Oral Oncol
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To investigate the rate and risk factors for developing hypothyroidism (HT) in nasopharyngeal carcinoma (NPC) patients treated with intensity-modulated radiotherapy (IMRT). ⋯ The incidence of primary HT after IMRT for NPC continued to increase with time. The thyroid mean dose constraint was approximately 45Gy. We recommended plan optimization objectives to reduce thyroid V45 to 0.5 and V50 to 0.35.