Thyroid cancers in children, adolescents, and young adults with and without a history of childhood exposure to therapeutic radiation for other cancers.

Background: The thyroid is highly sensitive to the carcinogenic effect of radiation in children. We compared, in patients with and without earlier childhood radiation, the features of papillary thyroid cancer (PTC) diagnosed in later childhood through young adulthood.

Methods: Patients were from the Rhône-Alpes Thyroid Cancer Registry. Twenty-four patients (RAD group) had been treated by radiation therapy for nonthyroid neoplasms at the age of 8.0±6.0 years (mean±SD) and by surgery for PTC at the age of 17±6.4 years. They were compared with 413 patients with PTC but no radiation exposure (sPTC group, age 23±4.8 years). The two groups were subdivided into three subgroups, ages 8-14 (children), 15-20 (adolescents), and 21-29 years (adults) at time of PTC diagnosis, and compared to matched subgroups from 80 patients in the sPTC group (M-sPTC). Age in years at PTC diagnosis (RAD vs. M-sPTC) was 12±2 compared with 12±2 for children, 17±1 compared with 19±1 for adolescents, and 25±3.2 compared with 25±2.5 for adults. The matched subgroups had comparable pTNM, treatments, and follow-up. We compared the histopathological characteristics of the initial specimens and the outcome events.

Results: The RAD group and the sPTC group were similar in terms of age when PTC was diagnosed. RAD tumors had significantly more lymph node metastases (p=0.007) and a higher proportion of invasive pTN3 stage tumors (p=0.01). The adult RAD subgroup (n=8) was more likely to have lymph node metastases (p=0.004) and a higher proportion of invasive pT3N+ stage tumors (p=0.01) than the adult sPTC subgroup (n=316). During the 6.5 years of follow-up, there was no difference in the risk of cervical recurrence between the RAD group and the M-sPTC groups. Risk of cervical recurrence was also similar for tumors that were high risk (pT3N+).

Conclusion: Young adults with PTC associated with radiation therapy for nonthyroid neoplasms in childhood have a more aggressive initial presentation than young adults with sporadic PTC. The risk of recurrent disease in patients who received radiation in early childhood through adolescence and who developed PTC in late childhood through early adulthood is similar to those who did not receive radiation.