Men with advanced prostate cancer lived nearly four months longer on a new pill from Johnson & Johnson, according to keenly awaited study data that researchers said would change clinical practice.

Abiraterone, which could reach the market next year, provides a new option for men with an aggressive type of prostate cancer.

Its success underscored recent progress in tackling prostate cancer, the commonest cancer in men, and came after two other treatments - from Dendreon and Sanofi-Aventis - were approved this year.

In a large Phase III trial of men with prostate cancer who had previously received other treatment, including chemotherapy, those given the drug together with a low-dose steroid lived, on average, 14.8 months while those on steroids plus a placebo survived 10.9 months.

"That 3.9 months may not seem much but you have to understand that in the history of prostate cancer only four drugs have previously ever shown a survival benefit," said lead investigator Johann de Bono of Britain's Institute of Cancer Research, where the drug was originally discovered.

"This compares very favorably to Herceptin in breast cancer ... These results are likely to alter the standard of care for men with advanced prostate cancer."

The findings were presented at the European Society for Medical Oncology (ESMO) congress. Martine Piccart, the organization's president-elect, said the results of the 1,195-patient study were "very promising."

POTENTIAL BLOCKBUSTER

Doctors and investors already knew the clinical trial was successful, since a monitoring committee recommended last month that patients in the placebo arm be offered treatment because of a clear survival benefit. But the scale of the improvement was only made public at the cancer meeting on Monday.

"With that type of (survival) differential you are probably talking about a drug potentially with peak sales of over a billion dollars (per year)," said Damien Conover, an industry analyst at Morningstar.

J&J said it planned to file marketing applications for the new drug in the United States and Europe by the end of the year.

De Bono said patients taking abiraterone generally avoided unpleasant side-effects seen with chemotherapy, although they did have more mineralocorticoid-related side effects.

John Neate, chief executive of Britain's Prostate Cancer Charity, said the results offered "new hope" to men with advanced prostate cancer, a group of patients that can quickly run out of treatment options.

EARLIER DISEASE

De Bono said 2010 had been a landmark year for prostate cancer treatment, following the approval of Sanofi's Jevtana, a new chemotherapy, and Dendreon's pioneering Provenge cancer vaccine.

"We are increasingly making prostate cancer a chronic disease that the patient can live with by giving drug after drug," he said. "I think they (new drugs) will probably be given in series rather than added together."

Abiraterone was tested in patients who had metastatic castration-resistant prostate cancer, meaning their tumors were still growing despite receiving Sanofi's older chemotherapy drug Taxotere and hormone therapy designed to reduce testosterone.

In future, researchers plan to test abiraterone in men diagnosed with prostate cancer at an earlier stage of disease.