Baseline characteristics
Table 1 shows detailed baseline characcteristics of all patients. Of all patients included, PG 1, PG 2, and PG 3 of HCC were diagnosed in explanted tissue of 324/869 (37.3%), 327/869 (37.6%), 218/869 (25.1%) patients, respectively, in center 1; 17/226 (7.5%), 127/226 (56.2%), 82/226 (36.3%), respectively, in center 2; and 43/200 (21.5%), 74/200 (37.0%), 83/200 (41.5%), respectively, in center 3.
Table 1
The clinical and histologic characteristics of patients from three medical centers.
Characteristics | Cohorts |
Center 1 (n = 869) | Center 2 (n = 226) | Center 3 (n = 200) |
Imaging, n (%) | | | |
CT | 686 (78.9) | 189 (83.6) | 66 (33.0) |
MRI | 183 (21.1) | 37 (16.4) | 134 (67.0) |
Age, n (%) | | | |
< 55yrs | 426 (49.0) | 112 (49.6) | 124 (62.0) |
≥ 55yrs | 443 (51.0) | 114 (50.4) | 76 (38.0) |
Sex, n (%) | | | |
Male | 730 (84.0) | 177 (78.3) | 173 (86.5) |
Female | 139 (16.0) | 49 (21.7) | 27 (13.5) |
HBV/HCV, n (%) | | | |
Absent | 121 (13.9) | 64 (28.3) | 12 (6.0) |
Present | 748 (86.1) | 162 (71.7) | 188 (94.0) |
Child-Pugh | | | |
A | 772 (89.0) | 184 (81.4) | 126 (96.0) |
B/C | 96 (11.0) | 42 (19.6) | 8 (4.0) |
AFP, n (%) | | | |
< 400 ng/mL | 568 (65.4) | 159 (70.4) | 109 (54.5) |
≥ 400 ng/mL | 301 (34.6) | 67 (29.6) | 91 (45.5) |
ALB (g/L), n (%) | | | |
< 40 g/L | 384 (44.2) | 156 (69.0) | 80 (40.0) |
≥ 40 g/L | 485 (55.8) | 70 (31.0) | 120 (60.0) |
TB (umol/L), n (%) | | | |
< 17.1 umol/L | 533 (61.3) | 93 (41.2) | 137 (68.5) |
≥ 17.1 umol/L | 336 (38.7) | 133 (58.8) | 63 (31.5) |
ALBI, n (%) | | | |
low: ≤ -2.60 | 379 (43.6) | 157 (69.5) | 81 (40.5) |
high: > -2.60 | 490 (56.4) | 69 (30.5) | 119 (59.5) |
PT (s), n (%) | | | |
< 13 s | 442 (50.9) | 30 (13.3) | 88 (44.0) |
≥ 13 s | 427 (49.1) | 196 (86.7) | 112 (56.0) |
Tumor size, n (%) | | | |
< 5 cm | 441 (50.7) | 81 (35.8) | 35 (17.5) |
≥ 5 cm | 428 (49.3) | 145 (64.2) | 165 (82.5) |
pAJCC stage | | | |
I † | 298 (34.3) | - | - |
Ia | 51 (5.9) | 25 (11.1) | 17 (8.5) |
Ib | 117 (13.5) | 37 (16.4) | 42 (21.0) |
II | 179 (20.6) | 67 (29.6) | 31 (15.5) |
III † | 58 (6.7) | 97 (42.9) | 110 (55.0) |
IIIa | 83 (9.6) | - | - |
IIIb | 78 (8.9) | - | - |
IV | 5 (0.5) | - | - |
Surgical no. of tumors, n (%) | | | |
Solid | 721 (83.0) | 205 (90.7) | 171 (85.5) |
2 | 71 (8.2) | 15 (6.6) | 14 (7.0) |
≥ 3 | 77 (8.8) | 6 (2.7) | 15 (7.5) |
Edmondson-Steiner, n (%) | | | |
Ⅰ/Ⅰ-Ⅱ | 395 (45.5) | 100 (44.2) | 92 (46.0) |
Ⅱ-Ⅲ/Ⅲ | 474 (54.5) | 126 (55.8) | 108 (54.0) |
MVI, n (%) | | | |
Absent | 580 (66.7) | 61 (27.0) | 68 (34.0) |
Present | 256 (29.5) | 165 (73.0) | 132 (66.0) |
Pathological Grade, n (%) | | | |
PG 1 (MVI- & ES I/II) | 324 (37.3) | 17 (7.5) | 43 (21.5) |
PG 2 (MVI + or ES III/IV) | 327 (37.6) | 127 (56.2) | 74 (37.0) |
PG 3 (MVI+ & ES III/IV) | 218 (25.1) | 82 (36.3) | 83 (41.5) |
Note. -Unless indicated otherwise, data are number of tumors, with percentages in parentheses. †, Patients were assigned with an overall stag I or III, while the subtype Ia, Ib, IIIa or IIIb was not evaluated at the pathology. Albumin-bilirubin (ALBI) score = 0.085 * albumin (g/L) + 0.66 * log (bilirubin umol/l). HBV = hepatitis B virus; HCV = hepatitis C virus; AFP = serum α-fetoprotein; ALB = albumin; TB = total bilirubin; PT = prothrombin time; MVI = microvascular invasion. |
Radiomic Feature Selection
The presence of APTE (odds ratio [LORs], 1.18; 95% CIs, 1.01 to 1.27), presence of star node (LORs, 0.90; 95% CIs, 0.78 to 1.13), ill-defined margin (LORs, 0.81; 95% CIs, 0.63 to 0.98), presence of TTPVI (LORs, 0.71; 95% CIs, 0.58 to 0.84), tumor size > 5cm (LORs, 0.63; 95% CIs, 0.53 to 0.81) were positively associated with PGs; while completed capsule (LORs, -1.84; 95% CIs, -2.07 to -1.67), well-defined margin (LORs, -1.52; 95% CIs, -1.81 to -1.34), tumor size < 3 cm (LORs, -1.41; 95% CIs, -1.69 to -1.22), and absence of TTPVI (LORs, -0.91; 95% CIs, -1.16 to -0.86) were negatively associated with PGs. The original multinomial regression model resulted in an AUC of 0.78 (95% CIs, 0.70–0.81), 0.64 (95% CIs, 0.58–0.72) and 0.87 (95% CIs, 0.84–0.91) for PG 1, PG 2, and PG 3, respectively, on training data (Fig. 1a). On internal test, the model resulted in an AUC of 0.79 (95% CIs, 0.71–0.83), 0.60 (95% CIs, 0.55–0.70) and 0.86 (95% CIs, 0.83–0.91) (Fig. 1b), respectively.
