Table 1.

Continuous variables binned into subgroups

Variable	Bins created
Age at diagnosis	<69, ≥69
Year of diagnosis	1988–1997, 1998–2003, ≥2004
Tumor size (in mm)	0–19, 20–36, ≥37 mm
Regional lymph nodes examined	‘Few’ (SEER ≤5, SI ≤9), ‘Moderate’ (SEER 6–12, SI 10–16), ‘Large’ (SEER ≥13, SI ≥17)
Regional lymph nodes positive	0, 1, 2, ≥3
Lymph node ratio	0, <0.2, 0.2–0.3, ≥0.3

SEER surveillance, epidemiology, and end results, SI single institution