Real-world data analysis of safety and efficacy of palbociclib in HR positive, HER-2 negative MBC patients, at tertiary care hospital at Middle East, Saudi Arabia.

e13089 Background: In Saudi Arabia, Breast Cancer is the first-ranked cancer among females with a significant increase in incidence over the years, accounting for 28.3% of all new cancer cases in 2022. CDK 4/6 inhibitors with endocrine therapy are standard-of-care 1st line therapy for hormone receptor (HR)-positive and human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer (MBC) patients. This real-world study aims to investigate the clinical outcome and toxicity profile of Palbociclib in HR+, HER2-negative metastatic breast cancer. Methods: Real-world Data Analysis of the clinical outcome and toxicity profile of Palbociclib in HR+, HER2-negative metastatic breast cancer at tertiary care hospital, Saudi Arabia. Data were collected from an electronic health record between January 2021 – September 2024. Patients were excluded if they were male patients and those who did not receive at least one cycle of Palbociclib. Kaplan-Meier survival curves and survival tables were generated to assess the progression-free survival and overall survival of the patients, and to determine cumulative survival rates; the median survival time was estimated accordingly. All data were entered and analyzed using the SPSS Statistics Package (version 25; SPSS Inc., Chicago, Illinois, USA) and MEDCALC software (version 23.0.2). Results: A total of 177 patients with a median age of 58.43 years. One-third had ECOG PS 1, and 77.4% were postmenopausal. Visceral metastases were present in 38.4% of patients. Aromatase inhibitors were the primary endocrine therapy in 65% of cases. Median PFS was 22 months with a cumulative PFS rate of 24%. Median OS was 26.46 months with a cumulative OS rate of 25%. Neutropenia was the most common adverse event, affecting 41.2% of patients, with 34.5% experiencing grade 3 events. Dose reductions were required in 23.7% of patients to manage side effects. Conclusions: This real-world study confirms the efficacy and safety of Palbociclib in HR+/HER2- MBC patients in Saudi Arabia, with PFS and OS compared to clinical trial data. Neutropenia was the most frequent adverse event, requiring dose adjustments. These findings emphasize the need for proactive monitoring and management of neutropenia in this population. Median progression free survival and overall survival clinical data. PFS Median follow-up time Median [IQR] 16 [33 - 9] OS Median follow-up time Median [IQR] 22 [34.50 - 11.00] Median IQR: Interquartile Range.