Table 2 Comparison of baseline characteristics of ESCC patients based on OPS in training set

Age (years, ≤60/> 60)

54(63.5)/31(36.5)

74(59.7)/50(40.3)

25(48.1)/27(51.9)

11(73.3)/4(26.7)

0.205

Gender (male/female)

58(68.2)/27(31.8)

81(65.3)/43(34.7)

39(75.0)/13(25.0)

10(66.7)/5(33.3)

0.660

Tumor length (cm, ≤3.0/> 3.0)

34(40.0)/51(60.0)

40(32.3)/84(67.7)

9(17.3)/43(82.7)

1(6.7)/14(93.3)

0.007

Tumor location (upper/middle/lower)

4(4.7)/36(42.4)/45(52.9)

8(6.5)/57(46.0)/59(47.5)

4(7.7)/22(42.3)/26(50.0)

1(6.7)/7(46.7)/7(46.7)

0.984

Vessel invasion (no/yes)

77(90.6)/8(9.4)

103(83.1)/21(16.9)

43(82.7)/9(17.3)

8(53.3)/7(46.7)

0.004

Perineural invasion (no/yes)

76(89.4)/9(10.6)

94(75.8)/30(24.2)

39(75.0)/13(25.0)

10(66.7)/5(33.3)

0.041

Differentiation (well/moderate/poor)

15(17.6)/61(71.8)/9(10.6)

15(12.1)/81(65.3)/28(22.6)

9(17.3)/36(69.2)/7(13.5)

2(13.3)/6(40.0)/7(46.7)

0.025

TNM stage (I/II/III)

25(29.4)/39(45.9)/21(24.7)

45(36.3)/34(27.4)/45(36.3)

8(15.4)/17(32.7)/27(51.9)

1(6.7)/4(26.7)/10(66.7)

< 0.001

Adjuvant treatment (no/yes)

65(76.5)/20(23.5)

84(67.7)/40(32.3)

38(73.1)/14(26.9)

11(73.3)/4(26.7)

0.576

GPS (0/1/2)

85(100)/0(0)/0(0)

97(78.2)/27(21.8)/0(0)

0(0)/42(80.8)/10(19.2)

0(0)/0(0)/15(100)

< 0.001

SIS (0/1/2)

52(61.2)/28(32.9)/5(5.9)

74(59.7)/41(33.1)/9(7.2)

14(26.9)/35(67.3)/3(5.8)

0(0)/14(93.3)/1(6.7)

< 0.001

PNI (≤47.5/> 47.5)

13(15.3)/72(84.7)

58(46.8)/66(53.2)

37(71.2)/15(28.8)

15(100)/0(0)

< 0.001

SII (≤558/> 558)

45(52.9)/40(47.1)

50(40.3)/74(59.7)

22(42.3)/30(57.7)

1(6.7)/14(93.3)

0.008