New drug shows promise for advanced prostate cancer patients
New results from a phase II clinical trial of the prostate cancer drug abiraterone suggest that it may help men with advanced disease who have tried standard treatments.
However, a Cancer Research UK clinician cautioned that there were still questions to be answered from ongoing studies about how best to use the drug.
Abiraterone was discovered in the Cancer Research UK Centre for Cancer Therapeutics at The Institute of Cancer Research (ICR) and is taken once a day as four pills.
The latest trial, which was led by the ICR and the Royal Marsden NHS Foundation Trust, is the first to investigate the drug in men with such advanced prostate cancer.
A total of 47 men were recruited for the trial, all of whom had late-stage castration-resistant prostate cancer, which means that their disease was advanced and their tumours were no longer responsive to androgen deprivation therapy. In almost all cases, the men's cancer had spread to their bones.
All of the participants had already received hormone therapy and the chemotherapy drug docetaxel, but were no longer responding to those treatments.
By the end of the study period, researchers found that around three-quarters of men had experienced a drop in levels of prostate specific antigen (PSA), which is often raised in men with prostate cancer and can be used to measure disease activity.
In around half of the men, PSA levels fell by at least 50 per cent, while three-quarters of participants also had a drop in the number of tumour cells circulating in their blood.
Three years after the start of the trial, five of the patients were still taking abiraterone and benefitting from the treatment.
Chief investigator Dr Johann de Bono, from the ICR and the Royal Marsden, commented: "Docetaxel is an important drug, but it extends life for an average of just two to three months, so there is a desperate need to improve treatment options for late-stage prostate cancer patients.
"In this trial, abiraterone shrank or stabilised men's cancers for an average of almost six months, which is a very impressive result."
Lead researcher Dr Alison Reid, also from the ICR and the Royal Marsden, noted that the drug tended to cause only mild side-effects, which were easily treated.
She added: "This is the first time the drug has been tested in prostate cancer patients with such advanced disease, who have already tried all the other effective treatments available to them."
Professor Malcolm Mason, Cancer Research UK's prostate cancer expert at Cardiff University School of Medicine, commented: "These early results are extremely exciting but there's a lot more work needed to establish what abiraterone's place will be in treating men with prostate cancer.
"We eagerly await the results of ongoing studies of abiraterone in clinical trials as they will give us the most definite indication of what impact this drug might have in men with advanced prostate cancer."
Dr Sally Burtles, director of centres at Cancer Research UK, added: "We're delighted that abiraterone is continuing to show promise in men with an advanced form of prostate cancer.
"Driving new treatments into clinical trials has been a key focus of the charity for many years and we are pleased to see the impact that this investment is having on people with cancer today."
Following the promising phase II trial findings, which are published in the Journal of Clinical Oncology, abiraterone is now being taken forward into large-scale trials.
A phase III trial involving men who have already received chemotherapy has now finished recruiting and is now underway, and a separate phase III trial involving men who have not yet tried chemotherapy is currently recruiting patients.
Abiraterone is also the focus of an early clinical trial by Cancer Research UK for women with advanced breast cancer.
- Reid, A. et al (2010). Significant and Sustained Antitumor Activity in Post-Docetaxel, Castration-Resistant Prostate Cancer With the CYP17 Inhibitor Abiraterone Acetate Journal of Clinical Oncology DOI: 10.1200/JCO.2009.24.6819