Localized well-differentiated thyroid carcinoma: Survival analysis of prognostic factors and131I therapy

Background: Recommendations regarding therapeutic use of¹³¹I for patients with well-differentiated thyroid cancer remain controversial. Between 1969 and 1993, 1171 patients with papillary (including mixed) or follicular thyroid cancer were reported to the New Mexico Tumor Registry. Of these, 1075 cases (77.6% female, median age 41 years) were available for analysis of survival plots and previously recognized risk factors. Extent of operation was documented for 344 patients. Methods: One hundred twenty-seven (37%) patients underwent postoperative¹³¹I ablation. Median follow-up was 99 months. A proportional hazards model was constructed using age, gender, stage, histology, and use of radioiodine. The same variables plus extent of operation were examined in the smaller group. Results: Kaplan-Meier survival estimates at 12 years were 96.2% for patients younger than 45 years and 68.6% for those older than 45 years. Age, gender, and histology, but not stage, were important survival variables (P<.05). Adjusting for other risk factors, there was no apparent survival benefit associated with radioiodine following clinically appropriate thyroidectomy. Findings from the small group mirrored those of the large group. Conclusions: ¹³¹I may not be as efficacious as previously believed for patients with well-differentiated thyroid cancer confined to the neck.