Incidence of hypothyroidism following multimodality treatment for advanced squamous cell cancer of the head and neck

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Abstract
The incidence of chemical hypothyroidism, as manifested by elevated thyroid stimulating hormone (TSH) levels, has been estimated to be as high as 25% after radiation therapy and 45% after radiation therapy and surgery to the neck for treatment of nodal metastases from squamous carcinoma of the head and neck. We prospectively evaluated 43 previously untreated patients seen in the Dana Farber Cancer Institute Interdisciplinary Head and Neck Service who were treated with aggressive combination chemotherapy in addition to standard surgery and/or radiotherapy. All patients were serially monitored for serum TSH, serum T4, and clincial evidence of hypothyroidism. Following cis‐platinum, bleomycin, and methotrexate chemotherapy and subsequent surgery and/or radiotherapy, decreased thyroid reserve appeared in 37% of patients at a median follow‐up of 9 months. Thirty percent of patients receiving radiotherapy alone and 43% of patients receiving surgery and radiotherapy developed elevated TSH levels. Only one patient developed clinical symptoms. Other patients were asymptomatic despite persistently elevated TSH levels. Abnormalities appeared within the first 4 months after completion of all therapy and were slowly progressive. The addition of combination chemotherapy does not appear to increase the incidence or severity of thyroid dysfunction following radiation therapy and surgery to the neck. In view of the extended survival seen in patients treated with interdisciplinary regimens, we recommend that all patients receiving irradiation to the neck – particularly those patients having neck dissections or total laryngectomies – have routine thyroid function studies performed following the cessation of treatment.