Basic Characteristics
A total of 167 patients participated in the study. Among them, 134 patients (Approximate 70%) were randomly assigned to the training group to build a nomogram, and the remaining 33 patients (Approximate 30%) were assigned to the verification group. Table 1 shows the data of the clinicopathological characteristics of the 167 patients. The three-year and five-year survival rates were 0.934 and 0.844, respectively. We found that 141 patients (84.4%) achieved a five-year survival time in all patients. These clinicopathological factors did not differ significantly between the training and validation cohorts.
Table 1
Patient, tumor, and treatment-related characteristics of thymic tumor (n = 167)
Characteristic
|
Training Cohort(n = 134)
|
|
Validation Cohort(n = 33)
|
|
|
N
|
%
|
N
|
%
|
Gender
Male
Female
|
71
63
|
53.0
47.0
|
20
13
|
60.6
39.4
|
Age(years)
≤ 60
>60
|
104
30
|
77.6
22.4
|
28
5
|
84.8
15.2
|
Smoking history
Never
Ever
|
102
32
|
76.1
23.9
|
24
9
|
72.7
27.3
|
Drinking history
No
Yes
|
116
18
|
86.6
13.4
|
30
3
|
90.0
9.1
|
Family history of tumor
No
Yes
|
112
22
|
83.6
16.4
|
29
4
|
87.9
12.1
|
Underlying diseases
No
Yes
|
103
31
|
76.9
23.1
|
23
10
|
69.7
30.3
|
Tumor size
≤ 6
>6
|
77
57
|
57.5
42.5
|
15
18
|
45.5
54.5
|
pT stage
T1
T2-3
T4
|
100
25
9
|
74.6
18.7
6.7
|
22
9
2
|
66.7
27.3
6.1
|
M stage
M0
M1
|
127
7
|
94.8
5.2
|
30
3
|
90.9
9.1
|
Masaoka stage
I
II-III
IV
|
63
64
7
|
47.0
47.8
5.2
|
13
17
3
|
39.4
51.5
9.1
|
WHO stage
A-AB
B1-B3
C
|
52
71
11
|
38.8
53.0
8.2
|
11
14
8
|
33.3
42.4
24.2
|
Myasthenia gravis,
No
Yes
|
123
11
|
91.8
8.2
|
31
2
|
93.9
6.1
|
BMI
≤ 18.8
>18.8
|
13
121
|
9.7
90.3
|
4
29
|
12.1
87.9
|
tumor capsule status
Incomplete
Complete
|
47
87
|
64.9
35.1
|
11
22
|
66.7
33.3
|
Invasion of great vessels
No
Yes
|
102
32
|
76.1
23.9
|
25
8
|
75.8
24.2
|
ALB
≤ 42.6
>42.6
|
49
85
|
36.6
63.4
|
14
19
|
42.4
57.6
|
GLB
≤ 23.2
>23.2
|
15
119
|
11.2
88.8
|
7
26
|
21.2
78.8
|
A/G
≤ 1.3
>1.3
|
28
106
|
20.9
79.1
|
4
29
|
12.1
87.9
|
Hb
≤ 124
>124
|
32
102
|
23.9
76.1
|
6
27
|
18.2
81.8
|
NE
≤ 5.6
>5.6
|
116
18
|
86.6
13.4
|
28
5
|
84.8
15.2
|
LY
≤ 1.5
>1.5
|
26
108
|
19.4
80.6
|
7
26
|
21.2
78.8
|
NE/LY(NLR)
≤ 3.1
>3.1
|
119
15
|
88.8
11.2
|
29
4
|
87.9
12.1
|
PLT
≤ 314
>314
|
121
13
|
90.3
9.7
|
29
4
|
87.9
12.1
|
PLT/LY(PLR)
≤ 145.7
>145.7
|
105
29
|
78.4
21.6
|
28
5
|
84.8
15.2
|
PLT/NE*LY(SII)
≤ 688.5
>688.5
|
116
18
|
86.6
13.4
|
24
9
|
72.7
27.3
|
NLR: neutrophil-to-lymphocyte ratio; Hb: hemoglobin; ALB: albumin; BMI: body mass index; NE: neutrophil count; LY: lymphocyte count; GLB: Globulin; SII: systemic immune-inflammation Index; PLT: platelet; PLR: platelet-lymphocyte ratio; pT stage: Pathological T stage. |
Univariable and Multivariable Analyses in the Training Cohort
According to the results of univariate Cox regression analysis, there were nine variables related to OS: underlying disease, BMI, T stage, histology, ALB, Neutrophils(NE), NLR, systemic immune-inflammation Index (SII), and Globulin (GLB) (Table 2). In the multivariate Cox regression analysis, four parameters were defined as independent prognostic factors of OS: T stage (T1 vs. T2-3, hazard ratio, HR = 6.138, 95% confidence interval, CI [1.557–24.189], T1 vs. T4, HR = 6.892, 95% CI [1.752–27.109]), ALB (HR = 0.172, 95% CI [0.044–0.676]), underlying disease (HR = 12.584, 95% CI [3.067–51.634]), and NLR (HR = 13.215, 95% CI [3.074–56.817]) (Table 2).
