SAN FRANCISCO – In men with low-risk prostate cancer, vascular-targeted phototherapy (VTP) led to a significant reduction in subsequent conversions to radiation therapy or prostatectomy, compared with patients who underwent active surveillance. The latest results come at 4 years of follow-up, and confirm a reduction of risk seen in the original study at 2 years post treatment.
The new analysis was presented by Inderbir Gill, MD, in a late-breaking abstract session at the annual meeting of the American Urological Association.
Dr. Inderbir Gill
About half of men with low-risk prostate cancer start out with active surveillance, but 25%-60% of them will go on to radical therapy (RT) within the next 5-10 years. Put another way, about 70% of men with low-risk prostate cancer will undergo RT within a decade. This protocol is generally effective, but it comes at a cost: Sixty-six percent of men undergoing radiotherapy and 82% of men undergoing prostatectomy experience incontinence, and 4% and 20%, respectively, experience erectile dysfunction at 2 years.
That adds up to an unmet clinical need: Patients with low-risk prostate cancer would be well served by an alternative therapy that cuts the risk of RT. VTP, along with alternatives cryoablation and high-intensity ultrasound, were developed to meet that need.
The original, phase 3 trial enrolled 413 men at 47 centers in Europe. Participants could have one cancer core that was free of Gleason patterns 4 or 5 as long as its length was between 3 and 5 mm. The study also included men with two or three positive cores, as long as the length was less than 5 mm, but they were excluded if they had Gleason patterns of 4 or 5.The participants were randomized to active surveillance or VTP, which consisted of 4 mg/kg padeliporfin delivered intravenously. Optical fibers inserted into the prostate to target the treatment zone were activated by laser light.
In the VTP group, 185 men completed 24 months of follow-up, as did 174 in the active surveillance group. Overall, 69% of the participants achieved follow-up at 3 years, and 64% at 4 years. At 2 years, 6% of men in the VTP group went on to undergo RT, compared with 29% in the surveillance group (P less than .0001). There were no significant differences between the two groups with respect to incontinence or erectile dysfunction.
In the extension study, similar patterns were seen at 3 and 4 years. At 4 years, 53% of men in the active surveillance group had converted to RT, compared with 24% in the treatment group (hazard ratio, 0.31; 95% confidence interval, 0.21-0.45). The absolute difference in risk for conversion to RT between the two groups was 3% at year 1, 26% at year 2, 30% at year 3, and 29% at year 4.