A major clinical trial has become the first to show benefits of immunotherapy in prostate cancer – for some men with advanced, otherwise untreatable disease.
Researchers showed that a subset of men who had run out of all existing options for treatment survived much longer than expected when taking immunotherapy.
Some 11 per cent of men with very advanced prostate cancer are still benefiting from the immunotherapy ‘checkpoint inhibitor’ pembrolizumab after a year – with many of them showing impressive remissions and prolonged disease control.
The international trial, led by a team at The Institute of Cancer Research, London, and The Royal Marsden NHS Foundation Trust, could lead to a subset of prostate cancers joining the list of cancers that can be treated with immunotherapy.
Of the 258 men on the trial with advanced prostate cancer receiving pembrolizumab, 38 per cent of men were still alive after a year and 11 per cent are still receiving the treatment a year after the trial began without seeing their cancer grow.
The research, presented at the American Society of Clinical Oncology annual meeting in Chicago, also revealed vital clues for how to pick out the subset of men who could benefit.
Previous trials of immunotherapy in prostate cancer had been unsuccessful – but the latest study looked back at the genetics of the tumours, and found there are some particular groups of patients that might benefit.
Overall, only 5 per cent of men in the trial saw their tumours actually shrink or disappear after treatment, but the proportion of responders was higher in a small group of men whose tumours had mutations to genes involved in repairing DNA.
The team at The Institute of Cancer Research (ICR) and The Royal Marsden believe that this subset of men with prostate cancer could benefit from immunotherapy, although more evidence is needed. They are planning a new trial of pembrolizumab specifically to assess whether it is effective in men who have DNA repair mutations in their tumours.