The prospective trial PCM301 randomized 413 men with low-risk prostate cancer to partial gland ablation with vascular-targeted photodynamic therapy (n=207) or active surveillance (n=206). Two-year outcomes were reported previously. Here we report four-year rates of intervention with radical therapy and further assess efficacy with biopsy results.

Prostate biopsies were mandated at 12 and 24 months. Thereafter, patients were monitored for radical therapy, with periodic biopsies performed according to standard-of-care in each institution. Efficacy of ablation was assessed by biopsy results overall and 'in-field' (treated lobe, or lobe with index cancer).

Conversion to radical therapy was less likely in the ablation cohort than the surveillance cohort: 7% versus 32% at two years, 15% versus 44% at three years, and 24% versus 53% at four years (HR 0.31, 95% CI=0.21-0.46). Triggers for radical therapy were similar in the two arms. Cancer progression rates overall and by grade were significantly lower in the ablation cohort (HR 0.42, CI = 0.29-0.59). End-of-study biopsy results were negative throughout the prostate in 50% after ablation versus 14% after surveillance (risk difference 36%, CI 28%, 44%) and Gleason 7 or higher cancer was less likely (ablation, 16%; surveillance, 41%). In-field biopsies contained Gleason 7 cancer in 10% after ablation versus 34% after surveillance.

In this randomized trial of partial ablation for low-risk prostate cancer, photodynamic therapy significantly reduced the subsequent finding of higher-grade cancer on biopsy. Consequently, fewer patients converted to radical therapy, a clinically meaningful benefit that lowers treatment-related morbidity.