Low-Dose Radiation Numbs Lengthy Post-Shingles Pain
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Low-dose radiation could help relieve long-lasting post-herpetic neuralgia that often trails a painful herpes zoster outbreak, Swiss researchers reported.
“We think that radiation is at least as good as antiviral drugs in preventing post-herpetic neuralgia,” said Mohammed Suleiman, M.D., a radiation oncologist at Hospital of Sion in Switzerland. “This treatment,” he said, “could be an alternative for people who can’t take antiviral medications,” such as Zovirax (acyclovir) and Valtrex (valacyclovir).
Post-herpetic neuralgia endures in about 12% to 15% of people after shingles and can last for months or years, he noted at a poster presentation during the American Society for Therapeutic Radiology and Oncology meeting here.
Since 1975, Dr. Suleiman and colleagues have investigated using low-dose radiation directly to the rash to relieve acute pain and post-herpetic neuralgia. In the U.S. more than 800,000 people a year suffer attacks of shingles, triggered by the varicella zoster virus that caused chickenpox when they were youngsters.
In a retrospective study, 108 patients were studied in three treatment periods. From 1975 to 1983, patients received a total radiation dose of 1,250 centi-Gray; from 1983 to 2000, the dose was 1,500 centi-Gray. From 2000 to the present, the dose drifted between 225 and 640 centi-Gray.
Despite the lower dose in the last group, 89% of the patients irradiated within the first week of the acute attack were pain relief at three months. By one year, 93% were pain free, Dr. Suleiman said. If the patients came for treatment between a week and one month, about 88% were pain free at one year, he said.
Patients were treated three times a week for two weeks. At each visit, radiation was directed 5 cm to 7 cm into the ganglia with a fraction of the total radiation dose.
Before radiation, 53 people complained of severe pain, 53 of moderate pain, and the others of mild or noticeable pain. By six months, all but 11% of patients were pain free. Other reports, Dr. Suleiman said, indicate that lingering pain remains in about 20% of patients taking oral medication.
Although the radiation dose is only about one-tenth of that used to treat cancer, there is a risk of radiation-induced cancer developing years down the road, Dr. Suleiman noted. “But we have not seen any secondary cancers, even in patients treated 28 years ago,” he said.
Phillip M. Devlin, M.D., director of brachytherapy at Brigham and Women’s Hospital in Boston, a Harvard teaching hospital, said the researchers “raise a fascinating phenomenon” that should undergo further testing.
However, Dr. Devlin urged caution in using radiation to treat conditions other than cancer because ionizing radiation itself carries a finite risk of radiation-induced cancer.
Dr. Suleiman suggested that the radiation may work because it has anti-inflammatory, antiviral, and antipain effects. He noted that patients successfully treated with radiation and who achieved pain-free status did not have a recurrence of pain. He said he would welcome a controlled clinical trial.
Source: American Society for Therapeutic
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