Comparison of clinicopathological characteristics between the training cohort and the validation cohort
Based on the inclusion criteria, we identified a total of 2,610 patients who had well-documented patient data for analysis. According to the ratio of 2:1, 1,740 were included in the training cohort and 870 were included in the validation cohort. The clinical and pathological data of the patients between the two groups did not differ significantly (p > 0.05). (Table 1).
Table 1 Comparison of the descriptive characteristics between the training cohort and the validation cohort
Characteristics
|
|
Training
|
%
|
Validation
|
%
|
P -value
|
Age at diagnosis (years)
|
N
|
1740
|
66.7
|
870
|
33.3
|
0.895
|
|
|
67.57±11.70
|
|
67.64±12.03
10.210.10.2210.4
|
|
|
Age(years)
|
|
|
|
|
|
0.542
|
|
≦ 50
|
137
|
7.9
|
79
|
9.1
|
|
|
51-60
|
336
|
19.3
|
147
|
16.9
|
|
|
61-70
|
539
|
31.0
|
269
|
30.9
|
|
|
71-80
|
456
|
26.2
|
233
|
26.8
|
|
|
>80
|
272
|
15.6
|
142
|
16.3
|
|
Tumor location1
|
|
|
|
|
|
0.716
|
|
Central
|
744
|
42.8
|
403
|
46.3
|
|
|
UIQ
|
82
|
4.7
|
35
|
4.0
|
|
|
LIQ
|
32
|
1.8
|
14
|
1.6
|
|
|
UOQ
|
222
|
12.8
|
100
|
11.5
|
|
|
LOQ
|
65
|
3.7
|
35
|
4.0
|
|
|
Nipple
|
79
|
4.5
|
39
|
4.5
|
|
|
Others
|
228
|
13.1
|
100
|
11.5
|
|
|
Overlapping
|
288
|
16.6
|
144
|
16.6
|
|
Tumor stage
|
|
|
|
|
|
0.808
|
|
T1
|
866
|
49.8
|
421
|
48.4
|
|
|
T2
|
704
|
40.5
|
360
|
41.4
|
|
|
T3
|
47
|
2.7
|
21
|
2.4
|
|
|
T4
|
123
|
7.1
|
68
|
7.8
|
|
Pathological type
|
|
|
|
|
|
0.334
|
|
IDC
|
1582
|
90.9
|
789
|
90.7
|
|
|
ILC
|
14
|
0.8
|
8
|
0.9
|
|
|
ADENO-CA
|
92
|
5.3
|
39
|
4.5
|
|
|
Paget
|
20
|
1.1
|
8
|
0.9
|
|
|
Others*
|
32
|
1.8
|
26
|
3.0
|
|
Histologic grade
|
|
|
|
|
|
0.613
|
|
Ⅰ
|
251
|
14.4
|
124
|
14.3
|
|
|
Ⅱ
|
936
|
53.8
|
453
|
52.1
|
|
|
Ⅲ
|
553
|
31.8
|
293
|
33.7
|
|
ER
|
|
|
|
|
|
0.620
|
|
Positive
|
1707
|
98.1
|
851
|
97.8
|
|
|
Negative
|
33
|
1.9
|
19
|
2.2
|
|
PR
|
|
|
|
|
|
0.724
|
|
Positive
|
1595
|
91.7
|
801
|
92.1
|
|
|
Negative
|
145
|
8.3
|
69
|
7.9
|
|
HER2 receptor status
|
|
|
|
|
|
0.899
|
|
Positive
|
215
|
12.4
|
106
|
12.2
|
|
|
Negative
|
1525
|
87.6
|
764
|
87.8
|
|
AJCC stage
|
|
|
|
|
|
0.930
|
|
Ⅰ
|
837
|
48.1
|
412
|
47.4
|
|
|
Ⅱ
|
626
|
36.0
|
319
|
36.7
|
|
|
Ⅲ
|
277
|
15.9
|
129
|
16.0
|
|
lymph node status
|
|
|
|
|
|
0.976
|
|
Negative
|
1179
|
67.8
|
590
|
67.8
|
|
|
Positive
|
561
|
32.2
|
280
|
32.2
|
|
Molecular subtype
|
|
|
|
|
|
0.730
|
|
Luminal A
|
1502
|
86.3
|
748
|
86.0
|
|
|
Luminal B
|
209
|
12
|
104
|
12.0
|
|
|
HER2+
|
6
|
0.3
|
2
|
0.2
|
|
|
TN
|
23
|
1.3
|
16
|
1.8
|
|
In cases of multifocal tumors or unifocal tumors that involved more than 1 quadrant, the tumor location was classified in the following order of priority: Central portion of breast(central), upper outer quadrant (UOQ), lower outer quadrant (LOQ), lower inner lower quadrant (LIQ), and upper inner quadrant (UIQ), nipple, Overlapping lesion of breast(Overlapping), Axillary tail of breast and Breast NOS(other). *others: metaplastic carcinoma, medullary carcinoma, Unspecified malignant neoplasms except for CNS, papillary carcinoma, infiltrating micropapillary carcinoma, tubular carcinoma, etc . (https://seer.cancer.gov/tools/solidtumor/Breast_STM.pdf)
|
Univariate logistic regression analysis of ALNM in the training cohort
Univariate logistic regression analysis was used to explore ALN metastasis-related variables (Table 2) and showed that age, tumor location, tumor stage, pathological type, histologic grade, ER, PR, Her-2, and molecular subtypes were related to MBC ALN metastasis (p < 0.05).
