Table 3. Relationship of individual variables to death (Cox proportional hazards method).

Variable	P value	Hazard ratio (HR)	95% confidence limit
Histology
Squamous cell carcinoma	–	Reference	Reference
Adenocarcinoma	0.264	1.608	0.698–3.703
Large cell carcinoma	0.0036	4.323	1.611–11.598
Lung resection
Segment resection	–	Reference	Reference
Lobectomy	0.117	0.461	0.174–1.216
Pneumonectomy	0.046	0.252	0.065–0.976
Lymph node metastases
Single	–	Reference	Reference
Multiple	0.2816	1.503	0.715–3.155
Tumor location
Central tumor <2 cm	–	Reference	Reference
Peripheral tumor	0.360	1.416	0.672–2.981
UICC
IIA	–	Reference	Reference
IIB	0.0417	2.197	1.030–4.686

UICC, Union for International Cancer Control.