Laser-activated PCa therapy promising in phase III study

Researchers evaluate an experimental treatment called vascular-targeted photodynamic therapy in men with localized prostate cancer.

Results from a new late-stage trial could be good news for men with early localized prostate cancer, as researchers say they have a treatment that can kill the cancer without removing or destroying the prostate.

The non-surgical treatment utilizes WST11, a light-sensitive drug derived from bacteria found at the bottom of the ocean, and is called padeliporfin vascular-targeted photodynamic therapy (VTP). In the procedure, the drug is activated with a laser to destroy tumor tissue in the prostate, essentially killing the cancer cells while preserving healthy tissue.

The phase III trial, led by Mark Emberton, MD, of University College, London, included 413 low-risk prostate cancer patients. Of those, 49% of participants treated with WST11 went into complete remission, compared with 13.5% who received no treatment.

“There are many approaches being developed for early low-risk prostate cancer. Padeliporfin vascular-targeted photodynamic therapy is one such promising approach. High-intensity focal therapy, cryotherapy, focal MRI-directed laser ablation, new radiation techniques, and electoporation are some other potential focal therapy options that have been described,” Leonard G. Gomella, MD, of Jefferson Sidney Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, told Urology Times.

The trial involved 47 treatment sites from 10 different European countries, most of which were performing VTP for the first time.

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The results, published online in The Lancet Oncology (Dec. 19, 2016), further showed only 6% of patients treated with VTP required radical therapy compared with 30% of patients in the control arm who were under active surveillance. The authors said the odds of cancer progressing to a more dangerous stage were three times lower for patients on VTP, with the treatment doubling the average time to progression from 14 months to 28 months.

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"These results are excellent news for men with early localized prostate cancer, offering a treatment that can kill cancer without removing or destroying the prostate," Dr. Emberton said in a University College press release. "This is truly a huge leap forward for prostate cancer treatment, which has previously lagged decades behind other solid cancers such as breast cancer. In prostate cancer, we are still commonly removing or irradiating the whole prostate, so the success of this new tissue-preserving treatment is welcome news indeed."

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“The treatment is unique, appropriate in low-risk patients, and appears to have a good safety profile using the latest generation of the infused compound,” said Dr. Gomella, who was not involved with the study. “As with all new technologies, challenges are always present. Official FDA approval, insurance coverage, and cost issues issues when officially approved and how urologists apply the treatment will determine the long-term success of the approach.”

The European Medicines Agency is currently evaluating the University College approach, which could mean years before it can be offered on a wider scale. It’s unclear where and when the FDA would weigh in on the approval.

Dr. Gomella noted that while the current phase III study seems to be well done, the follow-up was relatively short at around 2 years, when most early prostate cancer studies need at least 5 and probably 10 years of follow-up to determine a beneficial outcome.

The phase III European trial was funded by STEBA Biotech, which holds the commercial license for the treatment, according to the press release.