CALGARY, ALTA. — The incidence of well-differentiated thyroid carcinoma in Ontario, Canada, jumped 230% between January 1990 and December 2001, apparently because of an increase in small tumors in female patients, researchers reported during a poster session at the annual Canadian Surgery Forum.
“This phenomenon may be explained by the identification and resection of clinically relevant occult microcarcinomas incidentally found in women, who are more likely to see their primary care physician and undergo radiological investigations,” wrote Dr. Stephen Frederick Hall of the department of otolaryngology at Queen's University, Kingston, Ontario, and colleagues. “Alternatively, it may be that females have selectively been exposed to an environmental carcinogen or hormonal factor that has resulted in thyroid cancer.”
The researchers identified 8,100 cases of well-differentiated thyroid cancer from the Ontario Cancer Registry between January 1, 1990 and December 31, 2001. They compared the incidence of disease across the time period and obtained pathology reports from a random 10% of cases.
Incidence of the cancer increased 230% during that period, but the mean tumor size decreased, with significantly more small tumors (less than 2 cm) being resected in 2001 than in 1990. When male and female patients were compared, this effect was only seen in the female population.