Résumé
Seventy-five patients with tumors of the head and neck treated with either radiation therapy alone or combined with surgery or chemotherapy were studied prospectively to evaluate the effects of radiation therapy to the neck on thyroid gland between September 1986 and October 1992. All patients were serially monitored for thyroid function tests before and after radiation therapy. Radiation dose to the thyroid gland ranged from 35 to 60 Gy with a median dose of 50 Gy. Median follow-up time was 30 months with a range of 11 to 85 months. The incidence of thyroid dysfunction was 40%; forty-five patients (60%) euthyroid, 2 patients (3%) clinical hypothyroidism, 27 patients (36%) subclinical hypothyroidism and 1 patient (1%) hyperthyroidism. No thyroid nodules or thyroid cancer were detected in any patients. Thyroid dysfunction appeared earlier in patients who underwent surgery than in those patients treated with radiation therapy alone or combination of chemotherapy and radiation therapy (p=0.0013). By multivariate analysis, risk factors that significantly influenced a higher incidence of thyroid dysfunction were female sex (p=0.0293) and combination of total larygectomy and radiation therapy (p=0.0045). In conclusion, evaluation of thyroid function before and after radiation therapy with periodic thyroid function tests are recommended to detect thyroid dysfunction in time and thyroid hormone replacement therapy is recommended whenever thyroid dysfunction develops.