Early and Long-Term Thyroid Dysfunction in Patients With Head and Neck Squamous Cell Carcinoma After External Radiotherapy: Clinicopathological Risk Factors.

Background: To evaluate thyroid dysfunction(TD) among patients with head and neck squamous cell carcinoma (HNSCC) submitted to external radiotherapy (RT).

Methods: The study focused on early and long-term TD in 285 HNSCC patients treated with RT alone or combined with radiochemotherapy and/or surgery.

Results: A total of 156 (54.7%) patients presented TD during follow-up, 153 (53.7%) TD in long-term. Subclinical hypothyroidism (SCH) was the TD first identified in 43.5%; persisted in 68.5%, evolved to overt hypothyroidism in 21%, central hypothyroidism in 0.8%, returned to euthyroidism in 9.7%. TD first detection was 7.2 months after RT, 3.85 months for subclinical thyrotoxicosis, 17.77 months for SCH. Type 2 diabetes mellitus (DM2), metastatic lymph nodes, no tumor resection were TD risk factors. All patients with TSH ≥ 7.5 mIU/mL developed primary/SCH, 19.5% with TSH < 7.5 mIU/mL remained euthyroid at long-term follow-up.

Conclusions: Frequent monitoring of thyroid function is necessary in patients with HNSCC after RT, particularly with DM2, lymph node involvement, no surgical tumor resection.