Some men with advanced prostate cancer could live for two years or more on immunotherapy

Some men with advanced prostate cancer who have exhausted all other treatment options could live for two years or more on immunotherapy, a major clinical trial has shown.

27 November 2019

Researchers found that a small proportion of men were ‘super responders’ and were alive and well even after the trial had ended despite having had a very poor prognosis before treatment.

The study found that one in 20 men with end-stage prostate cancer responded to the immunotherapy pembrolizumab – but although the number who benefited was small, these patients sometimes gained years of extra life.

The most dramatic responses came in patients whose tumours had mutations in genes involved in repairing DNA, and the researchers are investigating whether this group might especially benefit from immunotherapy.

The phase II clinical trial was led globally by a team at The Royal Marsden and the ICR, and involved 258 men with advanced prostate cancer who had previously been treated and become resistant to androgen deprivation therapy and docetaxel chemotherapy.

The study is published today (Wednesday) in the Journal of Clinical Oncology and was funded by the drug’s manufacturer Merck & Co., Inc., known as MSD outside the US and Canada.

Overall, 5 per cent of men treated with pembrolizumab saw their tumours actually shrink or disappear, while a larger group of 19 per cent had some evidence of tumour response with a decrease in prostate-specific antigen (PSA) level.

Among a group of 166 patients with particularly advanced disease and high levels of PSA, the average length of survival was 8.1 months with pembrolizumab.

Nine of these patients saw their disease disappear or partly disappear on scans. And of these, four were super-responders who remained on treatment at the end of study follow-up, with responses lasting for at least 22 months.

Personalising my treatment in this way, based on the genetic make-up of the tumour, essentially saved my life. I am grateful as I can enjoy spending time with my wife, four grandchildren and gardening.

Michael English, 74, patient on trial

Professor Johann de Bono, Consultant Medical Oncologist at The Royal Marsden and Regius Professor of Cancer Research at The Institute of Cancer Research, London, said:
“Our study has shown that a small proportion of men with very advanced prostate cancer are super responders to immunotherapy and could live for at least two years and possibly considerably longer.

“We don’t see much activity from the immune system in prostate tumours, so many oncologists thought immunotherapy wouldn’t work for this cancer type. But our study shows that a small proportion of men with end-stage cancer do respond, and crucially that some of these men do very well indeed.”

Michael English, 74, was treated with pembrolizumab at The Royal Marsden’s West Wing Clinical Research Centre in 2016. He said: 

“I was diagnosed with prostate cancer in 2005, and over a number of years I had hormone therapies, radiotherapy and chemotherapy, including treatment in research trials. Professor de Bono recommended pembrolizumab based on a genetic test and after only a few three-weekly cycles, we were astonished when scans showed that the tumour had become undetectable. I honestly thought the doctor had someone else’s scans when we were told the tumour had disappeared.
 
“Personalising my treatment in this way, based on the genetic make-up of the tumour, essentially saved my life. I am grateful as I can enjoy spending time with my wife, four grandchildren and  gardening.”