Technology ups treatment effectiveness without boosting this side effect, study finds
TUESDAY, Oct. 30 (HealthDay News) -- Among prostate cancer patients undergoing a high-tech form of radiation therapy, exposure to a higher amount of radiation over a shorter time span poses no added risk for impaired sexual function, new research reveals.
"For men getting a high dose of radiation in a shorter amount of time than is typical -- meaning getting higher doses per day for fewer days -- a loss of sexual function is the chronic side effect that concerns most," noted study co-author Dr. Eric Horwitz, a clinical director in the department of radiation oncology at Fox Chase Medical Center in Philadelphia.
"But we found that sexual function wasn't any worse than when patients got radiation in the conventional high-dose way," he said.
Horwitz and lead author Mark Buyyounouski, also at Fox Chase, were expected to present their team's findings at the annual meeting of the American Society for Therapeutic Radiology and Oncology, in Los Angeles.
The finding comes on the heels of work conducted at Fox Chase last year. That study indicated that high-dose radiation should be considered the first line of attack in combating prostate cancer, given that it appears to be the most effective way to limit the disease's spread.
The team focused on a form of radiation therapy called intensity-modulated radiation therapy (IMRT). According to the American Cancer Society, IMRT is a cutting-edge, 3-D form of high-dose radiation therapy. The treatment is delivered by a computer-controlled machine that moves around the patient to target diseased tissue while avoiding healthy tissue, thereby allowing for the safer use of higher doses of radiation.
In the current study, Horwitz and his colleagues tracked the IMRT radiation treatment outcomes of 155 men diagnosed with intermediate to high-risk prostate cancer.
Half the men were assigned to receive 2 Gray (Gy -- a measurement of radiation) in 38 sessions spread over seven and a half weeks.
The other half were exposed to 2.7 Gy in 26 sessions spread over just five weeks.
All the patients then completed questionnaires regarding treatment side effects six months, 12 months, and 24 months following radiation.
Older age, as well as poor sexual function prior to radiation, did increase the risk for sexual impairment after radiation treatment, the researchers said. However, they report no appreciable difference in sexual function between the men receiving the shorter course/higher dose regimen or the more conventional regimen.
"The key to curing more prostate cancer is to give higher does of radiation," observed Horwitz. "And over the last few years, more and more men have been getting higher dose radiation, because the radiation oncology community knows that dose matters and that low dose radiation is just not effective compared to high dose. And this study shows that we have the ability to give these high doses in different ways, and in all these ways, men do very well."
Horwitz said he and his colleagues plan to take the current research to the next level.
"We will build on this experience and go with even higher doses," he said, "to see how that impacts not only sexual function but urinary and bowel function as well."
Dr. Peter T. Scardino is chairman of the department of urology and head of the Prostate Cancer Program at the Memorial Sloan-Kettering Cancer Center in New York City. He described the finding as a small but important step toward developing shorter course/higher dose radiation therapies.
"This is the trend nowadays," said Scardino. "This is where this is going: toward a time when perhaps we will be giving radiation therapies all in a single day."
"Animal studies have already indicated that you may be able to achieve as much or more with a single dose of radiation than with a protracted course," Scardino noted. "So, the big question is, are you going to find more complications as a result of this kind of a shift in dosage? Now, cutting back from seven and a half weeks to five weeks is a slight move in this direction, but they found no difference in sexual side effects, and that's valuable. And I certainly think we'll be seeing a lot more research in this area."
There's more on radiation therapy for prostate cancer at the American Cancer Society.
SOURCES: Eric Horwitz, M.D., clinical director, department of radiation oncology, Fox Chase Medical Center, Philadelphia; Peter T. Scardino, M.D., chairman, department of urology, and head, Prostate Cancer Program, Memorial Sloan-Kettering Cancer Center, New York City; Oct. 29, 2007, annual meeting, American Society for Therapeutic Radiology and Oncology, Los Angeles
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