Purpose: To determine the influence of diabetes mellitus on long-term outcomes and treatment-related toxicity among patients with curatively resected colon cancer.
Patients and methods: This study was a cohort study within a large, randomized adjuvant chemotherapy trial of 3,759 patients with high-risk stage II and stage III colon cancer treated between 1988 and 1992 throughout the United States. In the cohort, 287 patients were identified as having diabetes mellitus. With a median follow-up of 9.4 years, we analyzed differences in overall survival (OS) and colon cancer recurrence as well as treatment-related toxicity between patients with diabetes and those without diabetes.
Results: At 5 years, patients with diabetes mellitus, compared with patients without diabetes, experienced a significantly worse disease-free survival (DFS; 48% diabetics v 59% nondiabetics; P <.0001), OS (57% v 66%; P <.0001), and recurrence-free survival (RFS; 56% v 64%, P =.012). Median survival was 6.0 years and 11.3 years for diabetics and nondiabetics, respectively. Compared with patients without a history of diabetes, those with diabetes had a 42% increased risk of death from any cause (P <.0001) and 21% increased risk for recurrence (P =.05) after adjustment for other predictors of colon cancer outcome. Treatment-related toxicities were similar between the two groups, although patients with diabetes experienced an increase in treatment-related diarrhea.
Conclusion: Patients with diabetes mellitus and high-risk stage II and stage III colon cancer experienced a significantly higher rate of overall mortality and cancer recurrence, even after adjustment for other predictors of colon cancer outcome. These results underscore the need for further research to understand the mechanism that underlies this relation.