Diabetes mellitus and risk of cancer-specific mortality among patients with clear cell renal cell carcinoma undergoing nephrectomy.
516 Background: The impact of diabetes mellitus (DM) on outcomes in patients with renal cell carcinoma (RCC) is controversial. Herein, we evaluated the association of DM with survival among patients with RCC. Methods: We reviewed 2,589 patients treated with nephrectomy for sporadic, unilateral, M0 RCC between 1990 and 2008 and compared demographic and tumor characteristics in patients with and without DM (nonDM). Patients with DM (n=313) were matched 1:2 to nonDM patients according to date of surgery, age, smoking status, obesity, ECOG performance status (PS), CKD stage, histological subtype, and nuclear grade. Cancer-specific (CSS) and overall survival (OS) were compared by Kaplan-Meier analysis. The association of DM with outcomes was evaluated with Cox proportional hazards regression models. Results: A total of 313 (12%) patients had DM. DM patients were significantly older at RCC diagnosis, more likely to be obese, and had higher Charlson scores, CKD class, rates of smoking, and worse PS at surgery (p<0.001). Patients with DM were also more likely to have ccRCC (83% vs. 76%, p=0.02) and to undergo nephron-sparing surgery (42% vs. 35%, p=0.01), while other pathologic features were similar in DM and nonDM. Among the 939 matched cases and controls, 463 patients died within a median of 5.5 years after nephrectomy. Median follow-up for survivors was 8.6 years. Five-year CSS was not significantly different among DM patients 84% vs. nonDM patients 87% (p=0.11), although 5-year OS was significantly worse among DM patients (66% vs. 75%; p<0.001). Indeed, even after adjusting for Charlson score, DM patients were noted to have a significantly increased risk of all-cause mortality (HR 1.33; p=0.004). In a subanalysis of patients with clear cell RCC, DM patients were more likely to die from RCC compared with nonDM patients after adjusting for the SSIGN (Stage, Size, Grade, Necrosis) score (HR 1.44; p=0.034). Conclusions: In this surgical cohort, DM was independently associated with decreased CSS among patients with ccRCC and with decreased OS in all RCC subtypes. Further studies to determine the potential biologic mechanism for this interaction are warranted.