Radiation and risk for thyroid cancer: atypical findings of a community thyroid recall program.

Screening of 553 persons for thyroid disease by scan and physical exam was performed. Group I (245) had documented irradiation, with most (85%) receiving 300 R for lymphoid hyperplasia. Group II (308) had only a history of prior irradiation. Abnormal glands were found in 17 of 245 (7%) of Group I with 7 of 245 (3%) having nodular disease. No cancers were found in six of eight (75%) persons with nodular disease having surgery. Abnormal glands were found in 45/308 (14.6%) of Group II with 16/308 (5.2%) having nodular disease. Twelve of 16 (75%) with nodular disease from Group II had surgery and three thyroid cancers were found; in addition, one person from this group had a history of prior surgery for thyroid cancer. The incidence of thyroid cancer in Group I was 0%, Group II was 1.3%, and the combined incidence was 0.7%. The relatively low incidence of thyroid cancer observed is attributed to the relatively late average age at time of irradiation; 22 years for Group 1, 13 years for Group II.