Characteristics of patients and disease
A total of 810 children diagnosed with hepatoblastoma between 2000 and 2018 were identified from the SEER database. Boys accounted for 61.6% (n=499) of the patients and girls for 38.4% (n=311), with a male-to-female ratio of 1.6 (Table 1). There were 641 children ≤ 2 years old and 169 children > 2 years old. We found that the overall incidence of hepatoblastoma increased from 2000 to 2018, and the APC was 1.63% (95% CI: -0.6% to 3.9%, P<0.05). Boys had a higher incidence than girls. The incidence of girls has increased in recent years, and the APC was 3.01% (95% CI: -1.0% to 7.2%, P<0.05). The incidence rate of African American children had increased, and the APC was 55.64% (95% CI: 1.0% to 139.9%, P<0.05). The incidence rate of children aged under 2 years old was higher than that of other age groups, and the APC was 5.39% (95% CI: 0.5% to 10.5%, P<0.05) (Figure 1).
Table 1: Characteristics of children with hepatoblastoma who were included in the study
Characteristic
|
Whole population
[cases (%)]
|
Training cohort
[cases (%)]
|
Validation cohort
[cases (%)]
|
P value
|
Total
|
n=810
|
n=568
|
n=242
|
|
Sex 0.3781
|
Female
|
311 (38.40)
|
212 (37.32)
|
99 (40.91)
|
|
Male
|
499 (61.60)
|
356 (62.68)
|
143 (59.09)
|
|
Race 0.6667
|
White
|
616 (76.05)
|
436 (76.76)
|
180 (74.38)
|
|
Black
|
70 (8.64)
|
46 (8.10)
|
24 (9.92)
|
|
Other
|
124 (15.31)
|
86 (15.14)
|
38 (15.70)
|
|
Age 0.8489
|
0-2 years old
|
641 (79.14)
|
451 (79.40)
|
190 (78.51)
|
|
>2 years old
|
169 (20.86)
|
117 (20.60)
|
52 (21.49)
|
|
Diagnosis year 0.6199
|
2000-2009
|
384 (47.41)
|
273 (48.06)
|
111 (45.87)
|
|
2010-2018
|
426 (52.59)
|
295 (51.94)
|
131 (54.13)
|
|
Tumor_stage 0.4695
|
Local
|
377 (46.54)
|
257 (45.25)
|
120 (49.59)
|
|
Reginal
|
244 (30.12)
|
173 (30.46)
|
71 (29.34)
|
|
Distant
|
189 (23.33)
|
138 (24.30)
|
51 (21.07)
|
|
AFP 1.0
|
Positive
|
786 (97.04)
|
551 (97.01)
|
235 (97.11)
|
|
Negative
|
24 (2.96)
|
17 (2.99)
|
7 (2.89)
|
|
Tumor_size 1.0
|
≤5cm
|
172 (21.23)
|
121 (21.30)
|
51 (21.07)
|
|
>5cm
|
638 (78.77)
|
447 (78.70)
|
191 (78.93)
|
|
Surgery_type 0.9933
|
No surgery
|
152 (18.77)
|
106 (18.66)
|
46 (19.01)
|
|
Liver resection
|
527 (65.06)
|
370 (65.14)
|
157 (64.88)
|
|
Liver transplantation
|
131 (16.17)
|
92 (16.20)
|
39 (16.12)
|
|
Chemotherapy 1.0
|
Yes
|
740 (91.36)
|
519 (91.37)
|
221 (91.32)
|
|
No
|
70 (8.64)
|
49 (8.63)
|
21 (8.68)
|
|
Status 0.7172
|
Alive
|
644 (79.51)
|
454 (79.93)
|
190 (78.51)
|
|
Dead
|
166 (20.49)
|
114 (20.07)
|
52 (21.49)
|
|
Survival_time
|
61.5[18.0, 120.75]
|
65.0[19.0, 123.25]
|
56.0[17.0, 110.0]
|
0.229
|
Nomogram variable screening
The COX univariate regression analysis showed that risk factors for pediatric hepatoblastoma were race, age, tumor stage, tumor size, surgery type, and chemotherapy (P < 0.05) (Table 2). The LASSO univariate regression analysis indicated that the risk factors were sex, age, diagnosis year, tumor stage, tumor size, surgery type, and chemotherapy (Figures 2a, 2b). The BSR univariate regression analysis showed that the risk factors were sex, age, diagnosis year, tumor size, surgery type, and chemotherapy (Figure 2c). The results of the three univariate analyses were included in COX multivariate regression, and the independent risk factors for hepatoblastoma were determined. The AUC of COX (AIC=1264, Figure 3a) and BSR (AIC=1260.87, Figure 3b) was 80.2% (Figure 3d). In addition, 80.2% of AUC was superior to LASSO (AIC=1267.96, Figure 3c), and COX was consistent with the independent risk factors identified by the BSR analysis, which included race, age, tumor size, surgery type, and chemotherapy. Therefore, the above variables were used for further analysis and modeling.
