Medullary thyroid carcinoma is the most common cause of death in patients with multiple endocrine neoplasia (MEN) type 2A (MEN-2A) or type 2B or familial medullary thyroid carcinoma. We sought to determine whether total thyroidectomy in asymptomatic young members of kindreds with MEN-2A who had a mutated allele of the RET proto-oncogene could prevent or cure medullary thyroid carcinoma.

Methods
A total of 50 patients 19 years of age or younger who were consecutively identified through a genetic screening program as carriers of a RET mutation characteristic of MEN-2A underwent total thyroidectomy. Five to 10 years after the surgery, each patient was evaluated by physical examination and by determination of plasma calcitonin levels after stimulation with provocative agents.



Results
In 44 of the 50 patients, basal and stimulated plasma calcitonin levels were at or below the limits of detection of the assay (proportion, 0.88; 95 percent confidence interval, 0.76 to 0.95). Two patients had basal and stimulated plasma calcitonin levels above the normal range. Stimulated plasma calcitonin levels had increased but remained within the normal range in four patients. The data suggest that there was a lower incidence of persistent or recurrent disease in children who underwent total thyroidectomy before eight years of age and in children in whom there were no metastases to cervical lymph nodes.

Conclusions
In this study, young patients identified by direct DNA analysis as carriers of a RET mutation characteristic of MEN-2A had no evidence of persistent or recurrent medullary thyroid carcinoma five or more years after total thyroidectomy. A longer period of evaluation will be necessary to confirm that they are cured.