Increased risk of certain second primary malignancies in patients treated for well-differentiated thyroid cancer.

Background: The objective was to evaluate the incidence of second primary malignancies (SPMs) in thyroid cancer patients compared to age- and gender-matched controls without thyroid cancer from the general population of the same region.

Methods: Tampere and Oulu University Hospitals treated 910 patients with well-differentiated thyroid cancer during 1981-2002. The Finnish cancer registry provided follow-up data for patients and controls (n = 4542) for an average of 16 years.