Mon 26 Sep, 2011 12:00 am BST
A prostate cancer drug trial has been stopped early, because the treatment was found to be so effective.
Doctors at the Royal Marsden Hospital cut short the phase III clinical trial of the drug - Radium 233 chloride - in patients with advanced prostate cancer, after they found that it significantly improved overall patient survival.
"It would have been unethical not to offer the active treatment to those taking placebo," Dr Chris Parker, a clinical oncologist, told the European Multidisciplinary Cancer Congress in Stockholm.
The drug, also known as Alpharadin - is a type of alpha-pharmaceutical which works by delivering minute quantities of damaging alpha radiation to secondary cancer cells in the bone.
The researchers decided to test Alpharadin in prostate cancer patients, as the disease spreads to the bone in nine out of ten men with the advanced form of the disease.
Radium also sticks to bone, the researchers said, especially new bone that is being made, which makes it 'highly effective' at delivering radiation to target cancer cells.
"It takes only a single alpha particle to kill a cell," said Dr Parker explained, "and collateral damage is minimised because the particles have such a tiny range - a few millionths of a metre (micrometres).
"So we can be sure that the damage is being done where it should be, to the metastasis, and very limited elsewhere."
The study involved 922 men with advanced prostate cancer. In all cases, the cancer had also spread to the patients' bones.
The patients received either standard treatment or Alpharadin plus standard treatment.
The study found that patients taking standard treatment plus Alpharadin had a 30 per cent lower rate of death compared to patients receiving standard treatment and a placebo (dummy drug).
Overall, the drug extended patient survival from around 11 months to 14 months.
Side-effects were reported to be minor, and included nausea, occasional diarrhoea and a 'very small effect on the bone marrow.'
"Although it has never been rigorously compared with chemotherapy, from observing patients in the clinic it is clear that patients tolerate it much better than they do chemotherapy," Dr Parker said.
The researchers now intend to submit the findings for regulatory approval.
"I would hope that the authorities will approve radium-223 as a treatment for bone metastases in advanced prostate cancer soon," said Dr Parker.
"Additionally, the drug could be used in many other types of cancers which metastasise to bone, regardless of the primary site. We believe that our trial may have paved the way for improvements in survival for very many cancer patients."