Previous studies have demonstrated hormone treatment delays the progression of prostate cancer and makes patients feel better, but until now there has been little solid evidence that the approach can save lives.
Death rates from prostate cancer have dropped by one-third in North America and by 20 percent in Europe since 1990 among men aged 65 to 74, according to Sir Richard Peto, who presented findings analyzing evidence from 40 years of prostate cancer research at Europe's biggest cancer conference Monday.
Prostate cancer kills more than 200,000 men annually worldwide. About 190,000 new cases of prostate cancer are diagnosed in the United States every year, and about 30,000 men died of the disease in 2002, according to American Cancer Society statistics.
Earlier detection and better surgery and radiotherapy have helped reduce death rates. But Peto, a professor of medical statistics at Oxford University who has conducted many of the key studies evaluating cancer treatments and risks, said the lifesaving benefit of hormone treatment has been vastly underrated.
He reported the accumulated evidence from several studies on hormone treatment involving a total of 5,000 men. Taken separately, the studies were inconclusive, but analysis of them all together showed that when doctors gave hormone treatment immediately instead of waiting until the disease progressed, the risk of dying from the disease within 10 years dropped by one-third.
"This definitely shows that hormone treatment works," said Dr. Michael Thun, chief of epidemiology at the American Cancer Society.
"There is still debate about how much of the decline in (national) death rates is due to treatment and how much is due to earlier detection through screening, but the evidence for the importance of treatment in these declines is getting stronger," said Thun, who was not involved in the research.
The findings follow similar success reported in breast cancer, where death rates in middle age have fallen by about one-third since 1990.
Breast cancer, in most cases, is driven by the female hormone estrogen, while prostate cancer is most often driven by the male sex hormone, testosterone.
Even after successful surgery, a few cancer cells may remain undetected nearby or in distant parts of the body. Radiation therapy can kill off cancer cells near the tumor site.
Undetectable cells that have traveled elsewhere in the body can be attacked by chemotherapy in breast cancer, but not in prostate cancer. Hormone therapy prevents the fragments from being stimulated into becoming more dangerous by the body's own sex hormones.
"Hormonal treatments have been available for ages, but they've involved really unpleasant things like being castrated. For that reason, doctors have been reluctant to use it and have mostly given it only in advanced prostate cancer," Peto said.
"And the hormonal drugs that used to be available were pretty horrible. But now the drugs are a lot nicer than they were and they are getting better all the time."
The more recent drugs, such as Casodex, seem to produce the desired effect, generally without impotence, he said.
"Back in the early '80s, there was a widespread belief that hormonal treatment just didn't work for breast cancer and prostate cancer," Peto said. "There was a general feeling that it may somewhat delay recurrence but that it was going to do little or nothing for survival. It's just not true."
"Hormonal treatments for these things have probably saved more lives than any single cancer drug," Peto said.
The chances of surviving prostate cancer vary widely across regions and depend on how early the tumor is detected.
By Emma Ross