Table 2 Univariate analysis for factors associated with axillary lymph node metastasis
Variables
|
OR
|
OR 95% CI
|
P -value
|
Lower
|
Upper
|
|
Age
|
|
|
|
|
<0.001
|
|
≦ 50
|
1(REF)
|
|
|
|
|
51-60
|
0.896
|
0.601
|
1.337
|
0.592
|
|
61-70
|
0.572
|
0.390
|
0.838
|
0.004
|
|
71-80
|
0.452
|
0.304
|
0.670
|
<0.001
|
|
>80
|
0.335
|
0.215
|
0.522
|
<0.001
|
Tumor location
|
|
|
|
|
<0.001
|
|
Central
|
1(REF)
|
|
|
|
|
UIQ
|
0.380
|
0.216
|
0.668
|
0.001
|
|
LIQ
|
0.361
|
0.147
|
0.888
|
0.027
|
|
UOQ
|
0.528
|
0.377
|
0.740
|
<0.001
|
|
LOQ
|
0.600
|
0.3411
|
1.053
|
0.075
|
|
Nipple
|
0.859
|
0.530
|
1.395
|
0.540
|
|
Other
|
0.723
|
0.527
|
0.991
|
0.044
|
|
Overlapping
|
0.551
|
0.408
|
0.745
|
<0.001
|
Tumor stage
|
|
|
|
|
<0.001
|
|
T1
|
1(REF)
|
|
|
|
|
T2
|
6.065
|
4.703
|
7.823
|
<0.001
|
|
T3
|
24.513
|
12.099
|
49.667
|
<0.001
|
|
T4
|
53.929
|
30.248
|
96.150
|
<0.001
|
Pathological type
|
|
|
|
|
0.002
|
|
IDC
|
1(REF)
|
|
|
|
|
ILC
|
0.801
|
0.250
|
2.565
|
0.708
|
|
ADENO-CA
|
0.359
|
0.201
|
0.641
|
0.001
|
|
Paget
|
2.002
|
0.828
|
4.840
|
0.123
|
|
Other
|
0.462
|
0.189
|
1.129
|
0.090
|
Histologic grade
|
|
|
|
|
<0.001
|
|
I
|
1(REF)
|
|
|
|
|
II
|
3.065
|
1.977
|
4.752
|
<0.001
|
|
III
|
10.642
|
6.815
|
16.617
|
<0.001
|
|
|
|
|
|
|
ER
|
ER+
|
1(REF)
|
|
|
|
|
ER-
|
2.271
|
1.139
|
4.530
|
0.020
|
PR
|
PR+
|
1(REF)
|
|
|
|
|
PR-
|
1.541
|
1.089
|
2.181
|
0.015
|
HER2
|
HER2+
|
1(REF)
|
|
|
|
|
HER2-
|
0.544
|
0.407
|
0.727
|
<0.001
|
Molecular subtype
|
|
|
|
|
<0.001
|
|
LMA
|
1(REF)
|
|
|
|
|
LMB
|
1.809
|
1.348
|
2.429
|
<0.001
|
|
HER2
|
4.602
|
0.840
|
25.216
|
0.079
|
|
TN
|
1.770
|
0.771
|
4.066
|
0.178
|
Multivariate logistic regression analysis of ALNM in the training group
After adjusting the significant variables from the univariate analysis, the multivariate analysis found that age at diagnosis, tumor location, tumor stage, pathological type, and histologic grade stayed as independent predictive factors of ALNM. (Table 3)
Table 3 Multivariate logistic regression analysis for factors associated with ALNM
Variables
|
OR
|
OR 95% CI
|
P value
|
Lower
|
Upper
|
Age
|
|
|
|
|
<0.001
|
|
≦ 50
|
1(REF)
|
|
|
|
|
51-60
|
0.830
|
0.503
|
1.368
|
0.464
|
|
61-70
|
0.441
|
0.275
|
0.710
|
0.001
|
|
71-80
|
0.372
|
0.228
|
0.607
|
<0.001
|
|
>80
|
0.198
|
0.113
|
0.347
|
<0.001
|
Tumor location
|
|
|
|
|
0.001
|
|
Central
|
1(REF)
|
|
|
|
|
UIQ
|
0.508
|
0.264
|
0.975
|
0.042
|
|
LIQ
|
0.493
|
0.183
|
1.332
|
0.163
|
|
UOQ
|
0.603
|
0.400
|
0.909
|
0.016
|
|
LOQ
|
0.615
|
0.305
|
1.239
|
0.174
|
|
Nipple
|
0.631
|
0.328
|
1.212
|
0.167
|
|
Other
|
0.522
|
0.352
|
0.776
|
0.001
|
|
Overlapping
|
0.497
|
0.342
|
0.722
|
<0.001
|
Tumor stage
|
|
|
|
|
<0.001
|
|
T1
|
1(REF)
|
|
|
|
|
T2
|
5.877
|
4.463
|
7.739
|
<0.001
|
|
T3
|
25.211
|
11.632
|
54.643
|
<0.001
|
|
T4
|
60.418
|
32.409
|
112.631
|
<0.001
|
Pathological type
|
|
|
|
|
0.024
|
|
IDC
|
1(REF)
|
|
|
|
|
ILC
|
0.405
|
0.090
|
1.832
|
0.241
|
|
ADENO-CA
|
0.355
|
0.176
|
0.716
|
0.004
|
|
Paget
|
1.512
|
0.457
|
4.997
|
0.498
|
|
Other
|
0.542
|
0.186
|
1.577
|
0.261
|
Histologic grade
|
|
|
|
|
<0.001
|
|
I
|
1(REF)
|
|
|
|
|
II
|
2.569
|
1.555
|
4.245
|
<0.001
|
|
III
|
7.240
|
4.335
|
12.093
|
<0.001
|
Constant
|
|
0.126
|
|
|
<0.001
|
Establishment of a prediction model for ALNM
