Aims/hypothesis: Diabetes is associated with increased risk of cancer at several sites, but its association with cancer of the kidney is unclear. We performed a systematic review with meta-analysis to examine the association between diabetes and incidence of kidney cancer.
Methods: Pertinent studies were identified by searching PubMed (from January 1966 to December 2010) and reviewing the reference lists of relevant articles. We included cohort studies reporting RR estimates and 95% CI (or data to calculate them) of the association between diabetes and kidney cancer incidence. Summary RRs were calculated using a random-effects model.
Results: Nine cohort studies met the inclusion criteria. Analysis of all studies showed that compared with individuals without diabetes, patients with diabetes had a statistically significant increased risk of kidney cancer (RR 1.42, 95% CI 1.06-1.91). There was heterogeneity among studies (p < 0.001 for heterogeneity). The association was stronger in women (RR 1.70, 95% CI 1.47-1.97) than in men (RR 1.26, 95% CI 1.06-1.49). When restricting the analysis to studies that had adjusted for body mass index (n = 3) or cigarette smoking (n = 3), the RRs were 1.12 (95% CI 0.99-1.27) and 1.29 (95% CI 1.05-1.58), respectively.
Conclusions/interpretation: This meta-analysis indicates a positive association between diabetes and risk of kidney cancer. Future research should attempt to establish whether this association is causal.