Table 2: COX univariate regression analysis for predicting overall survival in children with hepatoblastoma
Variable
|
HR (95% CI)
|
P value
|
Sex
|
Female
|
1.00
|
|
male
|
1.2 (0.82-1.77)
|
0.351
|
Race
|
White
|
1.00
|
|
Black
|
2.22 (1.3-3.79)
|
0.003
|
Other
|
0.87 (0.49-1.53)
|
0.619
|
Age
|
0-2 years old
|
1.00
|
|
>2 years old
|
1.69 (1.13-2.51)
|
0.01
|
Diagnosis_year
|
|
|
2000-2009
|
1.00
|
|
2010-2018
|
0.76 (0.52-1.1)
|
0.146
|
Tumor_stage
|
Local
|
1.00
|
|
Reginal
|
1.44 (0.91-2.26)
|
0.12
|
Distant
|
2 (1.28-3.13)
|
0.002
|
AFP
|
|
|
Positive
|
1.00
|
|
Negative
|
0.95 (0.3-2.99)
|
0.932
|
Tumor_size
|
≤5cm
>5cm
|
1.00
|
|
>5cm
>5cm
|
1.83 (1.08-3.11)
|
0.024
|
Surgery_type
|
No surgery
|
1.00
|
|
Liver resection
|
0.12 (0.08-0.18)
|
0
|
Liver transplantation
|
0.15 (0.08-0.27)
|
0
|
Chemotherapy
|
Yes
|
1.00
|
|
No
|
4.09 (2.58-6.47)
|
0
|
Nomogram construction
R4.1.1 software (the "RMS" package) was used to identify independent risk factors affecting prognosis. The nomogram was constructed and verified by ranking each variable in importance according to the standard deviation of the nomogram scale. Each variable reflects the corresponding point on the relevant variable axis of the column chart, and the point is used as the vertical line of the variable axis to correspond to the upper score scale to obtain the score of the variable. The total score was obtained by summation of the scores for each variable. The total score corresponded to the points on the axis of the 1-, 3-, and 5-year overall survival (OS) rates, which represent the children's predicted survival rate (Figure 4).
The "DynNom" program package in R4.1.1 software was used to create a web-based calculator to realize a dynamic line-graph, allowing for the input of specific variables to calculate the possibility of events and increase the practicability of the line-graph prediction model. Direct access to the application https://yixuexiaodaotong.shinyapps.io/DynNomapp/ can be formulated into our web-based calculator to realize the dynamic model of the nomogram. As shown in Figure 5a, the abscissa represents follow-up time (month) and the ordinate represents survival probability. The network server will then automatically generate the patient's survival probability curve and 95% CI after inputting the patient's clinical data. The OS of the patient can be easily predicted (Figure 5).
Risk stratification based on the nomogram
Finally, we stratified risk based on total points calculated using the nomogram and X-tile software to calculate the optimal truncation value. Children with hepatoblastoma were divided into two risk groups: low risk (total points < 119) and high risk (total points ≥ 119). Kaplan–Meier curves showed significant differences between the two groups (P < 0.0001) (Figure 6).
Nomogram evaluation and validation
The C-index of the training cohort (Figure 7a) and validation cohort (Figure 7b) was plotted over time. A value greater than 0.7 indicated that the line-graph prediction model had a good degree of discriminative ability. The time-dependent AUC of OS at 10 years was calculated, and the OS probability of both the predicted training cohort (Figure 7c) and the validation cohort (Figure 7d) at 10 years was > 0.7, indicating that the line-graph prediction model had a good degree of discriminative ability. The calibration curve was drawn, and the OS curve that was obtained from the prediction model had a high fit degree with the 45° diagonal line in the calibration graph, suggesting a good consistency between the predicted survival rate and the actual survival rate. The training cohort calibration curve for the 3-year survival rate is shown in Figure 7e and for the 5-year survival rate in Figure 7f. The calibration curve for the 3-year survival rate in the validation cohort is shown in Figure 7g and for the 5-year survival rate in Figure 7h. Decision curve analysis was used to evaluate the clinical effectiveness of the model by calculating the net benefit. The farther the decision curve is from the X and Y axes, the more practical the model will be. Decision curves of 3-year and 5-year survival benefits of the training cohort are shown in Figure 7i. Calibration curves to verify the 3-year and 5-year survival benefits of the cohort are shown in Figure 7j.
Survival
The difference in the survival of 0–2 years old children with chemotherapy versus without chemotherapy was statistically significant throughout the survival curve (P < 0.0001). Children aged 0 to 2 years old with chemotherapy had a much longer survival time than children who did not receive chemotherapy. However, for children more than 2 years old, there was no statistically significant difference in survival whether they received chemotherapy or not (P > 0.05) (Figure 8a). Children who received chemotherapy had a significantly longer survival time as the disease progressed than those who did not (P < 0.05) (Figure 8b). The survival times of children with chemotherapy with tumor sizes larger or smaller than 5cm were significantly longer than those of children without chemotherapy (P < 0.05) (Figure 8c). The survival time for children treated nonsurgically with chemotherapy was significantly longer than the survival time for children treated without chemotherapy (P < 0.05). There was no statistically significant difference in survival times between chemotherapy and no chemotherapy for children who underwent hepatectomy or liver transplantation (P > 0.05) (Figure 8d). Children with chemotherapy treated with hepatectomy and without surgery had significantly longer survival times for tumors ≥ 5cm, compared to nonchemotherapy patients (P < 0.05). The survival time for patients treated with liver transplantation with and without chemotherapy was not significantly different (P > 0.05). For tumors < 5cm, the survival time without surgical treatment was significantly longer with chemotherapy than without chemotherapy (P < 0.05). The survival times for hepatectomy and liver transplantation were not significantly different with or without chemotherapy (P > 0.05) (Figure 8e).