Comparable outcomes for patients with pT1a and pT1b differentiated thyroid cancer: Is there a need for change in the AJCC classification system?

Overview

INTRODUCTION: The current American Joint Committee on Cancer TNM classification for differentiated thyroid cancer (DTC) separates T1 status into T1a and T1b based on a 1-cm cutoff for maximal tumor dimension. In 2009, the American Thyroid Association recommended total thyroidectomy for tumors >1 cm in contrast to the possibility of lobectomy for tumors ≤ 1 cm. Our aim was to investigate the prognostic significance of a 1-cm tumor cutoff. METHODS: From an institutional database of 3,664 patients with DTC, 1,522 patients with T1 tumors without neck disease or distant metastases were identified. Patient, tumor, and treatment characteristics were compared. Disease-specific survival (DSS) and recurrence-free survival (RFS) outcomes were analyzed. RESULTS: Total thyroidectomy rates were similar between patients with T1a and T1b tumors (P = .307). With a median follow-up of 46 months (range, 1-320), there were no disease-specific deaths in the T1a or T1b groups. In total, 18 patients (1.2%) experienced a recurrence. Five-year RFS was comparable for patients with T1a and T1b tumors (98.6 vs 98.6%; P = .224). CONCLUSION: T1a and T1b tumors have similar prognosis both in terms of DSS and RFS. It seems that a distinction between tumors of <1 and >1 cm is of no prognostic benefit.