Prostate cancer patients who undergo a nonsurgical procedure to remove part of their prostate gland — using a kind of photodynamic therapy targeting the blood vessels — fare better in the long term than those under active surveillance, according to updated Phase 3 data.
The approach, called vascular-targeted photodynamic therapy, or VTP, uses a light-sensitive drug called WST11 that releases toxic, free radicals when activated. The drug is injected into the bloodstream and activated with a laser — coming from optical fibers inserted directly into the prostate — killing the surrounding cancer cells.
Trial results after four years of follow-up show that low-risk prostate cancer patients who receive this treatment are significantly less likely to require more aggressive treatments like surgery or radiation therapy. However, the rate of patients developing metastasis over the four years and the rate of patients who died from overall causes or from prostate cancer were similar among the two treatment approaches.
These results were recently shared in a presentation titled, “Four-year follow-up of a phase-3 prospective randomized trial of vascular-targeted phototherapy versus active surveillance for low-risk prostate cancer,” at the American Urologic Association Meeting in San Francisco.
In many cases of low-risk prostate cancer, active surveillance is an appropriate treatment option that reduces the consequences of over-treatment. However, it is not uncommon that treatment intervention is required.
Focal therapy — which removes a select part of the prostate gland — and active surveillance both share the goal of preserving prostate tissue and function by delaying or avoiding more aggressive treatment directed to the whole prostate gland.
The effectiveness of the two approaches, however, have not been compared in a prospective study.
To address this, the CLIN1001 PCM301 study (NCT01310894) was designed to compare the effectiveness and safety of focal therapy versus standard active surveillance in men with low-risk, localized prostate cancer.
In the trial, 413 participants were randomly assigned active surveillance or partial gland ablation using vascular-targeted photodynamic therapy.
Results published in 2016 showed that 49 percent of patients assigned to VTP achieved complete remission, compared with 13.5 percent in the control group.
Patients at that time had been followed for two years. During this period, only 6 percent of VTP-treated patients required radical therapy — complete removal or irradiation of the prostate — compared with 30 percent of the controls. In addition, the risk of disease progression was three times lower in the VTP group.
These results supported the European approval of VTP for low, but not very low, risk prostate cancer.
Now researchers have reported results of the trial after four years of follow-up. Specifically, they analyzed the percentage of patients who crossed over to radical therapy, as well as the metastasis-free, cancer-specific, and overall survival rates.
Men who received VTP had significantly lower crossover rates compared with active surveillance throughout the study: 7% vs. 33% after two years, 14% vs. 44% after three years, and 24% vs. 53% after four years.
This represented a reduction in the risk for radical therapy of 26% at two years, 30% at three years, and 29% at four years.
However, 99% of patients in both groups remained metastasis-free for the entire four years. None had died from prostate cancer over the four-year period, and only 2% in the VTP group and 1% in the control group died from any cause.
Overall, this study, the first and only randomized, controlled trial testing focal therapy for prostate cancer, supports the effectiveness of VTP at reducing prostate cancer progression and avoiding the need for more aggressive therapies.