Radiotherapy in the management of thyroid cancer.

Surgery is the definitive and potentially curative treatment for the slow growing well-differentiated papillary and follicular carcinomas. Total (or near-total) thyroidectomy is required, together with excision of adjacent lymph nodes when involved, or a modified block dissection if there is extensive lymphatic involvement. Ablation of residual normal thyroid with radioactive iodine usually follows as this will permit subsequent whole-body I-131 scanning to exclude the presence of residual or metastatic disease. Normally such patients have an excellent prognosis and can be followed simply with serum thyroglobulin estimations. Occasionally therapeutic radioactive iodine is necessary to eradicate metastatic disease. The anaplastic carcinomas grow and metastasise with explosive rapidity. They are typically inoperable at presentation and have no ability to concentrate iodine. Prognosis is appalling with external beam radiotherapy providing only palliation. Medullary carcinoma is different again as it arises from the parafollicular or C-cells. Total thyroidectomy must be undertaken as these tumours may be multifocal; a central compartment neck resection is ideally undertaken at the same time, together with a formal block dissection if lymph node disease is found to be present. External beam radiotherapy is often required. These tumours can be inherited and produce the tumour marker calcitonin. The rarest group of thyroid cancer is the lymphomas. Like the anaplastic carcinomas, they grow very rapidly but, unlike the former, are radio-responsive. The additional use of chemotherapy is necessary when they are of advanced stage or demonstrate poor prognostic factors.