The role of diabetes mellitus in localized and metastatic renal cell carcinoma

Introduction & Objectives: Until recently, the incidence of renal cell carcinoma (RCC) has been increasing worldwide, mainly in western countries, at a rate between 2% and 4% per year. However, the reason for this dramatic increase in number has not been fully understood. Diabetes mellitus (DM) is a known risk factor for RCC, but the impact of DM on the prognosis of RCC is unclear. In the present study, we investigated the potential influence of DM on clinicopathological features of localized and metastatic RCC. Material & Methods: We evaluated 863 patients with primary RCC who had undergone renal surgery between 1991 and 2005 in the University Hospital Hannover; the mean follow-up was 58 months. To test the association of DM with survival end-points, Kaplan-Meier Method and Cox multivariable logistic regression models were applied. Results: In total, we identified 123 diabetic patients who suffered from RCC, 9 patients with diabetes type 1 and 114 with type 2. Patients with DM type 2 presented significantly more often with pT1a tumours at diagnosis (40.0 vs. 31.7%, p = 0.02), had less frequently high grade cancer (G3/4; 10.3 vs. 16.2%, p = 0.03), were older (median, 65.3 vs. 61.6 years; p < 0.001), and had a higher BMI at diagnosis (median, 27.6 vs. 25.8, p < 0.001). However, there was no difference between diabetic and non-diabetic patients concerning sex, histological subtype, lymphatic and distant metastasis. In addition, there was no discrepancy in 5-year cancer specific survival between both groups (62.2 vs. 64.9% for patients without and with DM type 2, respectively). Applying multivariable analysis, unlike age, tumour stage, grade and N/M status, diabetes was not identified as a significant independent prognostic factor. Conclusions: To our knowledge this is the first study to show that even though diabetes is a risk factor for RCC it does not seem to influence its prognoses even though it might be diagnosed earlier in diabetic patients.