The results of a phase III clinical trial suggest that light therapy may be an effective, nonsurgical therapy for men with low-risk prostate cancer, after finding that almost half of study participants with the disease went into complete remission after treatment with the novel procedure.
In a study of more than 400 men with localized prostate cancer, researchers reveal that the new treatment - called vascular-targeted photodynamic therapy (VTP) - can kill prostate cancer cells, without damaging the healthy surrounding tissue.
Furthermore, VTP was found to significantly reduce the need for radical therapy, such as the removal or irradiation of the entire prostate.
Lead investigator Prof. Mark Emberton, dean of medical sciences and a consultant urologist at University College London in the United Kingdom, and colleagues recently reported their findings in The Lancet Oncology.
For men with localized prostate cancer - cancer that is considered low risk and has not spread beyond the prostate - "active surveillance" is often the first port of call. This is where the cancer is closely monitored through prostate-specific antigen (PSA) tests, digital rectal exams, or prostate biopsies, and it is only treated if it becomes more severe.
If the cancer does worsen, treatment may involve radical prostatectomy - which is the surgical removal of the prostate and nearby tissues - or radiation therapy. These procedures can pose a number of side effects, including bowel issues, urinary incontinence, and lifelong erectile dysfunction.
However, Prof. Emberton and colleagues suggest that VTP could reduce the need for such treatments by combatting prostate cancer in its early stages.
Complete remission for 49 percent of VTP-treated men
VTP was developed by researchers from the Weizmann Institute of Science in Isreal, in collaboration with biotechnology company STEBA Biotech.
The treatment involves the injection of a light-sensitive drug called WST11 - derived from bacteria found at the bottom of the ocean - into the bloodstream. Upon activation with a laser, the drug releases free radicals that destroy cancer cells in the prostate.
- Around 1 in 7 U.S. men will develop prostate cancer in their lifetime
- The disease is most common in men aged 65 and older
- While prostate cancer is serious, most men with the disease do not die from it.
For their phase III trial, Prof. Emberton and colleagues enrolled 413 men from 47 treatment sites across 10 European countries, all of whom had been diagnosed with early localized prostate cancer and were under active surveillance.
Of these patients, 206 were randomized to receive VTP, while the remaining 207 patients continued with active surveillance (the control group).
Patients were followed-up for 2 years, undergoing PSA testing and assessment of urinary and erectile functions every 3 months, as well as prostate biopsies at 12 and 24 months.
At the end of the 2-year follow-up, the researchers found that 49 percent of patients treated with VTP had entered complete remission, compared with only 13.5 percent of patients who received active surveillance.
Additionally, the researchers found that only 6 percent of men treated with VTP required radical therapy, compared with 30 percent of men in the control group. The team also reports that VTP-treated patients were three times less likely to have their cancer progress, and VTP was found to double the average time to progression from 14 months to 28 months.
Noting the side effects of VTP, the researchers report that some men experienced urinary and erectile problems, but these resolved within 3 months of treatment initiation. At 2 years, no significant side effects were present.
'Excellent news' for men with localized prostate cancer
The researchers believe that the findings of their phase III trial indicate that VTP is a promising nonsurgical approach to the treatment of localized prostate cancer.
"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," notes Prof. Emberton.
"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 1975 almost everyone with breast cancer was given a radical mastectomy, but since then treatments have steady improved and we now rarely need to remove the whole breast. 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."
Prof. Mark Emberton
Prof. Emberton points out that prostate cancer can now be identified using magnetic resonance imaging and targeted biopsies, meaning that it is possible to identify men who are most likely to benefit from VTP and therefore deliver more precise therapy.
"With such an approach we should be able to achieve a significantly higher remission rate than in the trial and send nearly all low-risk localized prostate cancers into remission," he adds.
"We also hope that VTP will be effective against other types of cancer - the treatment was developed for prostate cancer because of the urgent need for new therapies, but it should be translatable to other solid cancers including breast and liver cancer."
While VTP is currently being reviewed by the European Medicines Agency for the treatment of prostate cancer, the researchers say that it is likely to be a number of years before the therapy becomes widely available.