MONDAY, Nov. 2 (HealthDay News) -- A brief course of hormone-blocking therapy can provide small benefits to a specific group of men who get radiation therapy for prostate cancer, a long-running study shows.
Ten-year survival was 62 percent in men with cancers graded as intermediate risk who got treatment that blocked their male hormone activity in addition to radiation therapy, compared to 57 percent of those who got radiation therapy alone, said Dr. Christopher U. Jones, a radiation oncologist at Radiological Associates of Sacramento, a member of the group who reported the results Monday at the American Society for Radiation Oncology annual meeting, in Chicago.
When biopsies were taken from men in the group, no traces of cancer were found in 78 percent of those having combined hormone-radiation therapy, compared to 60 percent of those who got radiation therapy alone.
The benefit is statistically significant but not huge, because "we weren't expecting large differences" in such cases, Jones said. And while study results already are incorporated in medical practice, it is not the final word on the issue, since the field is still evolving, he said.
"The standard of care in radiation therapy has changed since the study began in 1994," Jones said. "We can now localize treatment more so we give higher doses of radiation, 50 percent higher."
Even the definition of "intermediate risk" has changed over the years, he said. It is based on such factors as levels of prostate-specific antigen, a hormone produced by the gland, and Gleason score, a measure of the prostate's orderly structure.
"Since the study opened, we have more data and are better able to determine who is truly at low risk," Jones said. "Of the 2,000 we enrolled, we now know that 685 were truly low-risk, 1,068 were at intermediate risk and 226 were high-risk."
His summary of the results: "For the low-risk group, there is very little benefit in adding hormonal therapy. The most benefit is for those at intermediate risk, with high-risk patients in the middle."
In other words, "what we can show in this study is that patients can be spared hormonal therapy if they fit the modern definition of low-risk," Jones said.
That can be a big help, since side effects of hormone-blocking therapy include impotence and hot flashes, he said.
One reason why the study was undertaken was a growing use of hormonal therapy for men getting radiation treatment for prostate cancer, explained Dr. Anthony Zietman, a professor of radiation oncology at Harvard Medical School, incoming president of the radiation oncology society.
"There were some worries about the long-term consequences of hormone-deprivation therapy," Zietman said. "This study tells us that the majority of guys diagnosed with prostate cancer don't need hormone therapy at all."
Decision-making in such cases starts with a choice between surgery or radiation therapy. Physicians tend to prefer surgery for younger patients, but that decision can also depend on the choice of the patient, Zietman said. And there is some flexibility in the actual treatment to be given.
If radiation is the choice, treatment can then consist of a little bit of hormone therapy, for four months, or an increased radiation dose, he said.
"We know now that higher doses of radiation are better than lower doses," Jones said. "If higher doses of radiation are used, do you also need hormone therapy? A trial is just opening to ask that question."
Two other reports presented at the meeting revealed favorable results about proton therapy, in which prostate cancer is attacked by a beam of protons rather than X-rays. Physicians at the University of Florida in Jacksonville reported that proton therapy did not appear to have harmful effects to the urinary system, which had been feared. And a study at Loma Linda University in California found that a booster round of proton therapy reduced recurrence of prostate cancer in men who first had X-ray treatment.
Learn about prostate cancer diagnosis and treatment from the U.S. National Cancer Institute.
SOURCES: Christopher U. Jones, M.D., radiation oncologist, Radiological Associates of Sacramento, Calif.; Anthony Zietman, M.D., professor, radiation oncology, Harvard Medical School, Boston; Nov. 2, 2009, presentations, American Society for Radiation Oncology annual meeting, Chicago