Metformin Active Surveillance Trial in Low-Risk Prostate Cancer

Area of Science:

• Oncology
• Pharmacology
• Clinical Trials

Background:

• Active surveillance (AS) is standard for low-risk prostate cancer (PCa), but progression occurs frequently.
• Metformin, an antidiabetic drug, shows preclinical and observational antitumor effects.
• Investigating metformin's efficacy to delay PCa progression in AS patients.

Purpose of the Study:

• To evaluate metformin's efficacy in delaying progression for men with low-risk PCa on AS.
• To assess the impact of metformin on progression-free survival (PFS) in this population.

Main Methods:

• The Metformin Active Surveillance Trial (MAST) was a phase III, multicenter, randomized, double-blind, placebo-controlled study.
• 408 men with low-risk PCa on AS were randomized to metformin (850 mg twice daily) or placebo for up to 36 months.
• Primary endpoint was time to progression (therapeutic/pathologic); PFS analyzed by Kaplan-Meier and Cox models.

Main Results:

• No significant difference in PFS between metformin and placebo groups (HR 1.09, P=.59).
• Metformin did not significantly improve negative biopsy rates at 36 months (41.0% vs 31.1%, P=.181).
• Obese patients (BMI ≥ 30) on metformin showed increased pathologic progression (HR 2.36, P=.0092).

Conclusions:

• Metformin did not reduce progression in men with low-risk PCa managed with AS.
• An increased risk of progression was observed in obese patients receiving metformin.
• Further investigation into metformin's adverse effects in obese PCa patients is warranted.