Researchers found that for nearly 36,000 Taiwanese adults with shingles, the chances of developing cancer over the next several years were on par with national statistics.
Shingles - formally known as herpes zoster - is a painful condition caused by a reactivation of the virus that causes chickenpox, which is known as varicella-zoster. Once you have chickenpox, the virus goes into a dormant state and dwells in the body's nerve fibers.
Varicella-zoster most often reactivates in the elderly or people with weakened immune systems, including some cancer patients.
Thus, years ago, doctors thought people with shingles might be at increased risk of having an undiagnosed cancer, or of developing cancer in the future. But research since then has indicated that's not the case.
The new findings, published in the Canadian Medical Association Journal, offer more reassurance.
The study is also one of the first to focus on an Asian population. In Taiwan, people with shingles still undergo more cancer testing than those without the condition, according to Dr. Yi-Tsung Lin, of Taipei Veterans General Hospital.
"Our findings suggest that the extensive cancer survey is not necessary," Lin told Reuters Health in an email.
In the U.S., doctors have already stopped routinely looking for cancer in patients with shingles, according to Dr. Len Lichtenfeld, deputy chief medical officer for the American Cancer Society.
In theory, people with shingles could have an increased cancer risk: If having shingles is a sign that their immune defenses are down, then cancerous cells might be able to slip past the guards too.
And back in the 1970s, Lichtenfeld said, doctors thought people with shingles were more vulnerable to certain cancers. But then studies started to throw that idea into question.
"Now it's generally accepted that we should not be doing an extensive (cancer) workup on patients with shingles," Lichtenfeld said.
The main new piece from this latest study is the fact that it was done in Asia, according to Lichtenfeld - since past research on shingles and cancer has mostly come out of Western countries.
The findings are based on records from 35,871 adults treated for shingles between 2000 and 2008.
During that time, 895 people were also diagnosed with cancer at some point after their shingles diagnosis. That was a bit lower than the number that would be expected in the general population (905 cases).
The findings were similar when Lin's team looked at men and women separately, and at different age groups.
Lichtenfeld said that if people with a history of shingles are concerned about any new symptoms they are having, they should talk to their doctors.
But there's no reason that people newly diagnosed with shingles should be routinely evaluated for cancer - or undergo standard cancer screenings any more often than other people do.
Studies suggest that about 25 percent of people suffer from shingles at some point in their lives. It usually begins with a burning pain or itch in one location on one side of the body, followed by a rash of fluid-filled blisters.
Most shingles cases go away with medication, but occasionally people continue to feel nerve pain for months afterwards.
In 2006, the U.S. Food and Drug Administration approved a vaccine against shingles, made from a weakened form of the chickenpox virus, for adults older than 60.
SOURCE: http://bit.ly/Qg0hbq CMAJ, online September 17, 2012.