Determinants of papillary cancer of the thyroid.

Determinants of papillary thyroid cancer were evaluated in a questionnaire-based case-control study from southeastern Sweden. A total of 104 cases, diagnosed from 1977 to 1987, and 387 randomly selected controls were included in the analyses. Female subjects with papillary cancer reported a work history as dentists/dental assistants, telephone operators, teachers, and day nursery personnel, and an occupational contact with chemicals and video display terminals more often than did controls. The 11 male cases more often reported working as mechanics and metal workers and having occupational contact with solvents. Other factors associated with increased risk for female papillary cancer were having private well water at the birth address; leisure time exposure to combustion smoke; low intake of cruciferous vegetables and seafood; and a family history of goiter, heart disease, biliary disorder, or female genital cancer. Diagnostic radiographic examinations, especially to the head, neck, or upper back/chest area, or repeated dental examinations, were also found to be associated with this form of cancer. With regard to the possible influence from hormonal factors among women less than age 50 years at time of diagnosis, an increased risk was found for a pregnancy soon after puberty. Tendencies toward a decreasing risk with increasing age at first pregnancy as well as an increasing risk with increasing number of pregnancies were found as well. Multiparity seemed to potentiate the effect from prior radiographic examinations.