Table 1.

Demographics and clinicopathological variables of the training, internal validation, and external validation set.

Characteristics	Training cohort (n = 696)		Internal validation cohort (n = 298)		External validation cohort (n = 133)
	N	%	N	%	N	%
Age (years)
<65	353	50.7	159	53.4	110	82.7
⩾65	343	49.3	139	46.6	23	17.3
Sex
Male	421	60.5	182	61.1	66	49.6
Female	275	39.5	116	38.9	67	50.4
Race
White	450	64.7	192	64.4	-	-
Other	246	35.3	106	35.6	-	-
Grade
Well/moderately differentiated	149	21.4	67	22.5	19	14.3
Poorly differentiated	547	78.6	231	77.5	114	85.7
T stage
1 + 2	47	6.8	22	7.4	11	8.3
3 + 4	649	93.2	276	92.6	122	91.7
N stage
0 + 1	342	49.1	138	46.3	46	34.6
2 + 3	354	50.9	160	53.7	87	65.4
Tumor site
Proximal third	129	18.5	46	15.4	22	16.5
Mid third	170	24.4	77	25.8	39	29.3
Distal third	259	37.2	110	37	42	31.6
Greater curvature	48	7	16	5.4	22	16.5
Overlapping	90	12.9	49	16.4	8	6
Metastatic sites
Distant lymph node(s) only	105	15.1	40	13.4	17	12.8
Organ	538	77.3	230	77.2	94	70.7
Overlapping	53	7.6	28	9.4	22	16.5
Chemotherapy
With	375	53.9	161	54	122	91.7
Without	321	46.1	137	46	11	8.3
Tumor size (cm)
⩽60	364	52.3	163	54.7	67	50.4
>60	332	47.7	135	45.3	66	49.6