Table 6. Univariate analysis of factors for survival in upper, middle, and lower thoracic ESCC.

Factor	Upper				Middle/lower
	HR	95% CI	P value		HR	95% CI	P value
Sex (M/F)	0.622	0.290–1.334	0.223		1.205	0.632–2.297	0.572
Age (≤60/>60)	0.600	0.248–1.449	0.256		1.448	0.781–2.685	0.240
Vascular invasion (P/N)	2.800	1.658–6.772	0.022		1.697	0.894–3.219	0.106
Nerve invasion (P/N)	2.078	0.609–7.089	0.243		1.611	0.901–2.881	0.107
Differentiation (H-HM/M-ML)	0.725	0.314–1.675	0.452		0.540	0.307–0.950	0.033
Tumor size (<5/≥5 cm)	1.966	0.909–4.253	0.086		2.108	1.170–3.799	0.013
T stage (T1–2/T3–4)	2.646	1.130–6.195	0.025		2.728	1.518–4.900	0.001
TNM stage (I–II/III–IV)	3.060	1.255–7.465	0.014		4.046	2.121–7.718	<0.001
Total lymph nodes (P/N)	2.035	0.915–4.527	0.081		2.510	1.398–4.507	0.002
Supraclavicular lymph nodes (P/N)	2.055	0.926–4.562	0.077		3.150	1.659–5.982	<0.001

ESCC, esophageal squamous cancer; M, male; F, female; H, high differentiation; M, medium differentiation; L, low differentiation; P, positive; N, negative.