Abstract
BACKGROUND: Although CDK4/6 inhibitors have demonstrated efficacy globally, real-world data from Vietnam are limited, primarily due to financial constraints. This study aimed to evaluate the effectiveness and toxicity of ribociclib combined with aromatase inhibitors (AIs) in patients with hormone receptor-positive, HER2-negative metastatic breast cancer (mBC) in a real-world study setting. METHODS: This retrospective study included patients with de novo or recurrent hormone receptor-positive, HER2-negative metastatic breast cancer who were treated at two cancer centers between May 2021 and April 2024. The primary endpoint was progression-free survival (PFS), which was analyzed via the Kaplan-Meier method, with comparisons via the log-rank test and Cox regression. The secondary endpoints were the objective response rate (ORR) per RECIST 1.1, overall survival (OS), and adverse events graded by CTCAE 5.0. RESULTS: A total of 92 female patients were eligible for the study. The mean age was 53.8±12.1 years. Among the patients, 69.6% received first line of treatment, and 30.4% were in subsequent lines. The median PFS (mPFS) was 19.1 months (95% CI: 14.3-26.2) in all patients, with a median follow-up time of 28.2 months. The rates of complete response, partial response, stable disease, and progressive disease were 2.2%, 55.4%, 37.0%, and 5.4%, respectively. PFS was lower in patients with liver metastasis (11.7 months vs. 21.8 months, p=0.030). With a median follow-up time of 27.9 months, the median OS was not reached, and the 3-year OS rate was 61.4%. Common adverse events (any grade/grade ≥3) included neutropenia (80.4/47.8%), elevated alanine transaminase (33.7%/3.3%), elevated aspartate transaminase (31.5%/3.3%), nausea (18.5%/0%), and thrombocytopenia (13.0%/0%). No treatment-related deaths were observed. CONCLUSION: Ribociclib combined with aromatase inhibitors demonstrated favorable real-world effectiveness and manageable safety profiles in Vietnamese patients with hormone receptor-positive, HER2-negative metastatic breast cancer in a real-world setting.