Type 2 diabetes and risk of prostate cancer: a meta-analysis of observational studies

• Published in: Prostate cancer and prostatic diseases Vol. 16; no. 2; pp. 151 - 158
• Main Authors: Bansal, D, Bhansali, A, Kapil, G, Undela, K, Tiwari, P
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01-06-2013; Nature Publishing Group
• Subjects: 692/499; 692/699/2743/137/773; 692/699/2768/466; 692/699/67/2324; Biomedical and Life Sciences; Biomedicine; Cancer; Cancer Research; Case-Control Studies; Confidence intervals; Data analysis; Development and progression; Diabetes; Diabetes mellitus; Diabetes mellitus (non-insulin dependent); Diabetes Mellitus, Type 2 - complications; Epidemiology; Health aspects; Health risks; Humans; Male; Meta-analysis; Observational studies; Observational Studies as Topic; Odds Ratio; Oncology, Experimental; original-article; Outliers (statistics); Prostate cancer; Prostatic Neoplasms - etiology; Risk; Risk Factors; Sensitivity analysis; Subgroups; Type 2 diabetes; Type 2 diabetes; meta-analysis; risk; observational studies
• ISSN: 1365-7852; 1476-5608
• DOI: 10.1038/pcan.2012.40

Background:
Emerging evidence suggests that diabetes may increase the risk of cancers. However, available evidence on prostate cancer is conflicting. We therefore examined the association between Type 2 diabetes and risk of prostate cancer by conducting a detailed meta-analysis of all studies published regarding this subject.
Methods:
PubMed database and bibliographies of retrieved articles were searched for epidemiological studies (published between 1970 and 2011), investigating the relationship between Type 2 diabetes and prostate cancer. Pooled risk ratio (RR) was calculated using random-effects model. Subgroup, sensitivity analysis and cumulative meta-analysis were also done.
Results:
Forty-five studies (29 cohort and 16 case–control studies) involving 8.1 million participants and 132 331 prostate cancer cases detected a significant inverse association between Type 2 diabetes and risk of prostate cancer (RR 0.86, 95% confidence interval (CI) 0.80–0.92). For cohort studies alone, the RR was 0.87 (95% CI 0.80–0.94), and for case–control studies alone, the RR was 0.85 (95% CI 0.74–0.96). Sensitivity analysis done by excluding one outlier further strengthened our negative association (RR 0.83, 95% CI 0.78–0.87). No evidence of publication bias was observed.
Conclusions:
This meta-analysis provides strongest evidence supporting that Type 2 diabetes is significantly inversely associated with risk of developing prostate cancer.