The treatment could be an alternative for people who can't take the antiviral drugs usually used to treat shingles, says researcher Mohammed Suleiman, MD, a radiation oncologist at Hospital of Sion in Switzerland.
Each year in the United States, shingles strikes at least 850,000 people. Although children and younger adults can get it, most victims are over 60 and their immune systems have begun to wane. By age 85, one in two people will have had a bout. Other susceptible people are those with diseases that weaken the immune system or people who are taking medications that might suppress the immune system.
Shingles itself comes from reactivation of the chickenpox virus. The virus travels down nerve fibers to cause an itchy, painful skin rash that follows along the particular nerve in a band-like distribution called a dermatome.
When the rash goes away, the pain usually goes with it. But for 12% to 15% of people the pain remains. Doctors call this postherpetic neuralgia -- a truly debilitating condition that can last for months or years.
Some antiviral drugs such as Zovirax, Valtrex, and Famvir have been shown to reduce the duration of postherpetic neuralgia if begun within the first three days of the appearance of tingling or rash, Suleiman tells WebMD.
But not all people can take the drugs. People with kidney problems can't. Nor can a lot of elderly persons -- the very people whom shingles is most likely to strike, he says.
That's where radiation comes in.
Nerve Cells Zapped
Over the past 28 years, Suleiman and colleagues have administered radiation to 108 men and women considered at high risk of postherpetic neuralgia due to a serious rash and severe pain in the first month after shingles struck.
The people came in three times a week for two weeks; at each visit, the doctor zapped the affected nerve cells with a small dose of radiation.
Before radiation, 53 people complained of severe pain, 53 of moderate pain, and the rest of mild or noticeable pain.
In almost all, the rash -- and pain -- went away right away. Six months later, only 11% of the people had the lingering pain of postherpetic neuralgia.
In contrast, studies have shown that 20% to 25% of people treated with antiviral drugs have postherpetic neuralgia six months later, Suleiman says.
The findings were presented at the American Society for Therapeutic Radiology and Oncology's annual meeting.
Though 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, Suleiman says. "But we have not seen any secondary cancers, even in patients treated 28 years ago."
Phillip M. Devlin, MD, a radiation oncologist at Harvard Medical School in Boston, says the researchers "raise a fascinating phenomenon" that should undergo further testing.
But using radiation to treat conditions other than cancer in the United States is problematic, he adds.
"There is always that risk of radiation-associated [cancers], even with small doses," Devlin tells WebMD.
Why would radiation work? "It has anti-inflammatory, antipain effects," Suleiman says. "And it prevents viral replication."