Abstract PS1-08-11: Palbociclib in real clinical practic: Results of a single-center observational study

Abstract Goals: Analyze of palbociclib using for treating patients with HR+/HER2- advanced breast cancer (mBC) at the Republican Clinical Oncology Dispensary. Methods: Data from 323 patients were analyzed. Our study examined the effectiveness of combination endocrine therapy with palbociclib in patients with metastatic HR+ HER2- breast cancer. Data on the clinicopathological characteristics of patients and disease progression during palbociclib administration were obtained by reviewing clinical data from patient records and radiological/pathological examination reports. Results: The median age of patients included in the study was 62 years. When assessing the antitumor response, a partial response was recorded in 54 patients (16.7%), stabilization in 212 patients (65.6%), and progression in 57 patients (17.8%). The median progression-free survival was 13 months. Grade 3 adverse events were noted in 23 patients: neutropenia in 21.7% of cases, hepatotoxicity in 47.8% of cases, cardiotoxicity in 17.4% of cases, and coagulopathy in 4.3%. No patient discontinued therapy due to adverse events. The best treatment results were achieved by patients who used the combination of palbociclib with an endocrine partner as the first line of treatment for advanced stage. The assessment of overall survival in our study showed slightly worse results than in the registration studies. The predicted median was 31 months, whereas in PALOMA-2 and -3 these indicators were 34-37 months; the 20-month survival rate in the PALOMA-3 study was also at the level of 60%, but in PALOMA-2 this indicator reached 80%. The effect of the depth of response to therapy and the time to subsequent progression was statistically significant; patients with stabilization of the tumor process on therapy with palbociclib had a higher risk of progression than those with a partial response. No cases of complete response were reported, and the frequency of disease control was 82.4%, which turned out to be quite close to the results of the PALOMA-2 study - 84.9% and higher than the results of therapy in PALOMA-3 - 66.6%. Conclusions: This analysis of real-world data on the use of palbociclib in real-world clinical practice confirms the RCT data on the efficacy and safety of using CDK4/6 inhibitors for the treatment of patients with HR+ HER2- mBC. Citation Format: A. Sultanbaev, I. Kolyadina, K. Menshikov, S. Musin, S. Nadezda. Palbociclib in real clinical practic: Results of a single-center observational study [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS1-08-11.