The results of the trial, led by a team at the Institute of Cancer Research, London, and the Royal Marsden NHS Foundation Trust, will be presented at the American Society of Clinical Oncology (ASCO) annual meeting in Chicago.
"Our study has found that immunotherapy can benefit a subset of men with advanced, otherwise untreatable prostate cancer, and these are most likely to include patients who have specific DNA fix mutations within their tumours".
The world's leading expert on prostate cancer Professor Johann de Bono from the Institute of cancer research said: "We hope for a revolutionary cure, but they can't call it".
New prostate cancer drug Keytruda showed promising results in the first major clinical trial to test immunotherapy in some men with advanced prostate cancer.
The earlier trails conducted using immunotherapy in prostate cancer did not prove to be successful. Prostate cancer can develop when cells in the prostate start to grow in an uncontrolled way.
Eleni Efstathiou, MD, and colleagues at The University of Texas MD Anderson Cancer Center in Houston, studied 197 patients with M0HNPC randomly assigned to receive AA plus leuprolide (99 men) for 8 months or leuprolide alone (98 men).
De Bono said that while patients with DNA fix mutations responded to treatment, further investigation is still needed to confirm this.
Just 5 percent of men in the trial saw their tumours actually shrink or disappear after treatment, but the proportion was higher in a small group of men whose tumours had mutations to genes involved in repairing DNA, the researchers noted.
"Our examine has discovered that immunotherapy can profit a subset of males with superior, in any other case untreatable prostate most cancers, and these are most definitely to incorporate sufferers who've particular DNA restore mutations inside their tumours". It is an IgG4 isotype antibody that blocks a protective mechanism of cancer cells, and allows the immune system to destroy those cancer cells.
Only around 20% of cancer patients respond to immunotherapy and researchers do not fully understand why. It can work only for a few patients.
"The challenges we now face are how to predict in advance who will benefit, and how to make immunotherapy work for more people".
The researchers also said that some of the patients who had substantial responses to the treatment have tumors that may have mutations in the genes that control DNA fix, an important cellular process that maintains the genome. All participants had metastatic, recurrent prostate cancer and were treated with the anti-hormone therapy abiraterone and the steroid prednisone. Most prostate cancers are slow growing; however, some grow very quickly.