Table 3.

Multivariate Cox Regression Analysis of Overall Survival

Variables	Adjusted Hazard Ratioa	95% Confidence Interval	P
Age (per year)	1.024	1.008–1.039	.003
Histology
Squamous cell	Reference
Adenoid cystic	0.443	0.273–0.719	.001
Other	0.626	0.356–1.104	.68
Surgery type
Simple resection	Reference
Total/radical surgery	1.073	0.668–1.723	.77
Debulking	2.566	1.402–4.696	.002
Margin status
Negative	Reference
Positive	1.784	1.105–2.883	.018
Unknown	1.790	0.902–3.552	.095

^aModel adjusted for Charlson-comorbidity score, tumor size, lymph node status, and receipt of adjuvant therapy.