Vascular-Targeted Photodynamic Therapy ‘Effective’ For Low-Risk Prostate Cancer

Gleason pattern 3 prostate cancer might be treated using vascular-targeted photodynamic therapy

medwireNews: Vascular-targeted photodynamic therapy is an effective, well-tolerated treatment in men with low-risk localised prostate cancer compared with active surveillance, researchers suggest in The Lancet Oncology.

The phase III trial results suggest that men with treatment-naïve, Gleason pattern 3 disease “can be treated in a way that not only preserves their genitourinary function but also results in a lower progression rate, a greater chance of being declared disease-free, and a reduction in need for whole-gland radical therapy in the form of surgery or radiotherapy compared with active surveillance”, say the investigators.

During a median follow-up of 2 years, disease progression occurred in 28% of the 206 men given padeliporfin 4 mg/kg over 10 minutes followed by optical fibre insertion into the affected prostate zone and activation with laser light at 753 nm (150 mW/cm for 22 min 15 sec).

This compared with progression in 58% of the 207 men who underwent annual biopsies and prostate-specific antigen (PSA) measurement and digital rectal examination at 3-month intervals, giving a significant adjusted hazard ratio of 0.34, report Mark Emberton, from University College London in the UK, and team.

And the difference between the two groups was significantly in favour of photodynamic therapy for the individual progression criteria of more than three positive cores (11 vs 28%), Gleason pattern 4 or higher disease (24 vs 44%), cancer core length greater than 5 mm (12 vs 25%) and three consecutive measurements of PSA above 10 ng/mL (1 vs 7%).

Negative biopsy results at 2 years were reported for 49% of the men given vascular-targeted photodynamic therapy versus 14% of the men who underwent active surveillance (adjusted risk ratio=3.67).

The treatment was “well tolerated”, the authors write, although most patients had a mild or moderate severe adverse event during the procedure or in the days following treatment, including perineal pain in 15%.

Grade 3–4 prostatitis was more common with the treatment than surveillance (2 vs <1%), as was acute urinary retention (2 vs <1%) but erectile dysfunction affected 1% of men in each group.

“Padeliporfin vascular-targeted photodynamic therapy is a safe, effective treatment for low-risk, localised prostate cancer”, the team summarises, adding that it “might allow more men to consider a tissue-preserving approach and defer or avoid radical therapy.”

However, Stephen Freedland, from Cedars-Sinai Medical Center in Los Angeles, California, USA, describes the treatment in an accompanying comment as “not ideal” given that than half the patients continued to have residual cancer and more than a quarter progressed within 2 years.

Noting that quality of life was not improved in the men who were treated with vascular-targeted photodynamic therapy compared with those given active surveillance, he suggests that the results overall do not justify treatment for all men with low-risk prostate cancer.

The commentator therefore believes that while vascular-targeted photodynamic therapy is “a novel, interesting treatment” with “modest” tumour control and short-term side effects, it still “represents over-treatment of indolent disease or under-treatment of aggressive disease.”

“Invariably, a specific group will be found for which vascular-targeted photodynamic therapy is an ideal treatment, though for now such a group is not readily apparent”, he concludes.

References

Azzouzi A-R, 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. Lancet Oncol; Advance online publication 19 December 2016. DOI: http://dx.doi.org/10.1016/S1470-2045(16)30661-1

Freedland SJ. Low-risk prostate cancer: to treat or not to treat. Lancet Oncol; Advance online publication 19 December 2016. DOI: http://dx.doi.org/10.1016/S1470-2045(16)30651-9

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