Table 2. Multivariable Analysis of Positive Surgical Margin Association.

Characteristic	Effect Index (95% CI)	p-value
Age, yr, mean (SD)	1.00 (0.99–1.00)	0.581
Race
Non-Hispanic White	[Reference]	NA
Black	1.18 (0.98–1.41)	0.076
Hispanic	1.08 (0.86–1.37)	0.488
Asian-Pacific Islander	0.93 (0.70–1.21)	0.588
Other-unknown	0.97 (0.67–1.37)	0.848
Insurance
Private	[Reference]	NA
Uninsured	1.08 (0.84–1.38)	0.521
Medicare-Medicaid or other government	1.23 (1.08–1.41)	0.002
Unknown	1.17 (0.71–1.85)	0.521
Year of diagnosis	0.98 (0.95–1.00)	0.11
Subsite
Oral tongue	[Reference]	NA
Lip	1.02 (0.63–1.57)	0.939
Gum-alveolar ridge	1.14 (0.96–1.36)	0.145
Floor of mouth	1.10 (0.93–1.30)	0.287
Hard palate	1.98 (1.52–2.56)	<0.001
Other *	1.28 (1.09–1.51)	0.003
Clinical T category
cT3	[Reference]	NA
cT4	1.39 (1.21–1.60)	<0.001
Clinical N category
cN0	[Reference]	NA
cN1	1.20 (1.03–1.40)	0.021
cN2	1.28 (1.13–1.45)	<0.001
cN3	1.58 (0.98–2.48)	0.05
Lymphovascular invasion
Negative	[Reference]	NA
Positive	1.60 (1.42–1.80)	<0.001
Histologic grade
Well differentiated	[Reference]	NA
Moderately differentiated	1.69 (1.41–2.04)	<0.001
Poorly differentiated-Undifferentiated	2.00 (1.63–2.48)	<0.001
Distance to treatment center
<=50 miles	[Reference]	NA
>50 miles	0.94 (0.82–1.06)	0.319
Academic center
No	[Reference]	NA
Yes	0.86 (0.76–0.98)	0.022
Treatment center volume
Low (<=20 cases/yr)	[Reference]	NA
High (>=20 cases/yr)	0.73 (0.67–0.79)	<0.001

^*The “other” category for “subsite” includes hard palate, retromolar trigone, and mouth (overlapping or no otherwise specified)