Table 14.

Characteristics According to the American Thyroid Association Risk Stratification System and AJCC/TNM Staging System That May Impact Postoperative Radioiodine Decision-Making

ATA risk Staging (TNM)	Description	Body of evidence suggests RAI improves disease-specific survival?	Body of evidence suggests RAI improves disease-free survival?	Postsurgical RAI indicated?
ATA low risk  T1a  N0,Nx  M0,Mx	Tumor size ≤1 cm (uni-or multifocal)	No	No	No
ATA low risk  T1b,T2  N0, Nx  M0,Mx	Tumor size >1–4 cm	No	Conflicting observational data	Not routineb—May be considered for patients with aggressive histology or vascular invasion (ATA intermediate risk).
ATA low to intermediate risk  T3  N0,Nx  M0,Mx	Tumor size >4 cm	Conflicting data	Conflicting observational data	Considerb—Need to consider presence of other adverse features. Advancing age may favor RAI use in some cases, but specific age and tumor size cutoffs subject to some uncertainty.a
ATA low to intermediate risk  T3  N0,Nx  M0,Mx	Microscopic ETE, any tumor size	No	Conflicting observational data	Considerb—Generally favored based on risk of recurrent disease. Smaller tumors with microscopic ETE may not require RAI.
ATA low to intermediate risk  T1-3  N1a  M0,Mx	Central compartment neck lymph node metastases	No, except possibly in subgroup of patients ≥45 years of age (NTCTCSG Stage III)	Conflicting observational data	Considerb—Generally favored, due to somewhat higher risk of persistent or recurrent disease, especially with increasing number of large (>2–3 cm) or clinically evident lymph nodes or presence of extranodal extension. Advancing age may also favor RAI use.a However, there is insufficient data to mandate RAI use in patients with few (<5) microscopic nodal metastases in central compartment in absence of other adverse features.
ATA low to intermediate risk  T1-3  N1b  M0,Mx	Lateral neck or mediastinal lymph node metastases	No, except possibly in subgroup of patients ≥45 years of age	Conflicting observational data	Considerb—Generally favored, due to higher risk of persistent or recurrent disease, especially with increasing number of macroscopic or clinically evident lymph nodes or presence of extranodal extension. Advancing age may also favor RAI use.a
ATA high risk  T4  Any N  Any M	Any size, gross ETE	Yes, observational data	Yes, observational data	Yes
ATA high risk  M1  Any T  Any N	Distant metastases	Yes, observational data	Yes, observational data	Yes

^aRecent data from the NTCTCSG (National Thyroid Cancer Treatment Cooperative Study Group) have suggested that a more appropriate prognostic age cutoff for their and other classification systems could be 55 years, rather than 45 years, particularly for women.

^bIn addition to standard clinicopathologic features, local factors such as the quality of preoperative and postoperative US evaluations, availability and quality of Tg measurements, experience of the operating surgeon, and clinical concerns of the local disease management team may also be considerations in postoperative RAI decision-making.