Background: The relationship between type 1 diabetes mellitus (T1DM) and cancer incidence remains unclear. We sought to assess the all-cause and site-specific cancer incidence in patients with T1DM. Methods: A retrospective cohort study design was employed, in which 14 619 patients with T1DM were retrieved from Taiwan's National Health Insurance medical claims between 2000 and 2007. The study subjects were followed to the end of 2008, and cancer incidence was assessed. We calculated age-, sex-, and calendar year-standardized incidence ratios (SIRs) of all-cause cancer incidence and site-specific neoplasm incidence, with reference to the general population. Results: Seven hundred and sixty patients were identified for all-cause cancer over 86 610 person-years, representing an incidence rate of 87.75 cases per 10 000 person-years. The incidence rate was higher in males than in female patients (109.86 vs 69.75 cases per 10 000 person-years). T1DM was associated with a significantly increased SIR of all-cause cancer (1.13; 95% confidence interval [CI], 1.05-1.22). The sex-specific SIR was significantly elevated in female patients (1.19; 95% CI, 1.07-1.33), but the SIR for male patients was insignificantly elevated (1.09; 95% CI, 0.99-1.20). Pancreatic cancer showed the greatest increase in SIR among both male and female patients with T1DM. Male patients experienced significantly increased SIRs for kidney, rectum, liver, and colon neoplasm, and significantly increased SIRs were noted for ovarian, bladder, and colon cancer in female patients. Conclusions: T1DM was associated with a 13% increase in risk of all-cause cancer incidence. Patients with T1DM should be advised to undergo cancer screening for certain types of cancer.
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