Radiation-induced hypothyroidism after IMRT for nasopharyngeal carcinoma: Clinical and dosimetric predictors in a prospective cohort study

Hypothyroidism (HT) is one of the most common late side effects described in literature after radiation to the cervical region for malignancies including nasopharyngeal carcinoma (NPC) [1–3]. The incidence of post-radiation HT varied in different reports, with most reported between 40% and 50% [4–15]. Half of the events occurred within 5years of follow up, with a peak incidence at 1–2years after radiation [4,6,7,9,13–17]. The major risk factors of HT identified included age [7,12,15,18], sex [2,9,10,12,18], the addition of chemotherapy [11,12], neck surgery [1–3,11,17], radiation dose [1,2,4,6–8,12,16], fractionation [7], pretreatment thyroid volume [4,6,10,16], the volume of thyroid irradiated [1,4–6,8–10,15] and the duration of follow up [9,12,13].

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