5α-reductase inhibitors (5-ARIs) have been shown to prevent prostate cancer in two RCTs but no work has evaluated their effect on those already diagnosed with low-risk prostate cancer. This single-institution retrospective cohort study evaluated the effect of 5-ARIs on pathological progression (Gleason score >6, maximum core involvement >50%, or > 3 cores positive on a follow-up prostate biopsy) in 288 men on active surveillance. Those taking a 5-ARI were compared with those not on a 5-ARI.

The following findings were reported after a median follow-up of 38.5 months:

• 93 men (32%) experienced pathological progression and 96 men (33%) abandoned active surveillance.

• Men taking a 5-ARI experienced a lower rate of pathological progression (18.6% vs. 36.7%; p = 0.004) and were less likely to abandon active surveillance (20% vs. 37.6%; p = 0.006).

• Lack of 5-ARI use was most strongly associated with pathological progression (hazard ratio: 2.91; 95% CI, 1.5 to 5.6).

The researchers conlcude from these findings that the 5-ARIs were associated with a  lower rate of pathological progression and abandonment of active surveillance., whilst acknowledging that these findings are limited by the retrospective design of their study and variable duration of 5-ARI therapy.