Six hundred patients with primary differentiated thyroid carcinoma had follow-up studies for a minimum of 15 years and a maximum of 45 years. Recurrence rate and death rate were significantly different in defined high-risk and low-risk groups of patients. These basic risk groups were defined by age and sex alone; low risk consisted of men 40 years of age and younger and women 50 years of age and younger whereas the high-risk group were older patients. Recurrence and death rates in patients at high risk were 33% and 27% while respective figures for patients at low risk were 11% and 4%. In more recent years these results have shown significant improvement. Basic risk group definition outweighed the effect of pathologic type, local disease extension, type of treatment, and site of recurrence or metastasis. For instance, radioactive iodine cured 70% of patients at low risk with metastatic disease but only 10% of patients at high risk. Less aggressive biologic behavior of thyroid cancer before the age of menopause implies that an estrogen-rich milieu may alter the effects of initiating and promoting factors in carcinogenesis. It also suggests that therapeutic trials of estrogen be undertaken in progressive metastatic differentiated thyroid cancer.

From 1961 to 1980 at the Lahey Clinic, 309 patients had initial surgical therapy for differentiated thyroid carcinoma. Review of this experience in comparison with previous decades revealed a progressive increase in the incidence of the disease in men, an increase in less extensive forms of the disease, an increase in use of bilateral subtotal thyroidectomy (77 % of patients), the discontinuation of use of prophylactic nodal dissection, and the progressive replacement of radical neck dissections by modified and limited neck dissections. In this series, with a median follow-up period of 13 years, 11% of patients had recurrence, and 7% died of disease. Determinants of outcome were shown to be risk groups as defined by age and sex, extent of disease (size of tumor and extent of extraglandular involvement), capsular invasion, blood vessel invasion, ability to remove all tumor at operation, and, to a lesser extent, pathologic type. Presence of nodes affected recurrence rate but did not have any deleterious effects on survival. Multifocal involvement did not appear to be an adverse prognostic factor. Treatment was successful in 73% of patients with nodal recurrences, in 53% with local recurrences, and in 27% with distant recurrences. Recurrences more often were treated successfully in low.risk patients than in high-risk patients. None of the deaths from local recurrence could have been prevented by initial total thyroidectomy. Recurrent nerve paralysis and hypoparathyroidism each occurred in only 1 patient (0.4%) who underwent bilateral subtotal or near-total thyroidectomy. We conclude that a selective approach using lesser opera-