A nomogram predicting the recurrence of hepatocellular carcinoma in patients after laparoscopic hepatectomy

Background

Hepatocellular carcinoma (HCC) is a leading cause of cancer deaths globally, ranked as the fifth common malignancy and the second leading cause of cancer-related mortality [1, 2]. According to several guidelines, hepatectomy is recommended as a curative treatment for patients with solitary liver cancer and well-preserved liver function [3, 4]. Despite curative resection, the long-term prognosis of HCC patients is still unsatisfactory, with an extremely high recurrence rate exceeding 70% at 5 years, even in patients with HCC of size ≤ 5 cm [5, 6]. It is believed that the limitations of hepatectomy result in potential HCC recurrence due to residual cancer in the remnant liver or the possibility of de novo HCC recurrence induced by hepatitis B virus infection [7]. To ensure the appropriate management of patients after HCC resection for optimal survival prolongation, data on clinical, surgical, and pathological characteristics should be conjointly used for accurate survival prognostication to optimize individualized treatment planning.

Recent studies on laparoscopic surgery have consistently shown comparable outcomes to conventional surgery for hepatectomy in treating HCC, meanwhile, laparoscopic hepatectomy (LH) also possesses the advantages of having minimal surgical invasiveness and faster recovery [8, 9]. Although the recurrence rates of patients who underwent laparoscopic and conventional hepatectomy are similar, with 3-year disease-free survival rates ranging from 72.5% to 50%, prognostic factors for recurrence in these two groups of patients differ because of differentiation in patient selection for surgery and the operating techniques used [8]. To this end, Li et al. [9], Nakagawa et al. [10], and Umeda et al. [11] developed scoring systems for patients subjected to conventional hepatectomy to evaluate their recurrence probabilities, based on clinical and pathological variables. To develop the most cost-effective, postoperative surveillance protocol, there is a need to stratify the risks of recurrence in HCC patients after LH. However, few scoring systems have focused on laparoscopic hepatectomy (LH) for predicting recurrence-free survival (RFS).

Currently, the 8th edition of the American Joint Committee on Cancer (AJCC) tumor-node-metastasis (TNM) staging system and the Barcelona Clinic Liver Cancer (BCLC) Classification are based on the pathological information, and the treatment regimens for HCC patients are established according to these staging systems [10, 11]. Several studies pointed out that patients who were allocated to the same treatment according to similar disease characteristics had completely different clinical outcomes [10, 12]. This indicated that the present staging systems are inadequate for predicting recurrence and do not accurately reflect the biological heterogeneity of HCC patients. Therefore, a comprehensive, easy-to-use tool able to estimate individual risk by incorporating pathological and clinical factors could serve as a valuable decision-making tool for clinicians.

The aim of this study was to formulate and validate a predictive model capable of predicting the RFS of HCC patients after LH which in turn can be used to guide individualized post-LH surveillance protocols.

Methods

Results

Development and validation of the nomogram model

Kaplan–Meier estimates of RFS in the training and validation cohorts are presented in Fig. 1. In the training cohort, 156 (48.15%) patients developed recurrence during a median follow-up of 13.58 months (interquartile range [IQR], 4.49–26.41 months), and the 1-, 2-, and 3-year RFS rates were 62.1%, 49.0%, and 42.5% with a median RFS after primary LH of 23.6 months (Fig. 1a).

Univariate analyses (Table 2) revealed that positive HBsAg (P=0.008), presence of liver macronodular cirrhosis (P=0.006), elevated AFP (P<0.001), increased AST (P<0.001) and ALT (P=0.018), greater amount of bleeding (P=0.002), larger tumor size (P<0.001), 2–3 lesions (P<0.001), low cancer cell differentiation (P=0.001), presence of tumor thrombus (P<0.001), MVI (P<0.001), absence of tumor encapsulation (P=0.010), and unclear tumor boundary (P<0.001) were identified as significant prognostic factors for RFS. In multivariate analysis, HBsAg (hazard ratio [HR], 1.838; 95% confidence interval [CI] 1.016–3.327; P=0.044), tumor number (HR, 1.774; 95% CI 1.223–2.573; P=0.003), tumor thrombus (HR, 2.356; 95% CI 1.344–4.130; P=0.003), cancer cell differentiation (HR, 0.745; 95% CI 0.535–1.036; P=0.080), and the presence of MVI (HR, 1.673; 95% CI 1.150–2.433; P=0.007) were identified as independent predictors for RFS (Table 2).

Table 2. Cox proportional hazards regression analyses of recurrence in the training cohort

