Table 1. Clinical characteristics of patients with and without lymph node metastasis in the training and validation cohorts.

Variable	Training cohort (n=233)			Validation cohort (n=101)
	LN−	LN+		LN−	LN+
Gender
Male	80	83		31	43
Female	31	39		10	17
Age (years)
Range	49–78	40–82		48–79	56–77
Mean ± standard deviation	65.58±6.58	64.07±8.01		66.52±7.94	66.93±5.70
Location of the tumor
Upper thoracic esophagus	15	19		5	7
Middle thoracic esophagus	79	79		30	38
Lower thoracic esophagus	17	24		6	15
Lymph node status	111	122		41	60
Lymph node metastasis
RLNM	–	69		–	34
NRLNM	–	53		–	26

LN, lymph node; +, metastasis positive; −, metastasis negative; RLNM, regional lymph node metastasis; NRLNM, non-regional lymph node metastasis.