Radiation exposure does not significantly contribute to the risk of recurrence of Chernobyl thyroid cancer.

Abstract

Papillary thyroid carcinoma (PTC) in patients exposed to environmental radioiodine after the Chernobyl accident is thought to have a relatively aggressive clinical course. Long-term results of treatment are not well known, especially in comparison with sporadic PTC. The determination of risk factors for PTC recurrence in a controlled for baseline factors group of patients with radiation-related and sporadic PTC. Retrospective cohort study involving patients treated for PTC and followed-up in 1991-2008. Risk factors were assessed by stratified analysis using the proportional hazard model. Referral center-based. A total of 497 patients were enrolled. Patients exposed to radioiodine were 172 individuals with reconstructed individual radiation thyroid doses ranging 51-3170 mGy. Patients with sporadic PTC included 325 individuals matched to exposed patients for sex, age ± 5 yr and time to treatment ± 2 yr. Cancer recurrence. Nodal disease increased the recurrence rate (HR = 5.21; 95% CI = 1.63-16.7) while the presence of tumor capsule (HR = 0.17; 95% CI = 0.06-0.45) and, particularly, treatment according to the Revised American Thyroid Association Management Guidelines for Patients with Thyroid Nodules and Differentiated Thyroid Cancer significantly reduced it (HR = 0.16; 95% CI = 0.06-0.42). None of the tested variables interacted with radiation factor. PTC developing after internal exposure to radioiodine does not display specific risk factors for recurrence different from those in sporadic PTC. Common treatment approaches for patients with PTC should be recommended regardless of a history of radiation exposure.