Radioiodine and radiotherapy in the management of thyroid cancers.

Radioiodine is an important adjuvant treatment in the management of resectable papillary and follicular thyroid cancers in all patients except those with the best prognostic features. External radiation is also an important adjuvant therapy in these patients, especially those with tumors that extend beyond the thyroid gland and invade the trachea, esophagus, nerves, and blood vessels; it is especially important in treating patients whose tumors do not concentrate radioiodine. Radioiodine may be curative in patients with microscopic distant metastases demonstrated by radioiodine scanning. Even unresectable primary papillary and follicular cancers may be eradicated by combined therapy with radioiodine and radiotherapy. Radioiodine plays no significant role in the treatment of medullary or anaplastic thyroid cancers, but external radiation may eradicate microscopic thyroid bed or nodal disease when persistent disease is indicated by elevated calcitonin levels in medullary thyroid cancer patients. Anaplastic thyroid cancers are usually unresectable and are not eradicated by conventional radiotherapy or by any of the novel radiation techniques, with or without chemotherapy. In all types of thyroid cancer, external radiotherapy may produce beneficial palliative results in patients with distant metastases, but the use of radioiodine should always be explored in papillary and follicular thyroid cancer patients.