The impact of type 2 diabetes mellitus on cancer-specific survival A Follow-Up Study in Sweden

BACKGROUND: Earlier studies have suggested that type 2 diabetes mellitus (T2DM) alters the risk of developing a variety of cancers, but little has been known about the impact of T2DM on cancer prognosis. On the basis of nationwide population-based Swedish registries, the authors of this report compared the cause-specific survival among cancer patients with and without T2DM. METHODS: Patients with T2DM were identified from the nationwide Swedish Hospital Discharge Register, and cancers were recorded from the Swedish Cancer Registry. Hazard ratios (HRs) were calculated using Cox regression models to compare variations in cause-specific survival between cancer patients with and without T2DM. RESULTS: Of the 1016,105 cancer patients, 16,123 had been hospitalized with T2DM before their diagnosis of cancer. The mortality rate was significantly higher among cancer patients with T2DM than among those without T2DM (cause-specific HR, 1.38; 95% confidence interval, 1.35-1.41). There were no differences in TNM stage distribution among cancer patients with or without T2DM for the main cancers, with an exception of tumor and metastatic classifications for breast cancer and prostate cancer, respectively. CONCLUSIONS: The current results indicated that patients with T2DM who are diagnosed with a subsequent cancer are at an increased risk for cause-specific mortality compared with patients who have cancer without T2DM. Cancer 2012; 118: 1353-61. (C) 2011 American Cancer Society.