A randomized controlled trial evaluating the effect of low-dose chlormadinone in patients with low-risk prostate cancer: PROSAS study.

Objectives: This study was conducted to evaluate the effect of low-dose chlormadinone acetate, an antiandrogen agent, on the persistence rate of active surveillance in patients with low-risk prostate cancer.

Methods: The study was a multicenter, placebo-controlled, double-blind, randomized controlled trial conducted at 38 sites in Japan. Low-risk prostate cancer patients were randomly assigned to the chlormadinone group or the placebo group and the persistence rate of active surveillance was evaluated for 3 years.

Results: Seventy-one patients in the chlormadinone group and 72 patients in the placebo group were analyzed. The persistence rate of active surveillance [95% CI] at 3 years was 75.5% [62.5-84.6] in the chlormadinone group and 50.1% [36.7-62.2] in the placebo group, showing a significant difference between the groups (P = 0.0039). The hazard ratio [95% CI] of the chlormadinone group to the placebo group for discontinuation of active surveillance was 0.417 [0.226-0.770]. The chlormadinone group showed a significant decrease in prostate specific antigen level, testosterone level and prostate volume. The number of positive cores at 12 and 36 months biopsy was significantly lower in the chlormadinone group. The incidence of adverse events was 43.7% in the chlormadinone group and 12.5% in the placebo group. The most common adverse event in the chlormadinone group was constipation in 22.5%, followed by hepatobiliary disorders in 9.9%.

Conclusions: In patients with low-risk prostate cancer, low-dose chlormadinone showed a reduced number of positive cores and prostate volume, and an increased persistence rate of active surveillance (UMIN000012284).