By Ed Edelson
WEDNESDAY, June 10 (HealthDay News) -- Men with moderately advanced prostate cancer who get hormone-blocking drugs after radiation therapy do better when the drug treatment is continued for two or more years after an initial six-month regimen, a European study has found.
The results pretty much mirror those of a similar American trial reported in May, said Dr. Eric M. Horwitz, acting chairman of radiation oncology at Fox Chase Cancer Center in Philadelphia, who led the group that did the U.S. study.
"We have long believed that longer-term hormone therapy is the standard of care," Horwitz said. "These studies support that belief."
The results apply to men whose cancer shows signs of growth but has not spread beyond the prostate gland -- perhaps a quarter of all cases of prostate cancer, Horwitz said.
Earlier studies in the United States and Europe established the value of radiation therapy followed by six months of hormone-blocking treatment in such cases, he said. The new studies were designed to determine whether continuation of drug therapy that blocks the cancer-promoting activity of the male hormone testosterone could improve those results.
Though the studies differed in size and length, their results were similar in most respects.
The European trial, reported in the New England Journal of Medicine, included 970 men who were assigned to radiation therapy followed by either six months or three years of hormone-suppressing treatment. The five-year death rate of men in the longer-treatment group was 15.2 percent, compared with 19 percent for those in the shorter-term treatment group.
The U.S. study, published in the Journal of Clinical Oncology, included 1,554 men who were followed for 10 years. The study found no significant difference in overall survival -- 51.6 percent for the short-term group, given four months of treatment, and 53.9 percent for the long-term group, treated for two years.
But it did find a difference among men who were alive and cancer-free after 10 years. The disease-free survival rate for the short-term group was 13.2 percent, compared with 22.5 percent for those treated longer.
Other measures, such as the spread of cancer to other parts of the body and greater growth of the malignancy within the prostate gland, were consistently better for men in the U.S. study who'd had the longer-term therapy.
Horwitz said that differences between the American and European results were not unexpected. Similar differences had been found in the studies that established the value of the radiation-plus-hormone therapy, he said. One possible explanation, he said, is that prostate cancers tend to be diagnosed at an earlier stage in the United States because of extensive screening programs.
Both studies reported the expected side effects of hormone-blocking therapy, including hot flashes, weight gain, osteoporosis and loss of sexual function.
"Some men get them and some do not," Horwitz said. "Over the last few years, there has been a lot of attention paid to these side effects, in the medical literature and in public awareness, and there has been more reluctance to use this therapy. These studies clearly identify a group of men who benefit from this therapy."
But Dr. Peter C. Albertsen, chairman of urology at the University of Connecticut Health Center, said that it's those side effects that should limit the use of longer hormone-blocking therapy to a specific group of men with prostate cancer -- those with "disease that is clinically evident on palpation [by touching] but with no evidence that it has spread outside the prostate," Albertsen wrote in an accompanying editorial in the journal.
He agreed that earlier forms of the cancer are more often detected in the United States than in Europe because of extensive screening programs. The side effects that balance the benefits of hormone-blocking therapy rule against extended therapy for those men, Albertsen said.
"For men with localized disease that is screening-detected, the equation is quite different," he said.
The U.S. National Cancer Institute has more on prostate cancer.