New laser-activated drug: shining a light on focal therapy

A new type of treatment that targets tumour tissue in the prostate has been shown to reduce the risk of low-risk cancers from progressing. The treatment, 'vascular targeted photodynamic therapy' (VTP, also known as TOOKAD), involves injecting a light-sensitive drug (padeliporfin or WST11) into the bloodstream and then activating it with a laser to destroy tumour tissue in the prostate.

Researchers at University College London led an international study of 413 men to test if this treatment is safe and effective. The men were randomly assigned to either receive VTP or active surveillance and were monitored for two years.

VTP is a form of focal therapy, a new approach that aims to target only the tumour and leave the rest of the prostate undamaged, unlike surgery where the whole gland is removed or radiotherapy where the entire area is irradiated. This is the first time that we have seen results from a large trial of a focal therapy. The trial was funded by STEBA Biotech, the company that owns the licence for this treatment.

Focal therapies could spare side effects of other treatments

The research, published in the journal The Lancet Oncology, found that only six per cent of patients treated with VTP required surgery or radiotherapy compared with 29 per cent of men on active surveillance. However, a third of men in the VTP group experienced serious side effects compared to only one in ten in the active surveillance group.

"In 1975 almost everyone with breast cancer was given a radical mastectomy," says Professor Mark Emberton, who led the study. "But since then, treatments have steadily 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."

Dr Matthew Hobbs, Deputy Director of Research at Prostate Cancer UK, said: "Focal therapy treatments like this one have the potential to offer a middle-ground option for some men with cancer that has not spread outside the prostate. By treating the cancer directly, rather than the whole prostate, this type of therapy could spare some men the long-term side effects of other treatments.

"However, as the researchers highlight in the study, we now need to determine exactly which cancers this type of therapy is most appropriate for, so that men can make an informed decision about which treatment to choose. Until we know the answer to this question, it is important that these results do not lead to the overtreatment of men with low-risk cancer, or the undertreatment of men at higher risk."

Further research needed into which cancers are most suitable

Since the trial began in 2011, diagnosis has improved through wider use of MRI and targeted biopsies, allowing men to be diagnosed more accurately. The men on the trial were classified as having low-risk cancers based on samples from TRUS biopsies, but these can often be inaccurate as the needles may miss some higher-grade cancer.

Further research will help us to better understand who might benefit from this therapy and how it can fit into the current treatment structure. Men classed as low risk are recommended active surveillance because their cancer is less likely to progress, so they can avoid or delay the side-effects caused by treatment.

For a man with a 'medium-risk' cancer, it can be difficult to decide whether to have treatment immediately or to keep a close eye on it. Focal therapy could help by offering a choice that can reduce the risk of the cancer spreading but with less serious side effects.

The researchers are in the process of publishing further results in men with higher-grade, Gleason 4 cancer cells. We are eagerly awaiting the results from this trial to understand how well it works for these men. The National Institute for Health and Care Excellence (NICE) began the process for developing guidance for this therapy earlier this year, but this has been delayed as it requires equipment that is not yet available in the NHS.

FAQs

• What is the treatment? A drug called padeliporfin or WST11 is injected through optical fibres inserted into the prostate, where it is then activated by a laser. It targets just the cancerous tissue without damaging the entire prostate.
• What are the benefits? It appears to reduce the risk of cancer progression compared to active surveillance, and so reduces the need for surgery or radiotherapy.
• What are the drawbacks? Many low-risk cancers will not progress and so treating these is unnecessary. This focal therapy does have side effects, so we need to be careful not to overtreat men.
• What do we still need to know? This trial followed men for two years, so we don’t know what the long-term benefit is. Only men classified with low-risk cancer were included in this trial, so we also need to better understand which men would benefit from this treatment.

The TOOKAD study was not funded or run by Prostate Cancer UK. VTP is currently being reviewed by the European Medicines Agency (EMA), so it's likely to be a number of years before it can be offered to patients in Europe. University College London Hospital offers some similar focal prostate cancer treatments, and men in the UK can be referred by their GP.