Table 1 Association of baseline characteristics with ICTOS in both training and validation sets

Age

0.06

0.49

0.49

 < 42 years

45 (32.6)

52 (44.8)

81 (46.3)

38 (52.1)

 ≥ 42 years

93 (67.4)

64 (55.2)

94 (53.7)

35 (47.9)

Sex

0.02

0.40

 Male

109 (79.0)

75 (64.7)

144 (82.3)

56 (76.7)

 Female

29 (21.0)

41 (35.3)

31 (17.7)

17 (23.3)

Staging^a

0.04

0.80

 III

84 (70.9)

55 (47.4)

95 (65.7)

46 (73.0)

 IV

54 (39.1)

61 (52.6)

60 (34.3)

27 (37.0)

T stage^a

0.21

0.33

 T1

4 (2.9)

2 (1.7)

5 (2.9)

1 (1.4)

 T2

14 (10.1)

7 (6.0)

8 (4.6)

5 (6.8)

 T3

82 (59.4)

62 (53.4)

114 (65.1)

40 (54.8)

 T4

38 (27.5)

45 (38.8)

48 (27.4)

27 (37.0)

N stage^a

0.48

0.08

0.08

 N1

66 (47.8)

47 (40.5)

98 (56.0)

36 (49.3)

 N2

50 (36.2)

46 (39.7)

62 (35.4)

35 (47.9)

 N3

22 (15.9)

23 (19.8)

15 (8.6)

2 (2.7)

Cervical nodal necrosis

0.90

0.32

 No

99 (71.7)

85 (73.3)

114 (65.1)

53 (72.6)

 Yes

39 (28.3)

31 (26.7)

61 (34.9)

20 (27.4)

Primary tumor volume

< 0.001

< 0.001

0.56

0.56

 < 34 ml

97 (70.3)

53 (45.7)

88 (50.3)

33 (45.2)

 ≥ 34 ml

41 (29.7)

63 (54.3)

87 (49.7)

40 (54.8)

Pretreatment pEBV DNA level

0.17

0.08

 < 2000 copy/ml

75 (54.3)

52 (44.8)

60 (45.7)

24 (32.9)

 ≥ 2000 copy/ml

63 (45.7)

64 (55.2)

95 (54.3)

49 (67.1)

Chemoradiotherapy regimen

0.22

0.64

 ICT+CCRT

62 (44.9)

62 (53.4)

86 (49.1)

39 (53.4)

 CCRT

76 (55.1)

54 (46.6)

89 (50.9)

34 (46.6)