Differences in cancer survival among white and black cancer patients by presence of diabetes mellitus: Estimations based on SEER-Medicare-linked data resource.

Diabetes prevalence and racial health disparities in the diabetic population are increasing in the US. Population-based cancer-specific survival estimates for cancer patients with diabetes have not been assessed. The Surveillance, Epidemiology, and End Results (SEER)-Medicare linkage provided data on cancer-specific deaths and diabetes prevalence among 14 separate cohorts representing 1 068 098 cancer patients ages 66 +  years diagnosed between 2000 and 2011 in 17 SEER areas. Cancer-specific survival estimates were calculated by diabetes status adjusted by age, stage, comorbidities, and cancer treatment, and stratified by cancer site and sex with whites without diabetes as the reference group. Black patients had the highest diabetes prevalence particularly among women. Risks of cancer deaths were increased across most cancer sites for patients with diabetes regardless of race. Among men the largest effect of having diabetes on cancer-specific deaths were observed for black men diagnosed with Non-Hodgkin lymphoma (NHL) (HR = 1.53, 95%CI = 1.33-1.76) and prostate cancer (HR = 1.37, 95%CI = 1.32-1.42). Diabetes prevalence was higher for black females compared to white females across all 14 cancer sites and higher for most sites when compared to white and black males. Among women the largest effect of having diabetes on cancer-specific deaths were observed for black women diagnosed with corpus/uterus cancer (HR = 1.66, 95%CI = 1.54-1.79), Hodgkin lymphoma (HR = 1.62, 95%CI = 1.02-2.56) and breast ER+ (HR = 1.39, 95%CI = 1.32-1.47). The co-occurrence of diabetes and cancer significantly increases the risk of cancer death. Our study suggests that these risks may vary by cancer site, and indicates the need for future research to address racial and sex disparities and enhance understanding how prevalent diabetes may affect cancer deaths.