Medullary thyroid cancer in Norway. A 30-year experience.

Eighty-four cases of medullary thyroid carcinoma were notified to the Cancer Registry of Norway in 1956-1978, representing 3.6% of all notifications of thyroid cancer in Norway during that period. The annual incidence of medullary thyroid carcinoma for the whole period was 0.89/million (0.57 in 1956-1971 and 1.47 in 1972-1978). Probably some cases were unrecognized in the early years and 1.47/million more accurately reflects the true incidence. More than 80% of the medullary thyroid carcinomas were presumably of sporadic type. Survival was significantly poorer than in the general population, and slightly less than in papillary thyroid cancer. Serum calcitonin assay was useful for primary diagnosis, follow-up, location of distant spread and discrimination between sporadic and familial disease. Basal calcitonin greater than 25 micrograms/l was accompanied by clinically demonstrable tumor in all but one patient. Elevated levels were repeatedly found in some long-term survivors, but among those with postoperative basal calcitonin greater than 2 micrograms/l, the 5-year mortality rate exceeded 50%.