Background: Given the conflicting results from observational studies, we assessed whether the use of metformin after a prostate cancer diagnosis is associated with a decreased risk of cancer-specific and all-cause mortality.
Methods: This study was conducted linking four databases from the United Kingdom. A cohort of men newly-diagnosed with non-metastatic prostate cancer with a history of treated type 2 diabetes, between April 1, 1998 and December 31, 2009, was followed until October 1, 2012. Nested case-control analyses were performed for cancer-specific mortality and all-cause mortality, where exposure was defined as use of metformin during the time to risk-set. Conditional logistic regression was used to estimate adjusted rate ratios (RRs) of each outcome with 95% confidence intervals (CIs).
Results: The cohort consisted of 935 men with prostate cancer and a history of type 2 diabetes. After a mean follow-up of 3.7 years, 258 deaths occurred, including 112 from prostate cancer. Overall, the post-diagnostic use of metformin was not associated with a decreased risk of cancer-specific mortality (RR: 1.09, 95% CI: 0.51-2.33). In a secondary analysis, a cumulative duration ≥ 938 days was associated with an increased risk (RR: 3.20, 95% CI: 1.00-10.24). The post-diagnostic use of metformin was not associated with all-cause mortality (RR: 0.79, 95% CI: 0.50-1.23).
Conclusion: The use of metformin after a prostate cancer diagnosis was not associated with an overall decreased risk of cancer-specific and all-cause mortality.
Impact: The results of this study do not support a role for metformin in the prevention of prostate cancer outcomes.
Bensimon L, Yin H, Suissa S, Pollak MN, Azoulay L. Are you the author?
Centre for Clinical Epidemiology, Jewish General Hospital; Centre for Clinical Epidemiology, McGill University, Jewish General Hospital; Departments of Experimental Medicine and Oncology, McGill University.
Reference: Cancer Epidemiol Biomarkers Prev. 2014 Jul 13. pii: cebp.0056.2014.