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New non-surgical treatment for early prostate cancer shows promise

Vascular targeted photodynamic therapy derived from bacteria on the ocean floor

Caroline White

Tuesday, 20 December 2016

A new non-surgical treatment for low-risk prostate cancer can kill cancer cells while preserving healthy tissue, reports preliminary research* published in The Lancet Oncology.

At the moment, men with low-risk prostate cancer are put under 'active surveillance' where the disease is monitored and only treated when it becomes more severe.

However, radical therapy, which involves surgical removal of the prostate or irradiating the whole gland, has significant long-term side effects, including erectile problems and incontinence.

The new treatment, 'vascular-targeted photodynamic therapy' or VTP for short, involves injecting a light-sensitive drug into the bloodstream and then activating it with a laser to destroy tumour tissue in the prostate.

The drug, WST11, is derived from bacteria at the bottom of the ocean. To survive with very little sunlight, they have evolved to convert light into energy with incredible efficiency.

This property has been exploited to develop WST11, a compound that releases free radicals to kill surrounding cells when activated by laser light.

The phase 3 trial, which involved 413 patients from 47 centres in 10 different European countries, found that around half (49%) of those treated with VTP went into complete remission compared with 13.5% in the comparison group.

VTP only caused short-term urinary and erectile problems which resolved within three months, and no significant side-effects remained after two years.

“These results are excellent news for men with early localised prostate cancer, offering a treatment that can kill cancer without removing or destroying the prostate," says lead author and consultant urologist at UCLH, Professor Mark Emberton.

He said that the treatment of prostate cancer had lagged behind that of other solid cancers such as breast cancer, and the new technique could potentially change that.

“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," he said.

In the trial, only 6% of patients treated with VTP needed radical therapy compared with 30% of patients in the comparison arm who were under active surveillance.

And the chances of the cancer progressing were three times lower for patients in receipt of VTP, while the treatment doubled the average time to progression from 14 to 28 months.

"New procedures are generally associated with a learning curve, but the lack of complications in the trial suggests that the treatment protocol is safe, efficient and relatively easy to scale up. We would also expect the treatment to be far more precise if we repeated it today, as technology has come a long way since the study began in 2011,” said Professor Emberton.

"We can now pinpoint prostate cancers using MRI scans and targeted biopsies, allowing a much more targeted approach to diagnosis and treatment. This means we could accurately identify men who would benefit from VTP and deliver treatment more precisely to the tumour,” he added.

“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 localised prostate cancers into remission.”

The researchers are hopeful that VTP could be used to treat other types of cancer, including those of the liver and breast.

VTP is currently being reviewed by the European Medicines Agency, so it is likely to be several years before it can be offered to patients more widely.

* Azzouzi A, Vincendeau S, Barret E, 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. December 2016. DOI: 10.1016/S1470-2045(16)30661-1

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