Photodynamic Therapy Can Preserve Tissue in Low-Risk Prostate Cancer

Vascular-targeted photodynamic therapy with padeliporfin was significantly better than active surveillance over a 2-year period in men with low-risk localized prostate cancer, according to a new study. The treatment could allow men to avoid more radical therapy.

“Focal therapy and active surveillance are both tissue-preserving strategies,” wrote study authors led by Mark Emberton, MD, of University College London in the United Kingdom. “However, focal therapy differs from active surveillance in that it treats disease-by the process of selective tissue ablation-above a certain risk threshold and monitors disease below that threshold, because the latter is deemed to be clinically significant.”

The two therapies have not previously been compared directly in a prospective study. The new study randomized 207 men with low-risk localized prostate cancer to active surveillance, and 206 patients to vascular-targeted photodynamic therapy. Those patients had optical fibers inserted into the prostate to cover the desired treatment zone, and received 4 mg/kg padeliporfin infusion; activation of the therapy was done by laser light. The results were published online ahead of print in Lancet Oncology.

The median follow-up period was 24 months. At month 24, 58 patients in the photodynamic therapy group (28%) had disease progression, compared with 120 patients (58%) in the active surveillance group. This yielded an adjusted hazard ratio for progression of 0.34 (95% CI, 0.24–0.46; P < .0001).

Among the photodynamic therapy patients, 101 patients (49%) had a negative biopsy result at 24 months. In the active surveillance patients, only 28 patients (14%) had such a biopsy at that point, yielding an HR of 3.67 (95% CI, 2.53–5.33; P < .0001).

The therapy was generally well tolerated; the most common grade 3/4 adverse events included prostatitis in three patients (2%), acute urinary retention in three patients (2%), and erectile dysfunction in two patients (1%). Fifteen patients had serious retention of urine, including three patients deemed severe, but this resolved within 2 months in all patients.

“More research is needed to address unanswered questions, the principal one being the long-term effect of tissue-preserving treatment on control rates of prostate cancer,” the authors wrote. Still, “men who have low-risk, localized disease can now choose, on the basis of the evidence that our study has generated, how to approach tissue preservation.”

In an accompanying editorial, Stephen J. Freedland, MD, of Cedars-Sinai Medical Center in Los Angeles, wrote that the vascular-targeted photodynamic therapy is a novel and intriguing new option in this malignancy. “However, just like any new hammer, the trick is to find the right nail,” he wrote. “Until then, vascular-targeted photodynamic therapy either represents overtreatment of indolent disease or undertreatment of aggressive disease. Invariably, a specific group will be found for which vascular-targeted photodynamic therapy is an ideal treatment, though for now such a group is not readily apparent.”