Treatment sequence for hormone receptor-positive HER2-negative advanced breast cancer: Results of a retrospective analysis of Russian patients diagnosed with aBC in 2014-2021.

person Marina Stenina Federal State Budgetary Institution, N.N. Blokhin National Medical Research Center of Oncology of the Ministry of Health of the Russian Federation, Moscow, Russia info_outline Marina Stenina, Lyudmila Zhukova, Daniil Stroyakovskiy, Vera V. Karaseva, Sergei Tjulandin

Authors person Marina Stenina Federal State Budgetary Institution, N.N. Blokhin National Medical Research Center of Oncology of the Ministry of Health of the Russian Federation, Moscow, Russia info_outline Marina Stenina, Lyudmila Zhukova, Daniil Stroyakovskiy, Vera V. Karaseva, Sergei Tjulandin Organizations Federal State Budgetary Institution, N.N. Blokhin National Medical Research Center of Oncology of the Ministry of Health of the Russian Federation, Moscow, Russia, N.N. Blokhin Cancer Research Center, Moscow, Russian Federation, Moscow City Oncology Hospital, Moscow, Russian Federation, Russian Society of Clinical Oncology, Moscow, Russian Federation, Federal State Budgetary Institution N.N. Blokhin National Medical Research Center of Oncology of the Ministry of Health of the Russian Federation (N.N. Blokhin NMRCO), Moscow, Russian Federation Abstract Disclosures Research Funding Pharmaceutical/Biotech Company Russian Society of Clinical Oncology Background: CDK4/6 inhibitors (CDK4/6i) in combination with endocrine therapy (ET) have dramatically changed therapeutic landscape of hormone receptor-positive HER2-negative advanced breast cancer (HR+ HER2- aBC). There are three iCDK4/6 in Russia, which are available and included into the clinical guidelines as a preferred first line treatment option beginning since 2018. The aim of this study was to assess evolution of treatment approaches to HR+ HER2- aBC and identify demographic and disease characteristics in correlation with available groups of therapy (chemotherapy, endocrine therapy ±mTOR inhibitors/ CDK4/6i). Methods: Аdult patients diagnosed with de novo or recurrent HR+ HER2- aBC in 2014-2021 identified in outpatient departments of Moscow state oncology hospitals were included into our non-interventional, descriptive, retrospective cohort study. Primary objective of this real-world study was to describe the rate of CDK4/6i usage in the first line setting. As a secondary objective, we describe patient and disease characteristics in iCDK4/6 group, as well as in the endocrine monotherapy and chemotherapy groups. Results: From the cohort of 1000 patients (full-set analysis population) 874 cases were selected, who received treatment since 2018. 45.9% (95% CI 42.6, 49.2) patients were treated with CDK4/6i in combination with endocrine therapy in the first-line setting. From them in the subgroups of patients with or without visceral metastases 50.5% (95% CI 45.5, 55.5) and 42.1% (95% CI 37.7, 46.5) were treated with CDK4/6i in the first line setting, respectively. Among 874 cases 78.0% (95% CI 75.3, 80.7) patients received endocrine therapy ± targeted therapy; in the subgroups of patients with or without visceral metastases 69.5% (95% CI 64.9, 74.1) and 84.9% (95% CI 81.7, 88.1) were treated with endocrine therapy ± targeted therapy in the first line setting, respectively. Conclusions: Endocrine therapy is a predominant therapeutic option in the first line setting for HR+ HER2- aBC. Clinical trial information: NCT04852081. Treatment choice in the 1st – 3rd lines in 2018-2021 period. 1 st line, 2018-2021 (n=874), % 2nd line 2018-2021 (n=706), % 3rd line 2018-2021 (n=324), % monoET 31.6 18.0 9.0 ET+CDK4/6i 45.9 30.4 25.3 Other comb. ET 0.5 21.7 12.3 Chemotherapy 22.0 29.9 53.4