A nomogram to predict ALNM was developed in the training cohort (Figure 1). The nomogram that incorporated the following independent predictors were shown to be associated with ALNM including age, pathological type, tumor location, histologic grade, and tumor stage. The weights of each variable in the nomogram corresponded to different points. Points for the following factors were added to the total points, which corresponded to the linear predictors and risk predictors of ALNM: age, histological(pathological type), Site(tumor location), Grade(histologic grade), and T-stage (tumor stage).
ROC curves of the training cohort are plotted in Figure 2A. AUC were 0.846 (95% CI 0.825-0.867).The nomogram demonstrated good accuracy for predicting ALN, with an unadjusted C-index of 0.848 (95% CI, 0.807 - 0.889).To test the performance of the nomogram, 1,000 bootstrap resampling was carried out for verification through the calibration chart in the training cohort (Figure 2B). The calibration curve indicated a good calibration effect of the nomogram. These results indicated that the nomogram is a useful predictor for ALNM.
The predictive ability of nomograms in the validation cohort
This nomogram was prospectively used for patients in the validation cohort. It depicts the ROC curve(Figure 2C), and the AUC value calculated was 0.848(95% CI,0.819-0.877), indicating a good predictive ability. The nomogram was internally verified using the bootstrap (1000 bootstrap resamples) validation method. Good calibration was observed for the probability of ALNM in the validation cohort(Figure 2D).To further evaluate the clinical value of the model under different risks of ALNM. We select 14 cutoffs according to the Jordan index. The number of patients, number of patients with ALNM, sensitivity, specificity, accuracy, and negative predictive value of ALNM were calculated under different predicted risk values. (Table 4). As can be seen from the table, this model is more accurate in predicting patients with negative axillary lymph nodes. There were 204 cases with a predicted risk of <10%, and only 14 (6.9%) had ALNM, indicating that the model was more accurate in predicting patients with a lower risk of ALNM. The reason for this result is related to the study design. Both the training cohort and the validation group were patients with clinically negative axillary lymph nodes, resulting in a more accurate prediction of negative lymph nodes and a poorer prediction of positive lymph nodes.
Table 4 accuracy of the developed model's prediction in the validation cohort
Predicted
Risk
|
No. of patients(% )
|
No. of patients with
ALN metastasis
|
Sensitivity
( %)
|
Specificity
(% )
|
Accuracy
(% )
|
Negative predictive value (% )
|
<0.051
|
76(8.74)
|
2
|
99.30
|
87.50
|
97.37
|
97.37
|
<0.100
|
204(23.45)
|
14
|
95.00
|
67.80
|
93.14
|
93.14
|
<0.150
|
307(35.29)
|
30
|
89.30
|
53.10
|
90.23
|
90.23
|
<0.202
|
369(42.41)
|
39
|
86.10
|
44.10
|
89.43
|
89.43
|
<0.248
|
437(50.23)
|
54
|
80.70
|
35.10
|
87.64
|
87.64
|
<0.299
|
496(57.01)
|
62
|
77.90
|
26.40
|
87.50
|
87.50
|
<0.353
|
553(63.56)
|
71
|
74.60
|
18.30
|
87.16
|
87.16
|
<0.400
|
568(65.29)
|
76
|
72.90
|
16.60
|
86.62
|
86.62
|
<0.452
|
616(70.80)
|
90
|
67.90
|
10.80
|
85.39
|
85.39
|
<0.501
|
642(73.79)
|
94
|
66.40
|
7.10
|
85.36
|
85.36
|
<0.603
|
708(81.38)
|
144
|
48.60
|
4.40
|
84.46
|
85.36
|
<0.696
|
764(87.82)
|
189
|
32.50
|
2.50
|
84.16
|
85.36
|
<0.803
|
792(91.03)
|
213
|
23.90
|
1.90
|
84.22
|
85.36
|
<0.899
|
817(93.91)
|
230
|
17.90
|
0.50
|
83.72
|
85.36
|