Can minimally invasive follicular thyroid cancer be approached as a benign lesion?: a population-level analysis of survival among 1,200 patients.

BACKGROUND

Minimally invasive follicular thyroid cancer (MIFC) is an encapsulated follicular tumor of low malignant potential. To date, histological criteria are still under debate, and there are no population-level data regarding characteristics and outcomes of patients with MIFC.

METHODS

Patients diagnosed with MIFC in the Surveillance, Epidemiology, and End Results (SEER) database from 2000 to 2009 were included. Summary statistics were utilized to analyze patient characteristics; Kaplan-Meier analysis, and one-sample log-rank test were performed.

RESULTS

A total of 1,200 patients with MIFC and 4,208 with widely invasive follicular thyroid cancer (WIFC) were identified over 10 years of follow-up. MIFC was more common than WIFC in younger patients (mean age 49 vs. 52.3 years; p 0.001). More patients with MIFC were alive at the end of follow-up (96.8 vs. 86.5% WIFC; p 0.001). Patients diagnosed with MIFC were less likely than those with WIFC to have lymph nodes involved and distant metastases (0.9 vs. 3.6% and 0.5 vs. 8.9%, respectively; both p 0.001). Only 2 of 1,200 patients died of disease-specific causes; overall survival was comparable to the general US population (p = 0.16). Total thyroidectomy and RAI ablation were not associated with improvement in patient outcomes (p = 0.2 and 0.443, respectively).

CONCLUSIONS

MIFC is associated with survival comparable to that of the normative US general population. Thyroid lobectomy alone may be considered adequate treatment in these patients.