17
Table 6. Characteristics According to the ATA Risk
Stratification System and AJCC/TNM Staging
System That May Affect Post-operative RAI
Decision-Making
ATA recurrence risk
Body of Evidence
Suggests
RAI Improves
Disease- Specific
Survival?
Body of
Evidence
Suggests
RAI Improves
Disease-Free
Survival?
Post-Surgical RAI
Indicated?
Staging
T N M Description
ATA low risk No No No
T1a
N0, Nx
M0, Mx
Tumor size
≤1 cm (uni- or
multi- focal)
ATA low risk No Conflicting
observational
data
Not routine
a
– may
be considered
for patients with
aggressive histolog y
or vascular invasion
(ATA intermediate
risk)
T1b, T2
N0, Nx
M0, Mx
Tumor size
>1–4 cm
ATA low to intermediate risk Conflicting data Conflicting
observational
data
Consider
a
– need to
consider presence of
other adverse features.
Advancing age may
favor RAI use in some
cases, but specific age
and tumor size cut-
offs subject to some
uncertainty*
T3
N0, Nx
M0, Mx
Tumor size
>4 cm
ATA low to intermediate risk No Conflicting
observational
data
Consider
a
– generally
favored based on risk
of recurrent disease.
Smaller tumors with
microscopic ETE may
not require RAI
T3
N0, Nx
M0, Mx
Microscopic
extra- thyroidal
extension, any
tumor size