The classification model was transformed into a graphically illustrated diagnostic scheme. As shown in Fig. 2a and Fig. 2b, LTIS uses a five-point LTIS risk score to interpret probability of high pathological grade by combining independent imaging features determined at regression model. Inter-reader agreements of LTIS were assessed in randomly selected in 494 CT datasets and in 183 MRI datasets. LTIS shows good inter-reader agreements in both CT and MRI datasets, with a Cronbach's alpha coefficient of 0.86 (95% CIs, 0.83–0.89) and 0.85 (95% CI, 0.81–0.89), respectively.
Prediction Model Development and Validation
The incidence of “ground truth” PGs stratified by LTIS is depicted in Fig. 3a, with significant linear trends in incidence of PGs across LTIS scores (Cochran Armitage chi-square, p < 0.01). The distribution of pathological findings by LTIS categories in three sub cohorts is illustrated in Suppl Fig. 2. Using LTIS 3 as threshold (≥ 3) for diagnosing PG 2–3, sensitivity, specificity, positive predictive value, and negative predictive value is 73.3% (658/910), 73.2% (282/385), 86.5% (658/761), and 52.8% (282/534), respectively. Compared to conventional clinical factors such as age, sex, and serum biomarkers, the LTIS outperformed them with significantly higher impact index at the random forest analysis by measuring decrease in accuracy (Fig. 3b). Moreover, with the decision curve analysis, adding LTIS to these clinical variables produced obviously higher net clinical benefits for the evaluation of PG (Fig. 3c).
Net Clinical Benefit of LTIS Score on Postsurgical Prognosis
Among the patients entirely followed up, 482 patients presented with a recurrence after liver resection, with a median RFS of 25.3 months (95% CIs, 20.4–27.8 months). 255 patients died after the curative resection, with a median OS of 74.5 months (95% CIs, 54.4–81.4 months). A scatter plot between RFS and OS in subgroups of LTIS score 1 to 5 is summarized in Fig. 4. It shows that patients with higher LTIS score trended to has lower median RFS and lower median OS. In subgroup (n = 395) within 1-year recurrence and 2-year death after surgery, 51.1% (202/395) of patients had LTIS score 4 and score 5.
At the stepwise Cox’s proportional hazard model, the male (hazards ratio [HR], 1.45; 95% CIs, 1.11–1.90; p = 0.006), aspartate aminotransferase (AST) ≥ 40 U/L (HR, 1.32; 95% CIs, 1.09–1.59; p = 0.004), α-fetoprotein (AFP) ≥ 400 ng/mL(HR, 1.56; 95% CIs, 1.29–1.89; p < 0.001), total bilirubin (TB) ≥ 17.1 umol/L (HR, 0.75; 95% CIs, 0.62–0.91; p = 0.004), LTIS score 3–5 (HR, 1.30; 95% CIs, 1.03–1.65, p = 0.026), AJCC III/IV (HR, 1.56; 95% CIs, 1.21–2.01, p < 0.001) and PG 3 (HR, 1.36; 95% CIs, 1.02–1.82, p = 0.038) were identified as independent predictors of RFS. The resulting Cox model with independent predictors produces a C-index of 0.71 (95% CIs, 0.68–0.76) for predicting RFS (Suppl Fig. 3a). The AST ≥ 40 U/L (HR, 1.51; 95% CIs, 1.14–2.00; p = 0.004), AFP ≥ 400 ng/mL (HR, 1.38; 95% CIs, 1.06–1.80; p = 0.017), LTIS score 3–5 (HR, 1.76; 95% CIs, 1.23–2.50, p = 0.002), AJCC III/IV (HR, 3.03; 95% CIs, 2.14–4.30, p < 0.001) and PG 3 (HR, 2.00; 95% CIs, 1.32–3.00, p < 0.001) were identified as independent predictors of OS. The resulting Cox model produces a C-index of 0.76 (95% CIs, 0.72–0.79) for predicting OS (Suppl Fig. 3b). Specially, in patients with tumor size < 3 cm (n = 372), AFP < 40 ng/mL (n = 548), and AJCC stage T1 (n = 587), the rate of LTIS score 3–5 was 27.2%, 47.4% and 35.6% (Fig. 5a). HCC patients at AFP < 40 ng/mL and AJCC stage T1 restaged by LTIS represented with significantly (Log-rank test, p < 0.001) different RFS and OS at Kaplan-Meier survival curve analysis (Fig. 5b and Fig. 5c).