: combination of alpelisib plus fulvestrant in real clinical practice

Abstract

Introduction. Сombination of alpelisib plus fulvestrant is approved in patients with hormone receptor positive, HER2-negative, PIK3CA-mutated advanced breast cancer (ABC) after progression on hormonotherapy. Efficacy data of alpelisib in heavily pretreated patients with HR+/HER-2-, PIK3CA-mutated advanced breast cancer are limited, only results from phase I trial are available. Here we report our results of alpelisib efficacy in 19 heavily pretreated patients.Object: to evaluate efficacy and safety of combination alpelisib plus fulvestrant in patients with HR+/HER2-, PIK3CA-mutated advanced breast cancer in initial and later lines of therapy in real clinical practice.Materials and methods. Combination of alpelisib plus fulvestrant was investigated in 19 patients with HR+/HER2-, PIK3CAmutated ABC, alpelisib at a dose of 300 mg per day plus fulvestrant at a dose of 500 mg i.m. every 28 days and once on day 15. Treatment continued until disease progression or unacceptable toxicity.Results. From February 2021 19 patients with HR+/HER2-, PIK3CA-mutated advanced breast cancer were treated with alpelisib plus fulvestrant. The data cut off is October 2021. Median lines of treatment in advanced disease was five, including 19 (100%) patients received CDK4/6, 14 (74%) – fulvestrant and/or everolimus and 15 (79%) – chemotherapy. 4 (21%) received alpelisib in a second line, 15 (79%) – in subsequent lines. Median progression-free survival was 7 months. The response was evaluated in 18 patients: partial response was achieved in 5 (28%) patients, stable disease – in 9 (50%), disease progression – 4 (22%). The most frequent adverse events were hyperglycemia – 74% (grade 3 – 22%), creatinine increased – 42% and rash – 37% (grade 3 – 22%). Only one patient has discontinued the treatment due to Quincke`s edema.Conclusions. Combination of alpelisib with fulvestrant is an effective option both in initial and later lines of therapy in patients with HR+/HER2-, PIK3CA-mutated advanced breast cancer including fulvestrant, CDK4/6 inhibitors and/or everolimus – pretreated patients.