Metformin Use Reduces All-Cause and Prostate Cancer–Specific Mortality in Men With Diabetes
In a study reported in Journal of Clinical Oncology, David Margel, MD, PhD, of University of Toronto, and colleagues examined the effect of duration of antidiabetic medication exposure after prostate cancer diagnosis on all-cause and prostate cancer–specific mortality in men with diabetes. They found that increased duration of metformin use was associated with significantly reduced risk of prostate cancer–specific and all-cause mortality.
Study Details
In this population-based retrospective cohort study, data were obtained from several Ontario health-care administrative databases. A total of 3,837 men aged 66 years or older with incident diabetes who subsequently developed prostate cancer and had pathology reports available were included in the analysis. Median age at diagnosis of prostate cancer was 75 years (interquartile range [IQR] = 72–79 years).
During a median follow-up of 4.64 years (IQR = 2.7–7.1 years), 1,343 patients died (35%) and 291 (7.6%) died as a result of prostate cancer. Overall, 1,251 (32.6%) and 1,619 (42.2%) patients were exposed to metformin before and after prostate cancer diagnosis, respectively, for a median of 19 and 8.9 months, respectively. Among metformin users, 53% continued to take metformin once the medication was initiated and 47% had periods of nonuse.
Reduced Mortality Risk With Metformin
The cumulative duration of metformin treatment after prostate cancer diagnosis was associated with a significantly reduced risk of prostate cancer–specific and all-cause mortality in a dose-dependent fashion. The adjusted hazard ratio (HR) for prostate cancer–specific mortality was 0.76 (95% confidence interval = 0.64–0.89, P = .001) for each additional 6 months of metformin use. The association with all-cause mortality was also significant but declined over time from a hazard ratio of 0.76 in the first 6 months to 0.88 at 6 to 12 months, 0.91 at 12 to 18 months, 0.92 at 18 to 24 months, and 0.93 at 24 to 30 months (all P < .001).
There was no significant relationship between cumulative sulfonylurea, thiazolidinedione, or insulin use and risk of prostate cancer–specific or all-cause mortality.
The authors stated: [C]onsistent with current guidelines, metformin should be considered first-line therapy among patients with prostate cancer and diabetes, not only for diabetes control but possibly to improve cancer prognosis. [In addition] we found that metformin was associated with benefit regardless of cancer treatments. These results suggest that metformin may further improve survival as an adjunct therapy, even among those already receiving optimal cancer treatments. Finally, metformin may be ideal for secondary prevention because it is inexpensive, safe, and well tolerated.”
They researchers cited their findings as support for additional evaluation of metformin in prostate cancer and noted that large-scale phase III studies of metformin in breast cancer are already underway.
The study was supported by the Institute for Clinical Evaluative Sciences.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
