Table 3. Final multivariate model of overall survival for entire cohort, elderly cohort and young patient cohort.

Variables	Hazard ratio (95% CI)	P-value
(A) Entire cohort
Age, ⩾70 years	1.35 (1.07–1.70)	0.01
Tumour size, >20 mm	1.43 (1.10–1.85)	0.007
Margins, involved	1.69 (1.35–2.12)	<0.0001
Perineural invasion, positive	1.33 (1.02–1.72)	0.033
Vascular invasion, positive	1.37 (1.09–1.71)	0.007
Adjuvant chemotherapy, none	1.38 (1.21–1.50)	<0.0001
(B) Older cohort (age ⩾70 years)
Tumour location, head	1.37 (1.03–1.59)	0.037
Margins, involved	1.98 (1.40–2.79)	<0.0001
Vascular invasion, positive	2.79 (1.60–3.24)	<0.0001
Adjuvant chemotherapy, none	1.47 (1.21–1.64)	0.002
(C) Young cohort (age <70 years)
Margins, involved	1.81 (1.36–2.42)	<0.0001
Adjuvant chemotherapy, none	1.35 (1.02–1.79)	0.035

Abbreviation: CI=confidence interval.