General information
After application of selection criteria, a total of 164 cases were enrolled in analysis: the total recurrence rate of ovarian cancer was 37.1% (61/164) within 3 years.A summary of demographic factors and clinical parameters of patients in this study are shown in Table 1., 92% of cases were epithelial ovarian cancer. According to previous studies, we divided our patients into two groups, which were epithelial ovarian cancer and non-epithelial ovarian cancer respectively. The mean age and pre-surgery serum CA125 was 49.7 years old and 735.3 U/L, and the majority of patients were epithelial ovarian (92.1%) , had an apparent FIGO stage I tumor (68.9%) , didn’t have LSVI (68.9%), liver metastasis (53.7%), and omentum involvement (58.5%), with a statistical significance. Recurrent ovarian cancer patient had higher rates of epithelial ovarian cancer, more advanced FIGO stage, higher level of serum CA125, and presence of LVSI, liver metastasis, and omentum involvement. (all P < 0.05)
Table. 1. Patient and Tumor Characteristics of the Overall Cohort of ovarian cancer Patients, and Characteristics by recurrent status
Variables
|
Overall cohort
(n=164)
|
Relapsed
(n=61)
|
Unrelapsed
(n=103)
|
P
|
Age
|
49.7 ± 14.8
|
55.1 ± 14.0
|
46.5 ± 14.4
|
0.007
|
Histological type
|
|
|
|
0.022
|
Epithelial ovarian
|
151 (92.1%)
|
60 (98.4%)
|
91 (88.4%)
|
|
Other
|
13 (7.9%)
|
1 (1.6%)
|
12 (12.6%)
|
|
FIGO stage
|
|
|
|
< 0.001
|
I
|
113 (68.9%)
|
26 (42.6%)
|
87 (84.5%)
|
|
II
|
10 (6.1%)
|
4 (6.6%)
|
6 (5.8%)
|
|
III
|
29 (17.7%)
|
19 (31.2%)
|
10 (9.7%)
|
|
IV
|
12 (7.3%)
|
12 (19.7%)
|
0
|
|
LSVI
|
|
|
|
< 0.001
|
Yes
|
51(31.1%)
|
38 (62.3%)
|
13 (12.6%)
|
|
No
|
113 (68.9%)
|
23 (37.7%)
|
90 (87.4%)
|
|
liver metastasis
|
|
|
|
< 0.001
|
Yes
|
76 (46.3%)
|
50 (82.0%)
|
26 (25.2%)
|
|
No
|
88 (53.7%)
|
11 (18.0%)
|
77 (74.8%)
|
|
omentum involvement
|
|
|
|
< 0.001
|
Yes
|
68 (41.5%)
|
47 (77.1%)
|
21 (20.4%)
|
|
No
|
96 (58.5%)
|
14 (23.0%)
|
82 (79.6%)
|
|
Serum CA125
|
735.3 ± 2037.2
|
1166.2 ± 2639.9
|
480.1 ± 1534.9
|
< 0.001
|
< 35 U/L
|
49 (29.8%)
|
8 (13.1%)
|
41 (39.8%)
|
|
35 ~ 262.3 U/L
|
55 (41.7%)
|
12 (19.6%)
|
43 (41.7%)
|
|
≥ 262.3U/L
|
60 (36.6%)
|
41 (67.2%)
|
19 (18.5%)
|
|
LVSI: lymphovascular invasion
Development and Evaluation of the Predictive Model
Univariate and multivariate logistic regression analyses were performed on the variables related to recurrence, and the results are summarized in Table 2. The final model included 7 variables that were independently associated with recurrence: age, histological type, FIGO, liver metastasis, omentum involvement, LVSI, and CA125.
The model was verified with 1000 replicates of bootstrapping, and the bias correction measurement values for accuracy were Brier score 0.131, correction slope 1.00, and c-index 0.870. The DCA curve revealed that compared with FIGO models, the hybrid model was more superior in predicting the recurrent rate of patients. And the calibration plot , ROC curves, and DCA curve were also plotted for graphical evaluation of calibration and discrimination, as shown in Figure 1.
C-index tests the discrimination ability of the model, or the ability to distinguish a woman who gives birth prematurely from a woman who gives birth normally. The value ranges from 0.5 to 1, and the closer the value is to 1, the stronger the discriminant ability is. Correction slope tests the consistency between the predicted value and the result with a perfect slope equal to 1. The Brier score is a measure of overall performance that covers both calibration and discrimination. It represents the difference between the predicted probability and the actual outcome. The score ranged from 0 to 1, and the closer the value was to 0, the better the prediction ability. In general, the values obtained by our measurements show a fairly good prediction accuracy.
Table 2. Univariable and Multivariable Analyses of Variables Associated with recurrence
Variable
|
Univariable OR (95% CI)
|
P
|
Multivariable OR (95% CI)
|
P
|
Age
|
2.23 (1.39 -3.57)
|
0.001
|
1.22 (0.66 - 2.25)
|
0.518
|
Histological type
|
0.13 (0.02 - 1.00)
|
0.050
|
0.50 (0.05 - 5.29)
|
0.567
|
FIGO
|
3.02 (2.06 - 4.45)
|
< 0.001
|
1.81 (1.00 -3.27)
|
0.049
|
Liver metastasis
|
5.31(1.79 - 15.75)
|
0.003
|
1.08(0.20 - 5.79)
|
0.930
|
Omentum involvement
|
13.11 (6.10 - 28.18)
|
< 0.001
|
1.58 (0.45 - 5.53)
|
0.038
|
LVSI
|
11.44 (5.25 - 24.92)
|
< 0.001
|
3.00 (1.11- 8.09)
|
0.030
|
CA125
|
|
|
|
|
< 35U/L
|
Reference
|
|
Reference
|
|
35 ~ 262.3 U/L
|
1.43(0.53 - 3.86)
|
0.479
|
0.54 (0.16 - 1.91)
|
0.342
|
> 262.3 U/L
|
11.06(4.35 - 28.10)
|
< 0.001
|
2.17 (0.62 - 7.57)
|
0.224
|
LVSI: lymphovascular invasion
Creation and use of the nomogram
A nomogram diagram is constructed based on the results of the logistic regression model and shows the predictive variables and corresponding point scales, as presented in Figure 2. The steps to use a nomogram are: 1) identify the status of each predictor for pregnant women, 2) draw a straight line from each predicted state upwards to the partial point reference, 3) sum the points corresponding to each predicted state, 4) locate the sum on the total points reference line, and 5) draw a line from the total point line to the bottom risk line to find the probability of recurrence after surgery.
The use of the nomogram can be illustrated by a clinical example. (Figure.3) In the example, we calculate the predicted probability of recurrence for a 50-year-old patient with omentum involvement, preoperative serum CA125 level of 300U/L, and FIGO stage I epithelial ovarian cancer. Points are assigned for each feature: 22.5 for 50 years old, 48 for epithelial ovarian cancer histology, 65 for omentum involvement, 78 for preoperative serum CA125 level of 300U/L. The total of 223.5 points corresponds to a nearly 55% chance of recurrence for this patient.