Cross-sectional study of treatment approaches of luminal HER2negative metastatic breast cancer in real practice in Moscow

Introduction: The systemic therapy of patients with metastatic luminal HER2 negative breast cancer (mBC) in cludes various options, which can be fundamentally divided into endocrine therapy and chemotherapy. According to the Clinical Guidelines, both international and Russian, the “gold standard” of the 1st line therapy for patients with metastatic luminal HER2 negative breast cancer (mBC) is a combination of cyclindependent kinase inhib itors 4 / 6 (iCDK4 / 6) with endocrine therapy (ET). However, until recently we did not have complete data on the characteristics of the Russian population of patients with luminal HER2 breast cancer, their treatment options, and the results of this therapy. Aim: To analyze the patients’ profile and current treatment approaches for patients with luminal HER2 mBC in routine clinical practice in Moscow. Materials and methods: The study was performed as an observational, crosssectional and retrospective study. The data of 2,500 patients from medical institutions in Moscow who received systemic therapy for luminal HER2 mBC in AugustOctober 2021 were analyzed. Results: The largest number of patients received iCDK4 / 6 + ET in the first and second lines: 69.0 % and 52.0 %, respectively. In the first line, 54.6 % of patients received ribociclib, 43.1 % palbociclib and 2.3 % abemaciclib. In the second line, 50.6 % of patients received ribociclib, 47.8 % palbociclib and 1.6 % abemaciclib. As the pretreatment of patients increased, preference was given to other treatment methods, therefore the proportion of combined ET decreased to 34.0 % in the third line and 25.0 % in the fourth and subsequent lines. Conclusion: The data obtained indicate that the appointment of iCDK4 / 6 + ET is made in accordance with the Clinical Guidelines for the treatment of breast cancer of the Ministry of Health of the Russian Federation from 2021 and the preferred firstline treatment option for patients with luminal HER2 mBC in Moscow is combined endocrine therapy.