Table 1.

Comparison of baseline data of patients between the two sets

	Training set (n=230)	Validation set (n=98)	χ2	P
Age (years)
≥65	133	51	0.934	0.334
<65	97	47
Sex
Male	53	24	0.080	0.777
Female	177	74
BMI (kg/m2)
≥23	179	80	0.599	0.439
<23	51	18
Operation mode
Open surgery	80	37	0.265	0.607
Laparoscopic surgery	150	61
Pathological type
Adenocarcinoma	207	85	0.75	0.387
Squamous carcinoma	23	13
Tumor size
≥3 cm	127	57	0.242	0.623
<3 cm	103	41
T-staging
T1b	41	17	0.833	0.659
T2	115	54
T3	74	27
Lymph node metastasis
With	92	43	0.427	0.514
Without	138	55
Perineural invasion
With	97	44	0.208	0.648
Without	133	54
Vascular invasion
With	78	29	0.584	0.445
Without	152	69
Differentiation degree
Poorly differentiated	78	37	0.446	0.504
Moderately or well differentiated	152	61

Note: BMI, body mass index.