A "groundbreaking" new drug could treat up to 80% of patients with previously drug-resistant prostate cancer, according to a new study published in the Journal of Clinical Oncology.
Abiraterone could treat up to 10,000 British men diagnosed each year with the most aggressive and almost always fatal type of prostate cancer, results from a Phase 1 clinical trial suggest.
The study revealed significant tumour shrinkage and dramatic falls in prostate-specific antigen (PSA) levels (a protein associated with prostate cancer activity) in the majority of advanced prostate cancer patients who received the drug.
Lead researcher Dr Johann de Bono said the drug worked to block the generation of key hormones that drive the growth of prostate cancers.
"Clinical benefits included evidence of PSA falls and tumour shrinkage, which was observed in 70–80% of patients," he said.
"Abiraterone works not only in blocking the generation of these hormones in the testes, but also elsewhere in the body, including generation of hormones in the cancer itself."
Patients in the study were monitored for up to two-and-a-half years. Continued use of abiraterone meant they were able to control their disease with few side effects. A number of patients were able to stop taking morphine for the relief of bone pain.
"These men have very aggressive prostate cancer, which is exceptionally difficult to treat and almost always proves to be fatal," said Dr de Bono. "We hope that abiraterone will eventually offer them real hope of an effective way of managing their condition and prolonging their lives."
Dr de Bono said he envisioned that the drug will be available for general use from 2011, adding he hopes it "can become widely available."
Robin Wood, 65, from Wokingham near Reading, was diagnosed with aggressive prostate cancer in May 2007 and failed to respond to treatment. He said: "My prostate was very cancerous and I had only a one in five chance of being alive by the end of 2008.
"However, abiraterone radically changed that, with my health improving within a week of beginning the drug trial. I have just returned from the huge Round The Island Yacht Race, which is a testament to my better health."
The trial was undertaken by the Institute of Cancer Research and The Royal Marsden Hospital, and was funded by Cougar Biotechnology, Inc.
Abiraterone is now undergoing further clinical trials. It is being used in a 1,200-patient international study for the treatment of men with prostate cancer. Abiraterone is also being used to treat breast cancer in women through a Cancer Research UK funded trial.
Prostate cancer is the most common male cancer in the UK, with more than 35,000 new cases diagnosed annually. Around 10,000 men die of the disease every year, almost all of them from its castration-resistant form.
The Institute of Cancer Research Chief Executive Professor Peter Rigby said: "Today we can reveal a potential major advance in the treatment of prostate cancer. We hope with the generous contribution of the community we can continue to develop better treatments to combat many cancers."
Cally Palmer, Chief Executive of The Royal Marsden NHS Foundation Trust, said: "The results of this study show just how important abiraterone is set to become in the treatment of men with prostate cancer and highlights the national importance of funding pioneering cancer research."