Thyroid diseases as a sequelae following treatment of head and neck cancer

Aims: To evaluate the radiation-induced sequelae on thyroid gland and influence of concomitant chemotherapy.
Materials and Methods: This prospective study was carried out on 53 patients of head and neck carcinoma in the age group of 30-75 years (55.9 years). Patients were treated with external beam radiotherapy (52.8%) or concurrent chemo-radiotherapy with 5-flourouracil and cisplatinum (47.1%). The target volume included the thyroid gland, which received an average dose of 60 Gy in 30 fractions. Thyroid function tests were done at the start of radiotherapy. Follow up thyroid function tests were done on completion of radiotherapy treatment, at 3 months, at 6 months after treatment, and then every 6 months. Follow up ranges from 3-51 months (median: 27 months).
Results: Subclinical hypothyroidism was seen in 4 (7.5%) of the 53 patients. In three patients, the incidence was seen after a gap of 12 months and in one patient after a gap of 35 months. Of the four patients, three were of age ≤41 years and 1 was of age 66 years. In younger age group (30-39 years) patients, TSH shows statistically significant (P < 0.05) increase in TSH values. No significant difference was observed in radiation and chemo-radiation treatment groups (P > 0.10).
Conclusions: Subclinical hypothyroidism is an important sequelae seen in the treated patients of head and neck when thyroid is in the radiation field. The patients with age less than 45 years are more prone to develop hypothyroidism. Chemotherapy has not affected the incidence of hypothyroidism significantly. Also, the dose of radiation has not shown any statistically significant difference.