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.
Written by:
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.
doi: 10.1158/1055-9965.EPI-14-0056
PubMed Abstract
PMID: 25017246
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