Despite the usual excellent prognosis of differentiated thyroid carcinoma, some patients die because of disease. It has been speculated that lethal disease may have a better prognosis if patients are treated with extensive surgery plus 131I ablative treatment. We have analyzed a group of 223 patients with differentiated thyroid carcinoma treated under a uniform therapeutic protocol of surgery and followed for 3 to 17.7 years, in order to differentiate patients with a high and a low risk of mortality and the influence of therapy on survival rate.
The therapeutic protocol was as follows. If the diagnosis was papillary carcinoma, subtotal thyroidectomy was performed and cervical nodes were removed if they were suspicious for cancer. If the diagnosis was follicular carcinoma, a total thyroidectomy was performed. 131I was given in cases of patients who were more than 60 years old or who had extrathyroid disease or metastases in papillary carcinomas and in macroangioinvasive follicular carcinomas. In survival analysis, the event used as the end-point was death due to thyroid carcinoma and summarized by the Kaplan-Meier curve and the Mantel-Cox method.
We found three independent prognostic factors which determined mortality: over 60 years of age, tumor size larger than 6 cm and metastases. On the basis of these factors we identified two risk groups: a low-risk group (A), who had no risk factors, composed of 153 patients whose survival rate at 205 months was 100% and a high-risk group (B), who had one or more risk factors, composed of 55 patients whose survival rate at 213 months was 39.6%. Seventeen patients in this second group died from thyroid carcinoma. We therefore analyzed the effect of treatment in group B. Patients who had more extensive surgery had a similar survival rate to those who had less extensive surgery and 131I administration did not modify the survival rate.
These data support the idea that the identification of low-risk groups may facilitate a more rational approach to treatment of differentiated thyroid carcinoma, avoiding aggressive therapy in cases with a good prognosis.