The occurrence of malignant thyroid lesions in patients after radioiodine treatment due to benign thyroid diseases

Abstract

Introduction: Radioiodine treatment (RT) of benign thyroid diseases is a well-known, safe, and effective treatment. In a group of patients after RT, who remained in long-term follow-up, sporadic cases of malignant thyroid lesions occurred. The aim of the study was to estimate how often it happened despite the exclusion of malignancy before RT.
Material and method: A group of 4314 patients (7438 person-years) underwent RT and subsequently were followed-up for 1-8 years (mean 20.69 months). Apart from thyroid function estimation, if needed, fine needle aspiration biopsy (FNAB) of the thyroid or neck focal lesions was performed based on ultrasonographic or clinical examination. Patients with pathological FNAB were analyzed and histopathologically verified.
Results: In 12 out of 4314 cases (0.27%) suspicious FNAB results were found. Suspicious thyroid lesion results were found in 9 patients (8 F, 1 M), aged 46-73 (average 56 years) followed up for 3-57 months after RT: papillary cancer in two patients, Hürthle cell tumour in one patient, and suspicious cells in two patients (with benign lesions on postoperative histopathology). Two patients refused surgery (a suspicion of papillary cancer in one case and suspicious cells in FNAB in the second case). A follicular tumour in FNAB was suspected in two cases (no data about the first, and the second with lung cancer was not operable). In the remaining 3 cases FNAB revealed lymph node metastases due to other cancers.
Conclusions: Malignant thyroid lesions in patients after RT due to benign thyroid diseases are seldom detected. However, periodical clinical and ultrasonographic evaluation is recommended.
(Pol J Endocrinol 2010; 61 (5): 454-457)