Table 4.

Tumor Characteristics and Estimated Probability of Nodal Metastasis with Observed Rate of Nodal Metastasis

Tumor Characteristics	Model Estimated Probability of Nodal Metastasis	Observed Rate of Nodal Metastasis
T1a with no other risk factors	Very low (<5%)	2/57 (3.5%)
T1a with 1 or more risk factors*	Estimated >5%*	1/15 (6.7%)*
T1b with no other risk factors	Low (5-10%)	2/27 (7.4%)
T1b with ALI OR >2cm alone	Intermediate (15-20%)	6/38 (15.8%)
T1b with high grade alone	High (~20%)	3/13 (23.1%)
T1b with 2 or more additional risk factors**	High (30-60%)	27/60 (45.0%)

^*Most tumors in this category had a single risk factor (tumor size > 2 cm, N=10; high grade, N=3) and would have a low (5-10%) estimated probability. T1a cancers with two risk factors were rare (N=2); estimated probability in this group was intermediate (15-20%), which could not be confirmed due to the rarity of these cases.

^**These tumors invaded the submucosa and had at least 2 additional risk factors (ALI, high tumor grade and/or tumor size > 2cm)