Diabetes Mellitus and Survival Outcomes in Women with Early-Stage Triple-Negative Breast Cancer: A Multicenter Population-Based Cohort Study from Saskatchewan

BACKGROUND: Diabetes mellitus has been associated with worse outcomes in several malignancies, yet its impact on women with early-stage triple-negative breast cancer (TNBC) remains unclear. This multicenter, population-based cohort study evaluated the association between diabetes and survival outcomes in women with TNBC treated with neoadjuvant and/or adjuvant (curative-intent) chemotherapy. METHODS: Adult women diagnosed with stage I-III TNBC in Saskatchewan, Canada (2010-2018), were identified. Patients were categorized by diabetes status. Overall survival (OS), disease-free survival (DFS), and invasive DFS were assessed using Kaplan-Meier methods, with multivariable Cox regression and inverse probability of treatment weighting (IPTW) to control for confounding factors. RESULTS: Among 357 eligible women, 36 (10%) had diabetes. With a median follow-up of 88 months, diabetic women experienced significantly inferior 5-year OS (61% vs. 83%) and DFS (56% vs. 78%) compared with non-diabetic women (p < 0.001). Diabetes was independently associated with worse disease-free survival (hazard ratio [HR] 2.95, 95% CI 1.73-5.04) and overall survival (HR 2.73, 95% CI 1.55-4.79). IPTW analysis confirmed the adverse impact of diabetes on survival. CONCLUSIONS: Diabetes is independently associated with significantly inferior DFS and OS in women receiving curative-intent chemotherapy for early-stage TNBC. Improved diabetes management during cancer care may represent an opportunity to enhance outcomes. Further prospective studies are warranted.