MONDAY, Nov. 6, 2006 (HealthDay News) -- Men with prostate cancer who choose radiation therapy should consider high-dose radiation, because it appears to limit the spread of the cancer, U.S. researchers report.
Another study finds that long-term hormone treatment after surgery or radiation might extend patient survival.
Both studies were conducted by researchers at the Fox Chase Cancer Center in Philadelphia and were slated for presentation Monday at the annual meeting of the American Society for Therapeutic Radiology and Oncology, also in Philadelphia.
In the first study, researchers found that higher doses of 74 to 82 Gray (Gy -- a measurement of radiation) significantly reduce the risk that the cancer will spread, even 8 to 10 years after treatment.
That's important, because "the single greatest cause of death from prostate cancer is from distant metastasis," explained lead researcher Dr. Peter Morgan, a resident in the Radiation Oncology Department at Fox Chase. "Also, the greatest detriment in quality of life for prostate cancer patients comes from the symptoms of distant metastasis or the side effects of treatment with hormones," he added.
Cancers that appear five or more years after surgery or radiation are mostly due to cancer cells that were not killed during initial treatment, Morgan explained. "However, when we treat men with high-dose radiation, the latent wave of distant metastasis at eight to 10 years after treatment is reduced," he said.
In the study of 667 men with prostate cancer, Morgan's team found that over 10 years, the rate of the cancer spreading outside of the prostate was 16 percent for radiation doses less than 74 Gy, 7 percent for 74-75.9 Gy, and only 3 percent for doses greater than 76 Gy.
"If men choose radiation treatment for their prostate cancer, they should seek out a treatment center that will treat them with the higher doses of radiation," Morgan advised. "It's important for prostate cancer patients to ask and be aware of the dose of radiation they are going to get," he said.
One expert believes the study will help patients choose the radiation therapy that's best for them.
"This study helps clarify what radiation dose should be achieved," said Dr. Durado Brooks, the director of prostate and colorectal cancers at the American Cancer Society. "This helps establish a clear target of a dose that radiation oncologists need to achieve in order to help men have the most positive outcomes," he added.
Brooks is concerned about potential side effects of high-dose radiation, however. "Do these men at five years or 10 years have higher rates of erectile difficulty or higher rates of bowel or urinary problems?" he asked. "Quantifying that is important so men can make an informed decision," he added.
However, another expert said the findings are at odds with the results of prior randomized trials comparing high- and low-dose radiation.
"Randomized trials, so far, have not shown a benefit in distant disease-free survival. They have only shown a benefit in PSA recurrence," said Dr. Anthony D'Amico, the chief of radiation oncology at Brigham and Women's Hospital, Boston. PSA, or prostate-specific antigen, is the standard blood marker for tests aimed at gauging prostate cancer risk.
"The results of randomized trials will be the bottom line of whether distant metastases are prevented or not," D'Amico added.
In the second study, another team of Fox Chase researchers found that long-term hormone therapy after radiation treatment increased survival of men with locally advanced cancer.
In the study, 1,554 men with locally advanced prostate cancer received approximately four months of hormone therapy before and during their radiation treatments. After radiation treatment, some patients were given an additional 24 months of hormone therapy, while others received no further hormone therapy.
"At 10 years, the men receiving an additional 24 months of hormones showed significant benefit over those not taking additional hormone therapy," Dr. Gerald E. Hanks, the retired chairman of radiation oncology at Fox Chase Cancer Center, said in a prepared statement.
In fact, 45 percent of men with aggressive cancers who received the additional hormone therapy survived for 10 years, compared with 31.9 percent of the men who didn't get long-term hormone therapy.
Brooks noted that the best use of hormone therapy is not known and that recommendations for the length of therapy are inconsistent.
"I don't know if the findings of this study will lead all men to be recommended that they use the long-term hormone therapy, but I would say for men with aggressive prostate cancer, this makes a very strong argument that this should be considered the standard of care. And all men should be encouraged to consider this," he said.
However, the Fox Chase findings were contradicted by another study on hormone therapy released Sunday at the ASTRO meeting.
In that trial, a team at the Cleveland Clinic reviewed outcomes for 579 men treated for high-risk prostate cancer from 1996 to 2003. Patients received either more than six months of androgen-deprivation (hormone) therapy, less than six months of the therapy, or no hormonal treatment.
The researchers found that giving shorter-term therapy did improve patient survival, but that treatments lasting more than six months conferred no added benefit. "Treating current patients with shorter-term hormone therapy may not only be equally effective, but also improve their quality of life, due to a lesser degree of treatment side effects," radiation oncologist and study lead researcher Dr. Cliff Robinson said in a prepared statement.
D'Amico agreed that long-term hormonal therapy can have serious side effects, such as an increase in the risk of heart disease. "We need to find out if long-term hormonal therapy, while decreasing cancer deaths, is increasing some other potential cause of death," he said.
For more on prostate cancer, head to the U.S. National Cancer Institute.