Abstract
PURPOSE: Although Body Mass Index (BMI) has been reported to influence breast cancer prognosis, recent evidence challenges the traditional conclusion that high BMI consistently predicts poor prognosis. The aim of this study was to determine the impact of BMI on the efficacy of CDK4/6 inhibitors in patients with metastatic hormone receptor (HR)-positive breast cancer (BC). METHODS: We performed a retrospective chart review of all female patients with metastatic HR-positive BC on a CDK4/6 inhibitor in first- or late-line settings and seen at our academic institution between 2016 and 2023. The primary endpoint was Overall Survival (OS), defined as the time from the start of CDK4/6 inhibitors to death due to any cause. RESULTS: We identified 212 patients who had received a CDK4/6 inhibitor in the first- or second-line settings for metastatic HR-positive BC. Of the 212 patients, 53.3% (113) had a low BMI (defined as < 24 kg/m(2)) and 46.7% (99) had a high BMI (≥ 24 kg/m(2)). In the first-line setting, mean OS was 46.6 months (95% CI, 38.9 to 54.3) in the BMI-low group versus 78.9 months (95% CI, 69.2 to 88.5) in the BMI-high group (p = 0.047). The median PFS was 25 months (95% CI, 19.7 to 30.3) in the BMI-low group versus 33 months (95% CI, 21.4 to 44.6) in the BMI-high group, but the difference between the two groups was not statistically significant (p = 0.488). No statistically significant differences were observed in OS and PFS between the two groups in late-line settings (p = 0.83; p = 0.84). CONCLUSION: In HR positive advanced breast cancer patients treated with first-line CDK4/6 inhibitors, lower BMI is associated with poorer prognosis.