Abstract
Diabetes is a risk factor for colorectal cancer and several reports suggest worse cancer-specific outcomes in diabetes patients. Recent studies in multiple tumour types indicate metformin may positively impact on cancer-specific and overall survival. A population-based series of stage II colorectal cancer patients treated and followed from 2000 to 2013 were analysed for baseline characteristics, treatment, and outcomes. 1116 patients with stage II colon cancer were identified, 55.5% were male and median age was 70.9 years (range 20.5-101.2). The diabetes patients (21.6%, n = 241) were older than nondiabetes patients (median 74.0 versus 69.6, p = 0.0001). There was no impact of diabetes on cancer presentation or pathology. Diabetes patients were less likely to receive adjuvant treatment (13.7 versus 24.8%, p = 0.002) but were equally likely to complete treatment (69.7 versus 67.7%, p = 1.00). Diabetes did not significantly impact cancer recurrence (HR = 1.07, 95% CI 0.71-1.63) or overall survival (HR = 1.23, 95% CI 0.88-1.72), adjusted for age. Diabetes medication did not impact cancer recurrence or survival. Cancer presentation and outcomes in diabetes patients are comparable to those of nondiabetes patients in those with stage II colon cancer. The effect of metformin merits further evaluation in patients with colon cancer.