At the 10-year follow-up mark, 57% of those who got radiation alone survived, while 62% of those in the combination group were still alive, says William Shipley, MD, the Andres Soriano Professor of Radiation Oncology at Harvard Medical School.
The combination treatment made a difference not only in overall survival, but also in reducing deaths specifically from prostate cancer at the 10-year mark, he says. "In the ones with androgen deprivation therapy [hormone treatment], 4% died of prostate cancer," he tells WebMD. "With radiation alone, 8% did."
Men with intermediate risk of disease progression, as defined by several measures, benefited most from the combination treatment.
"If you have intermediate-risk prostate cancer and you are being treated with radiation, it will probably become standard treatment to have a short course of hormone treatment with that," Shipley says.
The study is published in The New England Journal of Medicine.
Radiation vs. Combination Therapy
Shipley and colleagues enrolled nearly 2,000 men with an age range of 47 to 91 who were judged to be at low, intermediate, or high risk of disease progression. The study began in 1994 and the median follow-up period was 9.1 years (half were followed longer, half less). All men had early-stage tumors when diagnosed.
The National Cancer Institute funded the study. It was conducted by the Radiation Therapy Oncology Group, which is administered by the American College of Radiology.
To assess the risk of disease progression, the researchers used several measures, including levels of PSA (prostate specific antigen, a protein made by the prostate gland and found in the blood), the Gleason score, and the stage of the tumor at diagnosis.
Most men were at intermediate risk.
The researchers assigned the men to the radiation-only group or the combination group. The combination group began taking the hormone therapy two months before the radiation began. They continued it during radiation, Shipley says. They took the hormone therapy for four months in all.
The hormone therapy reduces levels of male hormones, called androgens, which trigger the growth of prostate cancer cells.
When the researchers looked more closely at the risk groups, Shipley says, there were some important findings.
"If you looked at the subgroup that was in the low-risk category, there was no apparent benefit to the hormone therapy," he says. "It's safe to say it's hard to suggest these men need this treatment."
Adding the hormone therapy to those at high risk of progression appears beneficial, the researches write. However, they had an increase in deaths from prostate cancer at 10 years. The group that benefits most, Shipley says, is the group at intermediate risk of progression.
More men in the combination group had erectile dysfunction than those in the radiation-only group.
Before the treatment, 48% of those in the combination group and 54% of those in the radiation-only group said they could always or nearly always get an erection.
At the one-year mark, 21% of the combination group and 31% of those in the radiation group said that was still true.
''About half [in the hormone therapy group] got some form of hot flashes, and that can be bothersome," Shipley tells WebMD.
The radiation and the combination treatments are likely to be covered by a patient's insurance, Shipley says.
The study is an important one, says Stanley Liauw, MD, assistant professor of radiation oncology at the University of Chicago. He has researched combination therapy for high-risk prostate cancer.
He reviewed the study findings for WebMD.
Earlier studies have found benefit for combined treatment for men with locally advanced cancers, he says. But it wasn’t known if the combined therapy could help men with earlier cancers.
The new study is not the only one to address the question, he says. "However, this study is the largest, and with mature follow-up. It shows that four months of hormonal therapy does improve survival for men with intermediate-risk prostate cancer."
The study reinforces the need to individualize treatment, he says.
Liauw points out that the study looked at moderate radiation doses, the standard for the time period. More recently, higher doses have become standard and safer. He says studying the higher radiation doses with hormone therapy should be done.
Shipley agrees. The RTOG group has launched a study to look at combining hormone therapy with current radiation therapy.