By Amy Norton
NEW YORK (Reuters Health) - People who live in volcanic areas may have an elevated risk of developing thyroid cancer, a new study suggests.
Italian researchers found that between 2002 and 2004, rates of papillary thyroid cancer -- the most common form of thyroid cancer -- were twice as high in Sicily's volcanic region compared with the rest of the island.
Among people living in Sicily's Catania province, home to the active Mt. Etna volcano, there were 32 cases of thyroid cancer per 100,000 women per year, and six cases per 100,000 men. Across the rest of Sicily, those rates were 14 and three per 100,000, respectively.
The large majority of cancers were papillary thyroid tumors, a slow- growing form of the disease that accounts for most cases of thyroid cancer.
"The increase of thyroid cancer is striking in the volcanic area of Sicily -- more than the double in respect to the rest of the island," senior researcher Dr. Riccardo Vigneri, of the University of Catania Medical School, told Reuters Health in an email.
Because all volcanoes are not the same, it's not clear whether people living near any volcano might have an elevated risk of thyroid cancer, Vigneri said.
Further research should be done to track rates of thyroid and other cancers in these areas, according to Vigneri, who noted that about 500 million people worldwide live in a volcanic region.
He and his colleagues report their findings in the current issue of the Journal of the National Cancer Institute (NCI).
Located at the base of the neck, the thyroid gland produces hormones that help regulate heart rate, blood pressure, body temperature and weight. Thyroid cancer is relatively uncommon; in the U.S., for example, it is diagnosed in about 37,000 people each year, according to the NCI.
But the incidence of the disease has been on the rise in recent decades, in the U.S., France, Italy and elsewhere, Vigneri and his colleagues point out. Risk factors include iodine deficiency and exposure to high levels of radiation -- such as radiation treatment to the head and neck -- but beyond that, little is known about the types of environmental exposures that might contribute to the cancer.
According to Vigneri's team, it's possible that thyroid cancer rates were higher in Catania because of chemicals that are present in drinking water from the volcanic aquifer. "In many specimens of drinking water from the volcanic area we found that four metals and the natural radioactive compound radon 222 (were) increased over the maximum admissible concentration," Vigneri explained.
He added, however, that other explanations cannot be excluded.
More studies are needed to determine which, if any, drinking-water contaminants might be involved in the excess thyroid cancer risk, according to the researchers.
"If, as we suspect, the carcinogenic element is in drinking water," Vigneri said, "either filtration or dilution with water from (a) nearby non-volcanic environment is a potential way to lower the risk."
In most cases, the researcher noted, thyroid cancer is slow-growing and frequently found early, when treatment is usually successful.
According to the American Cancer Society, 97 percent of people diagnosed with the cancer are still alive five years later.
Initial symptoms of thyroid cancer can include a lump in the front of the neck, voice changes or hoarseness, swollen glands in the neck and difficulty breathing or swallowing -- though such symptoms more often have a cause other than cancer.
SOURCE: Journal of the National Cancer Institute, online November 5, 2009.