Table 2
Univariate and multivariate analysis results in Training cohort(n = 134)
Variable
|
Univariate
analysis
|
Multivariate analysis
|
|
|
|
P
|
HR
|
95%CI
|
P
|
Gender
Male vs Female
|
.275
|
|
|
|
Age(years)
≤ 60 vs ༞60
|
.694
|
|
|
|
Smoking history
Never vs Ever
|
.394
|
|
|
|
Drinking history
No vs Yes
|
.133
|
|
|
|
Family history of tumor
No vs Yes
|
.272
|
|
|
|
Underlying diseases
No vs Yes
|
.018
|
Reference
12.584
|
3.067–51.634
|
.000
|
Tumor size
≤ 6 vs ༞6
|
.380
|
|
|
|
pT stage
T1 vs T2-3
T1 vs T4
|
.001
|
Reference
6.138
6.892
|
1.557–24.189
1.752–27.109
|
.010
.006
|
M stage
M0 vs M1
|
.795
|
|
|
|
Masaoka stage
I vs II-III
I vs IV
|
.112
|
|
|
|
WHO stage
A-AB vs B1-B3
A-AB vs C
|
.021
|
|
|
|
Myasthenia gravis,
No vs Yes
|
.476
|
|
|
|
BMI
≤ 18.8 vs ༞18.8
|
.015
|
|
|
|
tumor capsule status
Incomplete vs Complete
|
.118
|
|
|
|
Invasion of great vessels
No vs Yes
|
.406
|
|
|
|
ALB
≤ 42.6 vs ༞42.6
|
.004
|
Reference
.172
|
.044-.676
|
.012
|
GLB
≤ 23.2 vs ༞23.2
|
.009
|
|
|
|
A/G
≤ 1.3 vs ༞1.3
|
.193
|
|
|
|
Hb
≤ 124 vs ༞124
|
.344
|
|
|
|
NE
≤ 5.6 vs ༞5.6
|
.000
|
|
|
|
LY
≤ 1.5 vs ༞1.5
|
.154
|
|
|
|
NE/LY(NLR)
≤ 3.1 vs ༞3.1
|
.000
|
Reference
13.215
|
3.074–56.817
|
.001
|
PLT
≤ 314 vs ༞314
|
.733
|
|
|
|
PLT/LY(PLR)
≤ 145.7 vs ༞145.7
|
.065
|
|
|
|
PLT/NE*LY(SII)
≤ 688.5 vs ༞688.5
|
.002
|
|
|
|
NLR: neutrophil-to-lymphocyte ratio; Hb: hemoglobin; ALB: albumin; BMI: body mass index; NE: neutrophil count; LY: lymphocyte count; GLB: Globulin; SII: systemic immune-inflammation Index; PLT: platelet; PLR: platelet-lymphocyte ratio; pT stage: Pathological T stage. |
Establishment of the Nomogram
According to the results of the multivariate Cox regression analysis, T stage, ALB, underlying disease, and NLR were defined as independent prognostic factors, and these factors were integrated to form a nomogram (Fig. 2). In the training cohort, the C index was 0.886 (95% CI: 0.804–0.968), which was higher than that of the T staging prediction model (C index: 0.725, 95% CI: 0.602–0.848). Internal calibration curves for the three- and five-year OS closely matched those of the baseline in the training cohort (Fig. 3Aand B).
Verification of the Nomogram
To better verify the actual predictive power of the nomogram, the above results were verified using the verification group data, showing that the C index was 0.741 (95% CI: 0.592–0.890), and the five-year and three-year external calibration curves met those of the standard baseline (Fig. 3C and D). We also used the ROC curve to verify the nomogram performance (Fig. 4). The AUC values of the training and validation groups at three and five years were both greater than 0.7 and by comparing the AUC values of the two groups, the nomogram model were significantly better than those of the T staging, showing better accuracy of the nomogram in predicting OS.
Decision Curve Analysis
Decision Curve Analysis (DCA) is a novel method for evaluating prognostic strategies that can evaluate the predictive power of prognostic models. Figure 5 shows the nomogram and DCA curve of T staging in the training and validation cohorts. Compared with the T staging, the DCA of the nomogram has a higher net benefit, which indicates that the nomogram has a better net benefit. The clinical utility of the nomogram was better than that of the T staging.
Risk Stratification of OS
Based on the nomogram scores, patients were divided into low-risk (0–73 points), medium-risk (74–169 points), and high-risk (170 points or higher) subgroups. In the training cohort, there were 82 patients in the low-risk group, 43 patients in the intermediate-risk group, and 9 patients in the high-risk group. In the validation cohort, 16 patients were included in the low-risk group, 8 patients were included in the medium-risk group, and 9 patients were included in the high-risk group. There were significant differences in the incidence of OS among the subgroups, and the survival rate of the high-risk subgroup was lower than that of the other groups (P < 0.05) (Fig. 6).