Table 4. Multivariate Cox regression analysis of prognostic factors in matched population.

Variables		CSS			OS
	HR	95%CI	P	HR	95%CI	P
Age
<62
≥62				2.805	1.957–4.019	<0.001***
Tumor extent
Adjacent connective tissue	1		1
Adjacent organs or structures	3.957	1.840–8.507	<0.001***	2.326	1.569–3.446	<0.001***
PORT
Yes/ No	3.077	1.585–5.974	0.001***	1.692	1.171–2.445	0.005**

Abbreviations: HR, hazard ratio; CI, confidence interval; CSS, cancer-specific survival; OS, overall survival; PORT, postoperative radiotherapy.