Abstract P2-06-04: Effects of BMI velocity on outcomes in patients with metastatic breast cancer in the Dallas Metastatic Breast Cancer Study

Abstract

Abstract BACKGROUND: The Dallas Metastatic Breast Cancer Study (DMBCS) is a clinical database that was established in 2021 at a single academic medical system to track patient demographics, associated pathology, treatments, and other variables that are not widely available in the Surveillance, Epidemiology, and End Results (SEER) Program for metastatic breast cancer (MBC). One of many ongoing studies as part of the DMBCS is to investigate how weight loss after diagnosis affects outcomes in MBC patients. Although previous studies have shown that significant weight loss is associated with poorer outcomes in certain cancer types, little is known about its role in breast cancer. METHODS: 139 patients who were diagnosed with MBC between 2009-2021 were included in this data collection. BMI at the time of diagnosis of MBC and within 6 months of death or last follow-up were recorded. BMI velocity was calculated by dividing the difference between BMI at diagnosis and BMI at time of death (or last follow-up) by the number of months between initial diagnosis and time of death (or last follow-up). The BMI velocity represents the rate at which patients lost or gained weight during their disease course. A negative BMI velocity indicates weight loss, and a positive BMI velocity indicates weight gain over the defined period. The absolute value of the BMI velocity indicates how rapidly someone gains or loses weight. The association of BMI velocity on the primary outcome (overall survival (OS) and progression-free survival (PFS)) was assessed using Cox proportional hazard (PH) model. Adjusted hazard ratios (HR) with 95% confidence intervals were computed using the multivariable Cox PH model. RESULTS: At the time of diagnosis of MBC, 40% were obese and 33% were overweight. At the time of death or last follow-up, 27% were obese and 31% were overweight. The mean BMI velocity was -0.13 per month. Contrary to previous studies that have shown a negative effect of obesity on OS, we found that obesity at the time of diagnosis of MBC did not statistically worsen OS and PFS. However, compared to patients who had negative BMI velocities, improved OS (lower hazard ratio) was noted for patients with stable or increasing BMI velocities (HR = 0.53; 95% CI = 0.32-0.88, p = 0.014). A greater rate of weight loss was also associated with worse OS (HR = 0.23; 95% CI = 0.12 - 0.47, p < 0.001) and PFS (HR = 0.29; 95% CI = 0.16 - 0.52, p < 0.001). Improved PFS was seen for patients with stable or increasing BMI velocities in the unadjusted analysis (HR = 0.65; 95% CI = 0.42 - 0.99, p = 0.047). CONCLUSION: Our study found that contrary to previously published results in patients with early-stage breast cancer, obesity did not statistically worsen OS or PFS. However, the rate of weight loss, which we defined as BMI velocity, is associated with higher mortality in MBC. Our findings can be applied to clinical practice when advising MBC patients regarding healthy changes in weight during their disease course. BMI velocity could be used as a prognostic indicator to predict outcomes in patients with MBC. In future studies, we aim to quantify the amount of weight loss that is associated with worse outcomes. Citation Format: Mir Lim, Mona Pathak, Meng Cao, Anna Moscowitz, Jonathan Ladner, Sangeetha Reddy, Isaac Chan. Effects of BMI velocity on outcomes in patients with metastatic breast cancer in the Dallas Metastatic Breast Cancer Study [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-06-04.