New-Onset Diabetes after an Obesity-Related Cancer Diagnosis and Survival Outcomes in the Women's Health Initiative.

BACKGROUND: Individuals diagnosed with an obesity-related cancer (ORC survivors) are at an elevated risk of incident diabetes compared with cancer-free individuals, but whether this confers survival disadvantage is unknown. METHODS: We assessed the rate of incident diabetes in ORC survivors and evaluated the association of incident diabetes with all-cause and cancer-specific mortality among females with ORC in the Women's Health Initiative cohort (N = 14,651). Cox proportional hazards regression models stratified by exposure-risk periods (0-1, >1-3, >3-5, >5-7, and >7-10 years) from ORC diagnosis and time-varying exposure (diabetes) analyses were performed. RESULTS: Among the ORC survivors, a total of 1.3% developed diabetes within ≤1 year of follow-up and 2.5%, 2.3%, 2.3%, and 3.6% at 1-3, 3-5, 5-7, and 7-10 years of follow-up, respectively, after an ORC diagnosis. The median survival for those diagnosed with diabetes within 1-year of cancer diagnosis and those with no diabetes diagnosis in that time frame was 8.8 [95% confidence interval (CI), 7.0-14.5) years and 16.6 (95% CI, 16.1-17.0) years, respectively. New-onset compared with no diabetes as a time-varying exposure was associated with higher risk of all-cause (HR, 1.27; 95% CI, 1.16-1.40) and cancer-specific (HR, 1.17; 95% CI, 0.99-1.38) mortality. When stratified by exposure-risk periods, incident diabetes in ≤1 year of follow-up was associated with higher all-cause (HR, 1.76; 95% CI, 1.40-2.20) and cancer-specific (HR0-1, 1.82; 95% CI, 1.28-2.57) mortality, compared with no diabetes diagnosis. CONCLUSIONS: Incident diabetes was associated with worse cancer-specific and all-cause survival, particularly in the year after cancer diagnosis. IMPACT: These findings draw attention to the importance of diabetes prevention efforts among cancer survivors to improve survival outcomes.