Diabetes and Cancer-Specific Survival: A Nationwide Population-Based Cohort Study Across Multiple Cancer Sites

Background: Cancer patients with concurrent diabetes generally show poorer survival compared with nondiabetic patients. Aims: We examined the relationship between Type 2 diabetes and cancer-specific survival in the 13 most common cancer sites within a large population-based cohort in Finland. We hypothesized that survival would be lower among patients with diabetes across cancer types. Methods and Results: The cohort, derived from the Finnish CARING Project, included 49 799 incident cancer cases: 25 899 in patients with diabetes and 23 900 in nondiabetic patients. The mean age at diagnosis was 72.2 years, and 40.9% were women. During a mean follow-up of 3.8 years (188 329 person-years), 13 602 cancer deaths occurred. The impact of diabetes on prognosis varied by cancer type. Survival was substantially lower for stomach, endometrial, and lympho-hematological cancers, and slightly lower for colon and breast cancer. Conversely, patients with diabetes had higher survival for liver and rectal cancer. No notable differences were observed for pancreatic, bladder, kidney, prostate, lung, or nonmelanoma skin cancer. Conclusion: Future studies should focus on the biological and metabolic factors influencing cancer survival in patients with diabetes and on how treatment strategies can be optimized to reduce excess cancer mortality in this patient group.