Abstract 4139609: Impact of Metformin on Cardiovascular Outcomes in Breast Cancer Patients Receiving Chest Radiation Therapy

Introduction: Metformin has anti-inflammatory and anti-oxidant properties that have been associated with protective effects against radiation in animal studies. However, there is limited evidence demonstrating similar effects in humans. This study evaluated the impact of metformin on cardiovascular outcomes in breast cancer patients receiving chest radiotherapy. Methods: A retrospective propensity-matched analysis of women aged 18-65 with breast cancer who received chest radiotherapy between January 1, 2000, and December 31, 2018, using the TriNetX database. The patients were categorized into two groups - metformin users (used metformin within 3 months before or after exposure to chest radiation therapy) and metformin non-users. Adjusted odds ratio (aOR) for outcomes was calculated and the Kaplan-Meier survival curve using log-rank tests for a five-year follow-up was performed. All analyses were performed using R software. Result: 131 patients were propensity-matched to each group (Table 1). None of the patients was dialysis-dependent or had chronic liver disease and none was taking SGLT2i. The median number of days of follow-up was 1825 days. Major adverse cardiovascular events – MACE, a composite of all-cause mortality, Heart failure, Myocardial infarction, and cerebrovascular accident - were comparable between metformin users and non-users (19.8% vs 19.3%, aOR: 1.03, 95%CI: 0.54-1.97, p=0.923). Survival probability at 5 years was also comparable in both groups (78.5% vs 79.1%, Hazard ratio = 1.04, 95% CI (0.59 – 1.86), p=0.89) (fig. 1). Conclusion: Metformin use around the time of radiation therapy did not significantly lower or increase the future risk of MACE in breast cancer patients.