Scientists have unveiled a new drug for prostate cancer which they say could help up to 80 per cent of patients with the aggressive and previously untreatable form of the disease.
Prostate cancer is the most common cancer in men, with 35,000 new cases and 10,000 deaths a year. Unlike breast cancer, there has been no significant advance in drug treatment for many years.
The new drug, abiraterone, works in a different way from existing treatments, shrinking the tumours of those with advanced forms of the disease. Taken orally as a pill, it has few side effects and has led to dramatic falls in prostate specific antigen (PSA), a blood marker for the cancer. However, experts warned that the research was at an early stage and had not yet shown that the drug extends survival.
Yesterday's announcement was triggered by the publication of the first clinical trial of abiraterone in 21 patients with advanced prostate cancer by the Institute for Cancer Research and the Royal Marsden Hospital in London. The small trial, known as a phase 1 study, was intended to test the safety of the drug but the results showed it was "spectacularly active", according to Johann de Bono, who led the research, published in the Journal of Clinical Oncology.
"This drug is highly effective," he said. "The tumours shrink, the pain goes away and the PSA levels fall. Some patients at the Royal Marsden have been on it for up to two years and eight months and are still doing well."
All the men in the study had very aggressive prostate cancer which was "exceptionally difficult to treat" and had an expected survival of about a year, said Dr de Bono, a consultant oncologist. They had been treated with surgery, radiotherapy or chemotherapy which had failed. "We hope that abiraterone will eventually offer them real hope of an effective way of managing their condition and prolonging their lives," he added.
A total of 250 patients have been treated worldwide, including 100 at the Royal Marsden, with similar response rates of 70 to 80 per cent. "We hope this drug will be approved in two to three years," Dr de Bono said. "There is no doubt in my mind that it is effective."
The drug is believed to work by inhibiting an enzyme which is critical to the production of the male hormone testosterone. Prostate cancer is known to be driven by testosterone and conventional treatment has been targeted at preventing its production in the testicles, as a chemical alternative to castration. Despite this, some men have had "hormone-resistant" cancers which have continued to grow The key discovery was that the cancers depend on testosterone manufacturedby the tumour itself, not by the testicles. Abiraterone blocks the process by switching off an oncogene, called ERG.
John Neate, chief executive of the Prostate Cancer Charity, said the discovery was an "exciting development" but needed confirming in larger trials.
'My symptoms virtually disappeared'
Simon Bush, former banker, 50
After being diagnosed with advanced prostate cancer in August 2005, Simon Bush had a course of intense radiotherapy and began three monthly injections of the anti-testosterone drug, Zoladex.
A year later, the news was grim. The cancer had spread to a number of sites in his skeleton and was starting to cause excruciating pain. He began a six-month course of chemotherapy but it failed to halt the cancer. Aged 48, married with two teenage children, he had been forced to give up his career as a banker and was told that life expectancy for patients such as him was about two years.
In April 2007, he was referred to the Royal Marsden from University College Hospital in London and started on abiraterone. "Within a week my PSA [prostate specific antigen] had dropped; within a month I had stopped taking painkillers. My symptoms virtually disappeared. In August 2006, I was told I had 24 months – well, my 24 months are up in three weeks and I am standing here feeling pretty fit. It has been absolutely phenomenal."
Mr Bush celebrated his 50th birthday in April – and his wife bought him a drum kit. "It is the worst thing possible for the bones, the back and the ribs. That is how much better I feel," he said
"I have had 15 months of near normality thanks to the drug. I have no doubt this drug gives hope to prostate cancer sufferers. My message to men is get checked out."