Radiation-induced thyroid changes: A retrospective and a prospective view

Aim of the study: Incidental/therapeutic thyroid irradiation causes hypothyroidism and nodular disease. Increasing numbers of children are being cured of cancers by treatments that include radiation also involving the thyroid bed: these children warrant an early diagnosis and treatment of any radiation-related thyroid changes. Methods: In 1998 we retrospectively evaluated thyroid parenchyma/function in all patients irradiated between 1975 and 1997; thereafter, we prospectively evaluated all patients given thyroid irradiation by means of thyroid ultrasound and serum fT3, fT4, TSH and thyroglobulin. Results: Of 596 eligible patients, 468 agreed to the retrospective evaluation: 128/468 had one or more thyroid nodules, and 73 of these 128 had concomitant or previously untreated hypothyroidism, while 22/128 had a differentiated carcinoma. Another 144/157 patients treated between 1998 and 2004 were evaluated and any iatrogenic hypothyroidism was promptly treated: 19/144 had nodules, all smaller than 1 cm in diameter. The first patient group was studied retrospectively, so we have no precise record of the time of nodule occurrence or of their initial sizes. We found, however, that both the number of patients with nodules and the sizes of the nodules were significantly lower (p <0.01) in the prospectively studied group (after a median follow-up of 81 months) than in the retrospectively studied group. Among all the patients with nodules, significantly more females developed cancer than males (p <0.04). Conclusions: Early treatment for hypothyroidism and ultrasound evaluation of the parenchyma are needed to limit nodule onset and growth.