Metformin may protect against biochemical failure in localized prostate cancer

Use of metformin appears to confer a risk reduction in biochemical failure in men with localized prostate cancer treated with radical prostatectomy (RP) or radiation therapy (RT), a study has found.

The analysis included 1,449 patients undergoing RP (n=1338, 92.3 percent) or RT (n=108, 7.5 percent). All patients underwent assessments for metformin use, demographic/oncologic characteristics, and biochemical outcomes.

Of 1,449 patients, 148 (10.2 percent) used metformin at time of diagnosis while 1,301 (89.8 percent) did not. Users were significantly older, had higher body mass index (BMI), and had more aggressive disease (Gleason score >7).

Over a mean follow-up of 3.6 years, metformin users were less likely to experience biochemical failure at later timepoints. This trend was not observed on univariate analysis at 1, 3, and 5 years.

In multivariate analysis, metformin use yielded a significant protection against the risk of biochemical failure at 5 years and overall in both RP and RT groups. The relative risk reduction was 40 percent.

Animal and in-vitro studies have shown that metformin can inhibit prostate cancer progression by modifying the expression of tumour suppressor genes and oncogenes. The drug lowers hyperinsulinaemia and hyperglycaemia, both of which are potential risk factors for mortality in prostate cancer. These, among others, provide reasons to expect that metformin may have a potential role in delaying disease progression and improving clinical outcomes in men with prostate cancer. [Prostate Cancer Prostatic Dis 2015;18:110-121]