Timing of adjuvant radioactive iodine therapy does not affect overall survival in low- and intermediate-risk papillary thyroid carcinoma

Abstract

There is no consensus regarding the timing of adjuvant radioactive iodine therapy (RAI) therapy in low- and intermediate-risk papillary thyroid carcinoma (PTC). We analyzed the impact of adjuvant RAI on overall survival (OS) in low- and intermediate-risk PTC. The National Cancer Data Base was queried from 2004 to 2011 for pN0M0 PTC patients having near/subtotal or total thyroidectomy and adjuvant RAI. Tumors ≤1 cm with negative margins were low risk while 1.1- to 4-cm tumors with negative margins or ≤1 cm with microscopic margins were termed intermediate risk. RAI in ≤3 months and between 3 and 12 months was termed as early and delayed, respectively. Survival analysis was performed after adjusting for patient and tumor-related variables. There were 7,306 low-risk and 16,609 intermediate-risk patients. Seventeen per cent lowrisk and 15 per cent intermediate-risk patients had delayed RAI. Kaplan-Meier analysis did not show a difference in OS for early versus delayed RAI administration in low- (10-year OS 94.5% vs 94%, P 5 0.627) or intermediate-risk (10-year OS 95.3% vs 95.9%, P 5 0.944) patients. In adjusted survival analysis, RAI timing did not affect OS in all patients (hazard ratios 5 0.98, 95% confidence interval 5 0.71-1.34, P 5 0.887). In conclusion, the timing of postthyroidectomy adjuvant RAI therapy does not affect OS in low- or intermediate-risk PTC.