Analysis of pharmacotherapy in patients with HR+HER2- metastatic breast cancer with PIK3CA mutations in real clinical practice

Background. The most common type of breast cancer (BC) is hormone receptor-positive HER2-negative (HR+ HER2-) tumors, approximately 40% of which have mutations in the PIK3CA oncogene encoding the catalytic subunit of the PI3K protein. The most effective pharmacotherapy for such neoplasms is the use of a combination of PI3Kα-specific inhibitors alpelisib and fulvestrant. However, in real clinical practice, the use of this combination did not become available immediately.

Objective. Retrospective analysis of the efficacy of various drug therapy options in the study cohort of patients in real clinical practice.

Methods. The study included 34 patients with HR+/HER2- metastatic breast cancer with PIK3CA mutation, who received treatment at the Primorsky Regional Oncology Dispensary.

Results. The median EFS in the group receiving CDk4/6 inhibitors was 27.00 months (95% CI: 18.00–78.00), and in the group not receiving CDk4/6 inhibitors it was 8.00 months (95% CI: 3.00–39.00), P=0.020. The median EFS in the alpelisib group was 65.00 months (95% CI: 19.00–78.00), the median EFS in the other therapy group (not receiving alpelisib) was 9.00 months (95% CI: 7.00–27.00). The differences in EFS were statistically significant (P=0.025).

Conclusion. Effective pharmacotherapy options for the study group of patients include the use of both CDk4/6 inhibitors and the PIK3 inhibitor alpelisib in combination with fulvestrant. Despite a number of limitations, the RWD study demonstrated improved survival outcomes for patients who were prescribed any CDk4/6 inhibitor and alpelisib.