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

The incidence of primary HT after IMRT for NPC continued to increase with time. The thyroid mean dose constraint was approximately 45 Gy. We recommended plan optimization objectives to reduce thyroid V45 to 0.5 and V50 to 0.35.