Endocrine Abstracts

Background: Radiotherapy (RT) with or without chemotherapy is a common treatment for head and neck squamous cell carcinoma (HNSCC) patients and it can cause adverse effects, including dysfunctions of thyroid. The aim of this study was to identify thyroid dysfunction among patients submitted to external RT for treatment of HNSCC, with serial evaluation of thyroid function.

Material and methods: This is a retrospective longitudinal study of the follow-up of thyroid function in 285 HNSCC patients treated with RT alone or associated with chemotherapy and/or surgery.

Results: 53.7% of 285 patients presented thyroid dysfunction, 44.9% of them maintained persistent dysfunction. The most common dysfunction was subclinical hypothyroidism (n =124), of which 68.5% remained with subclinical hypothyroidism, 21% evolved to overt hypothyroidism, 0.8% presented central hypothyroidism, and 9.7% returned to the euthyroid state at the end of follow up. The mean time after RT for the occurrence of subclinical dysfunction was 17 months whereas for overt evolution it was 24 months. Type 2 diabetes mellitus, bulky lymph nodes, and treatment with RT without surgery were seen as risk factors for thyroid dysfunction development. Regarding the risk of progression of subclinical hypothyroidism, a direct correlation with TSH level was observed: all patients with TSH ≥ 7.5 mIU/mL evolved to primary overt hypothyroidism or remained in subclinical hypothyroidism, whereas among those with TSH < 7.5 mIU/mL, 19.5% were euthyroid at the end of follow-up.

Conclusion: These data indicate the need for frequent monitoring of thyroid function in HNSCC patients treated with RT. Special attention should be given to the population at greater risk, such as those with type 2 diabetes mellitus, bulky lymph nodes, and treated with RT without surgery.