Scientists are bringing prostate cancer treatment into the 21st century with a new method that uses lasers and ocean bacteria to target the disease rather than surgery.

A study published in The Lancet Oncology describes a process called vascular-targeted photodynamic therapy, also known as VTP, that involves injecting a light-sensitive drug into the patient’s blood and then using a laser to activate the drug, which then kills cancerous tissue. The method was developed by the Weizmann Institute of Science in Israel and company STEBA Biotech before University College London researchers led trials on prostate cancer patients. That light-sensitive drug, called WST11, is derived from bacteria that lives at the bottom of the ocean and survives with low levels of sunlight by efficiently converting light into energy.

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The researchers collected data from more than 400 patients with “low-risk, localised prostate cancer,” previously untreated, at a few dozen European medical centers between 2011 and 2013. Half of those men received the light therapy, while the other half were simply monitored. When the researchers followed up with the patients about two years after their treatment, only about 28 percent of those who were treated with the light therapy had seen a progression in their disease, as compared to more than half of the group of men who were not treated in that way.

The scientists saw other differences in outcomes too: According to the study, almost half of the VTP group were in remission two years after their treatment, compared to only 14 percent of the non-treated men in the other group.

In addition to its effectiveness, the new treatment can kill the early-stage cancer without damaging or removing the prostate and healthy tissue, unlike the surgery and irradiation used to treat higher-risk cancers. Those two latter treatments may also cause long-term erectile issues and incontinence. The study notes, however, that the most common side effect in the VTP group was difficulty urinating, but it occurred in just 15 of the more than 200 men who were treated and it “resolved” within a couple of months.

“This is truly a huge leap forward for prostate cancer treatment,” lead investigator Mark Emberton, of the University College London, said in a statement from that institution. “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.”

One of the first patients with low-risk prostate cancer to be treated with VTP was a man in his 60s the university identified as Gerald. After taking part in the trial, he said, “Some men prefer to delay treatment, but I couldn’t live with the fear of the cancer spreading until it either couldn’t be treated or needed a treatment that would stop me living a normal life. … I’m now cancer-free with no side effects and don't have to worry about needing surgery in future.”

The benefits of the new therapy may not stop at prostates, however. Emberton expressed hope that it would be useful in killing other types of cancer as well. “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,” he said.

It may be some years before the treatment becomes readily available to patients, as it is under review with the European Medicines Agency.

Source: Emberton M, Azzouzi A, Vincendeau S, et al. Padeliporfin vascular-targeted photodynamic therapy versus active surveillance in men with low-risk prostate cancer (CLIN1001 PCM301): an open-label, phase 3, randomised controlled trial. The Lancet Oncology. 2016.

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