medwireNews: Postdiagnostic metformin or statin use may reduce the risk for death among people with advanced prostate cancer, suggests an analysis of US Veteran Health Administration data.
The impact of metformin, however, may be modified by race, report Saira Khan (St. Louis Veterans Affairs Medical Center, Missouri) and colleagues in Prostate Cancer and Prostatic Diseases.
Their study included 4572 men (mean age 68 years) diagnosed with advanced (T4, M1, or N1) prostate cancer between 1999 and 2013. Of these, 69.8% were White, 29.6% were Black, and 0.6% were of other races.
The participants were followed up for a mean of 4.5 years from diagnosis, during which time 16.6% used metformin and 52.6% used a statin. Similar proportions of Black and White men used metformin (18.3 vs 15.7%), but statin use was less common in Black men than White men (46.9 vs 54.9%).
During follow-up, there were 2762 deaths, with 65.0% attributed to prostate cancer.
After adjustment for potential confounders, the researchers found that postdiagnostic metformin use was associated with significant 16% and 24% reduced risks for all-cause and prostate cancer-specific mortality, respectively, relative to no use.
However, when the cohort was stratified by race, the association was only significant among White men for whom the all-cause and prostate cancer-specific mortality risk reductions were a respective 26% and 35% with metformin use.
Kahn and co-authors comment that, according to previous research, “Black patients are less adherent and more likely to discontinue metformin over time,” which they say could have “biased our time-varying analyses towards the null.”
Postdiagnostic statin use was also associated with improved mortality outcomes. In this case, the risk for all-cause mortality was a significant 25% lower with versus without statins, while the risk for prostate cancer-specific mortality was a significant 28% lower.
Furthermore, the benefit was seen in both Black and White men. In Black men, all-cause mortality was a significant 24% lower among statin users relative to nonusers, while prostate cancer-specific mortality was a significant 29% lower. In White men, the corresponding risk reductions were 25% and 28%.
Kahn et al note that in agreement with their finding of lower statin use among Black men, earlier research indicates that “Black patients are less likely than White patients to receive guideline-concordant statin therapy.”
They therefore “suggest that less than ideal levels of statin-therapy could play a role in the persistent disparities observed in [prostate cancer] outcomes given the strong inverse association between statin use and mortality observed in our study.”
The team concludes: “Beyond just treatment for existing comorbidities, our results provide support for the chemotherapeutic role of metformin and statins in preventing progression to lethal [prostate cancer] in men diagnosed [with] advanced [prostate cancer].”
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