Caution urged on new "breakthrough" cancer cure

29/07/2008

The media have been quick to claim that recent trials of the new drug, abiraterone, are a 'breakthrough cure for prostate cancer' - a condition causing the deaths of some 10,000 men every year. However, the drug has only been tested on 21 men so far - all with advanced, aggressive prostate cancer.

The good news is that all the men found significant tumour shrinkage, and there was a drop in tell-tale levels of a key protein produced by the cancer called prostate specific antigen in the majority of patients. Many also reported a significant improvement in the quality of their lives, and some were even able to stop taking morphine for pain relief when the disease to their bones.

However, it is still early days, and no patient has taken the drug for longer than two-and-a-half years - so side-effects and the impact on life expectancy cannot be measured. An advanced clinical trial involving 1,200 patients around the world is currently under way, with more trials likely later this year.

John Neate, Chief Executive of The Prostate Cancer Charity said: “These early trial results of abiraterone potentially represent the first significant advance in drug treatment of prostate cancer for some time. Advanced prostate cancer is very difficult to treat as, after a period of time, it stops responding to conventional ways of controlling the male hormone, testosterone, essential to the cancer’s continued growth.

"We look forward to the results of the larger trials already underway or being planned for this drug to prove its potential effectiveness for the thousands of men diagnosed with advanced prostate cancer every year in the UK.”

Until now, scientists and doctors had assumed that prostate cancer was driven by sex hormones such as testosterone, so treatments concentrated on preventing the testicles from producing testosterone. However, experts have now discovered that the cancer can feed on sex hormones from all sources, including supplies of the hormone produced by the tumour itself. So Abiraterone works by blocking production of the hormones throughout the whole body.

Professor David Webb, an expert in clinical pharmacology at the University of Edinburgh, said: "This drug clearly looks promising, but it is still at the early stages of clinical development. It will be crucial to look carefully at the balance between its benefits and harms, before drawing firm conclusions about the usefulness of this new drug.

"Important side effects often only emerge with the larger clinical studies that now need to be done."