ESPE Abstracts

Background: Childhood cancer survivors (CCS) are at increased risk of developing secondary malignant neoplasms (SMN). Radiotherapy is one of the main risk factors, and secondary thyroid cancers (STC) are likely to occur among irradiated CCS.

Objective and hypotheses: To evaluate frequency, characteristics, and of STC in the cohort of CCS treated and in follow-up at the Istituto Giannina Gaslini.

Method: Survivors treated between 1975 and 2013 for a childhood cancer, and >2 years since elective end of therapies, were eligible. At follow-up all subjects had a clinical visit of the thyroid gland, and neck ultrasound evaluation was performed to subjects with a medical history of previous irradiation to fields potentially involving the thyroid. Fine needle biopsy was performed to subjects with >10 mm nodules. The cumulative risk of secondary thyroid cancer was calculated by Kaplan-Meir method.

Results: A total of 632 (312 males; 49.4%) CCS with a median follow-up since diagnosis of 10.1 years (range 22.2–38.9) were evaluated. Of these 155 (24.5%) received radiotherapy involving thyroid. 15 (2.4%) patients were diagnosed with STC between 5.1 and 18.4 years since diagnosis. All were of the papillary sub-type. Of these 11 (3.5%) occurred among males. STC were more likely to occur among the 155 CCS treated with RT involving the thyroid (n=12; 7.7%) than among those either not irradiated or irradiated in other fields (n=3; 0.6%) P<0.0001. Of the 3 not irradiated subjects with STC one was a female with Proteus syndrome; the second case lead to the diagnosis of MEN2b syndrome; while in the third case (Ewing sarcoma irradiated to the femur) no genetic predisposition was documented. The overall cumulative risk of developing SCT was 6.6% (95% CI 3.8–11.4). After stratification by radiotherapy exposure, the risk was 13.6% (95% CI 7.7-23.5) among CCS treated with thyroid radiotherapy and 1.9% (95% CI 0.7–6.8) among those not irradiated to the thyroid P=0.0003 (Figure).

Conclusion: Active surveillance for STC is recommended for survivors previously exposed to radiotherapy potentially involving the thyroid.