"Radiotherapy Offers Option for Relief of Post Herpetic Neuralgia Pain Due to Shingles: Presented at ASTRO"
By Ed Susman
DENSVER, CO -- October 20, 2005 -- Low dose, focused radiation appears to prevent post-herpetic neuralgia in patients with shingles, researchers said here at the 47[th annual meeting of the American Society for Therapeutic Radiology and Oncology (ASTRO).
Shingles often occurs in the United States to elderly individuals. More than 800,000 people suffer attacks of shingles, caused by the same virus that caused chicken pox outbreaks in these same individuals when they were children.
Postherpetic neuralgia is a painful condition that affects the nerve fibers and skin. About 12% to 15% of individuals with shingles develop post-herpetic neuralgia, a condition that can last months or even years.
Current treatment involves pain control while waiting for the condition to resolve. Pain therapy can include multiple interventions, such as topical medications, analgesics, tricyclic antidepressants, anticonvulsants and various nonmedical therapies. Occasionally, narcotics may be required.
Dr. Suleiman said that some antiviral drugs such as acyclovir and valaciclovir can reduce the duration of post-herpetic neuralgia.
Dr. Suleiman and colleagues have experimented with use of low-dose radiation directly on the rash to relieve acute pain and post-herpetic neuralgia. In his retrospective study, he identified three periods of treatment. To date 108 patients have been evaluated.
From 1975 to 1983, patients received a total radiation dose of 1250 centi-Gray; from 1983 to 2000, the dose was 1500 centi-Gray. Since 2000, the dose has been between 225-640 centi-Gray. Patients were treated 3 times a week for 2 weeks. At each visit, radiation was focused 5 cm to 7 cm deep into the ganglia with a fraction of the radiation dose.
Despite the lower dose, patients who are irradiated within the first week of the attacks have achieved an 89% rate of pain relief at 3 months. By 1 year, 93% of patients are pain free, Dr. Suleiman said.
In patients who present for treatment after 7 days to 1 month of pain onset, about 88% are pain free at 1 year, he said in a poster presentation on October 18th.
Before radiation, 53 people complained of severe pain, 53 of moderate pain, and the rest of mild or noticeable pain. By 6 months, Dr. Suleiman said all but 11% of patients were pain free. He said that other reports indicate that lingering pain remains in about 20% of patients taking oral antiviral drugs.
While 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 said. "But we have not seen any secondary cancers, even in patients treated 28 years ago," he said.
Phillip M. Devlin, MD, Director of Brachytherapy, Brigham and Women's Hospital/Harvard Medical School, Boston, Massachusetts, United States, 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.
"We think that radiation is at least as good as antiviral drugs in preventing post-herpetic neuralgia," said Mohammed Suleiman, MD, Radiation Oncologist, Hospital of Sion, Sion, Switzerland. "This treatment could be an alternative for people who can't take antiviral medications."
Dr. Suleiman suggested that the radiation works because it has anti-inflammatory, anti-viral and anti-pain effects. He noted patients successfully treated with radiation and who achieved pain-free status have not had recurrence of pain. He said he would welcome a controlled clinical trail.
[Presentation title: Radiotherapy for Herpes Zoster (HZ) in the Acute Phase: A Retrospective Study with Long Follow-Up. Abstract 2333]
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