I-131 and pediatric thyroid cancer post Chernobyl: Cause and effect?

The association between radiation exposure and subsequent thyroid cancer has been demon strated conclusively in epidemiological studies of children receiving external head and neck x-ray irradiation and in survivors of the atomic bomb exposures in Japan. Previous studies, however, have failed to demonstrate any causal association between diagnostic or therapeutic I-131 administration and thyroid cancer risk, although data regarding the pediatric population are scarce. New evidence emerging since the Chernobyl accident suggests that exposure to I-131 can cause thyroid cancer in children and adolescents, but further epidemiological studies are required to prove this hypothesis conclusively, Until the question is settled definitively, clinicians are urged to exercise due caution when considering the use of I-131 for diagnostic applications or when treating hyperthyroid states in individuals younger than age 20.