(HealthDay News) — Among elderly men with diabetes, increased cumulative duration of metformin following a prostate cancer (PC) diagnosis correlates with decreased all-cause and PC-specific mortality, according to a study published online Aug. 5 in the Journal of Clinical Oncology.

David Margel, M.D., Ph.D., from the University of Toronto, and colleagues analyzed data from several Ontario health care administrative databases to identify men (>66 years) with incident diabetes who subsequently developed PC. Within the cohort of 3,837 patients, they examined the impact of duration of antidiabetic medication exposure following diagnosis with PC on all-cause and PC-specific mortality.

The researchers found that the median age at PC diagnosis was 75 years. Over a median of 4.64 years of follow-up, 35% of patients died, with 7.6% dying from PC. The risk of PC-specific and all-cause mortality was significant decreased, in a dose-dependent manner, for cumulative duration of metformin treatment after PC diagnosis.

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For PC-specific mortality, the adjusted hazard ratio was 0.76 for each additional 6 months of metformin use. There was also a significant association with all-cause mortality but it declined over time, from a hazard ratio of 0.76 in the first 6 months to 0.93 between 24 and 30 months. For other antidiabetic drugs there was no relationship with cumulative use and either outcome.

“Increased cumulative duration of metformin exposure after PC diagnosis was associated with decreases in both all-cause and PC-specific mortality among diabetic men,” the authors write.