Meta-analysis Of The Relationship Between Diabetes And Kidney Cancer Risk

Background and Objective:Kidney cancer is one of the most common urological malignancy in adults, and it accounts for 3%-4% of all cancers. According to statistics, the incidence of this disease has increased at a rate of 2.5% since 1970. Although pathogenesis of kidney cancer is still unclear, many factors have been deemed to influence the occurrence and development of it, such as smoking, obesity and hypertension. It is well known that these factors are associated with diabetes. Hence, there is a potential association between diabetes and kidney cancer, because they share the same risk factors. Evidences from epidemiologic studies have identified the relationship between diabetes and kidney cancer risk, but the results were inconsistent. In order to make the relationship between diabetes and kidney cancer risk clear, we conducted a meta-analysis based on both case-control studies and cohort studies.Materials and Methods:Databases of PubMed, VIP, CNKI were used to searched for studies which regarded the relationship between diabetes and kidney cancer risk up to March 2015. The reference lists of the included articles were checked, and we contacted the authors of the primary studies for additional information when necessary. The process of study selection, data extraction and quality assessment were conducted by two independent individuals. The analysis was performed by using STATA 12.0 software. Based on the random-effects model, RRs and the corresponding 95% CIs were used to measure the association between diabetes and the risk of kidney cancer. Subgroup-analyses were conducted to assess the effects of various study characteristics on the pooled RR. In addition, we conducted a sensitivity analysis to assess the influence of each individual study on pooled RR. At last, publication bias was detected by Begg’s and Egger’s test. In our study, if the P value was less than 0.05, it was considered to be statistical significance.Results:After retrieving all the databases, 26 studies involving 17 cohort studies and 9 case-control studies were included. The cohort studies had 3014450 participants with 6063 being the cases; The case-control studies consisted of 4344 patients in the case group and 465862 participants in the control group. According to the NOS, all studies were of high quality since the score was greater than 5.Meta-analysis was performed in a random-effects model to estimate the association of diabetes with the risk of kidney cancer. We found a significant positive relationship between diabetes and kidney cancer risk(RR 1.44, 95% CI 1.29-1.60). But we observed a strong evidence of heterogeneity(I2=95.4%, P<0.05). We also found type 2 diabetes may increase the risk of kidney cancer(RR 1.55, 95% CI 1.31-1.84).Based on different design types, we divided the included studies into 2 subgroups. The relationship between diabetes and the risk of kidney cancer was not significantly changed both in cohort studies(RR 1.47, 95% CI 1.30-1.67) and case-control studies(RR 1.33, 95% CI 1.15-1.54). According to the gender difference, we divided the included studies into 2 subgroups. The significant positive association between diabetes and kidney cancer risk was stronger in the females(RR 1.51, 95% CI 1.32-1.72) compared with that in the males(RR 1.34, 95% CI 1.18- 1.51). In subgroup analyses, a elevated rate of kidney cancer among individuals with diabetes was observed in studies conducted in Americans(RR 1.33, 95% CI 1.15-1.54) and Asians(RR 1.38, 95% CI 1.25-1.51), and the association was more significant in Europeans(RR 1.41, 95% CI 1.16-1.71). Sensitivity analysis showed the positive association between diabetes and kidney cancer risk was not modified after excluding each study, which suggested the results were stable. Funnel plot did not show any substantial asymmetry. Begg’s and Egger’s regression test indicated little evidence of publication bias(P>0.05).Conclusion:Our meta-analysis shows that diabetes probably can increase the risk of kidney cancer,especially for type 2 diabetes. More multi-center studies which adjust for diabetes subtype, kidney cancer subtype, receiving hypoglycemic drugs and other potential confounders should be done to provide reliable basis for the association between diabetes and kidney cancer. Because the concrete mechanism about how diabetes influence the risk of kidney cancer is unclear, and little attention is paid to the association between diabetes and kidney cancer mortality, further research is needed.