Variable	Total (cases)	Events (cases)	Univariate analysis		Multivariate analysis
			HR (95% CI)	P value	Estimated coefficient	HR (95% CI)	P value
Age (years)			0.738 (0.471–1.156)	0.233
< 65	281	139
≥ 65	43	17
Sex			0.966 (0.580–1.609)	0.895
Male	285	140
Female	39	16
Hepatitis B surface antigen			2.070 (1.363–3.146)	0.008	0.609	1.838 (1.016–3.327)	0.044
Yes	276	142
No	48	14
Liver macronodular cirrhosis			1.741 (1.235–2.455)	0.006	0.125	1.133 (0.814–1.575)	0.460
None	87	33
Light	226	121
Medium	8	1
Heavy	3	1
AFP (ng/mL)			1.712 (1.242–2.361)	< 0.001	0.128	1.137 (0.793–1.629)	0.485
< 200	182	74
≥ 200	142	82
CA19-9 (ng/mL)			1.359 (0.920–2.009)	0.092
< 35	248	116
≥ 35	76	40
AST (IU/L)			1.930 (1.226–3.039)	< 0.001	0.122	1.129 (0.673–1.895)	0.646
< 50	266	119
≥ 50	58	37
ALT (IU/L)			1.516 (1.039–2.213)	0.018	0.285	1.329 (0.866–2.041)	0.193
< 50	246	109
≥ 50	78	47
Hemoglobin (g/L)			0.733 (0.472–1.140)	0.124
< 130	55	30
≥ 130	269	126
Albumin (g/dL)			0.819 (0.176–3.812)	0.778
< 35	5	2
≥ 35	319	154
Bilirubin (mg/dL)			1.157 (0.770–1.737)	0.461
< 17.1	260	124
≥ 17.1	64	32
Platelet count (*103/mm3)			0.610 (0.250–1.490)	0.168
< 80	14	8
≥ 80	310	148
Prothrombin time (INR)			–	0.070
≤ 0.85	3	0
0.85–1.2	313	151
> 1.2	8	5
HBV-DNA copy number (Log)			1.183 (0.863–1.621)	0.301
< 2	142	64
≥ 2	182	92
Bleeding (mL)			2.139 (1.090–4.197)	0.002	0.550	1.734 (0.872–3.446)	0.117
< 800	299	138
≥ 800	25	18
Operation time (min)			1.194 (0.769–1.855)	0.400
< 200	273	129
≥ 200	51	27
Portal vein embolization			1.407 (1.000–1.980)	0.400
Yes	107	59
No	217	97
Tumor size (cm)			2.175 (1.570–3.012)	< 0.001	0.208	1.231 (0.809–1.872)	0.332
< 5	184	69
≥ 5	140	87
Tumor number			2.324 (1.592–3.392)	< 0.001	0.573	1.774 (1.223–2.573)	0.003
Single	236	94
2–3 lesions	88	62
Cancer cell differentiation			0.615 (0.446–0.849)	0.001	− 0.295	0.745 (0.535–1.036)	0.080
Low	162	90
Medium	151	64
High	11	2
Tumor thrombus			4.126 (1.856–9.170)	< 0.001	0.857	2.356 (1.344–4.130)	0.003
Yes	29	23
No	295	133
MVI			2.291 (1.646–3.189)	< 0.001	0.514	1.673 (1.150–2.433)	0.007
Yes	136	85
No	188	71
Surgical procedure			1.108 (0.444–2.764)	0.718
Irregular	200	97
Regular	124	59
Tumor encapsulation			0.978 (0.639–1.498)	0.010	− 0.079	0.924 (0.753–1.135)	0.453
Absent	119	63
Incomplete	79	43
Complete	126	50
Tumor boundary			2.343 (1.204–4.559)	< 0.001	− 0.016	0.985 (0.535–1.814)	0.960
Clear	295	136
Unclear	29	20

• HR hazard ratio, CI confidence interval, AFP = alpha fetoprotein, CA19-9 carbohydrate antigen 19-9, AST aspartate transaminase, ALT aminotransferase, INR international normalized ratio, HBV hepatitis B virus, MVI microvascular tumor invasion

The prognostic nomogram that integrated all the independent prognostic factors for RFS derived from the training cohort is shown in Fig. 2. The C-index for RFS prediction in the training and validation cohorts were 0.703 (95% CI 0.747–0.659) and 0.789 (95% CI 0.858–0.719), respectively. The calibration plot for the RFS probability in the training and validation cohorts at 3 years after LH showed acceptable consistency between the prediction by nomogram and actual observation (Fig. 3).

ROC analysis among nomogram, 8th AJCC TNM, and BCLC

We compared the accuracy and probability of our nomograms with the clinically used prognostic models, namely the 8th AJCC TNM classification and the BCLC staging system. ROC curves for the 3-year RFS were plotted for the 108 patients in the validation cohort. The discriminatory ability of the present nomogram model, which had a C-index corresponding to the area under the ROC curve of 0.786 (95% CI 0.698–0.875), was superior to that of the 8th AJCC TNM classification and the BCLC staging system with C-indexes of 0.698 (95% CI 0.596–0.799) and 0.632 (95% CI 0.542–0.722), respectively (Fig. 4). According to the ROC analysis, we observed an improved predictive benefit in RFS and higher threshold probability when using our proposed nomogram as compared to the other predictive systems.

Discussion

In the present study, we developed and validated a practical nomogram model, based on clinicopathological characteristics of HCC patients who underwent LH, to predict the 1-, 2-, and 3-year RFS. It demonstrated superior prognostication performance compared with the 8th AJCC TNM classification and the BCLC staging system (C-index, 0.786 vs. 0.698 vs. 0.632, respectively).

It is widely believed that poor liver function and heavy tumor burden are significant prognostic factors that are associated with tumor recurrence after hepatectomy in HCC patients [15–17]. Compared to non-resection treatment, such as radiofrequency ablation, interventional therapy, and radiotherapy, establishing staging systems that are based on postoperative pathology combined with clinical factors seems more reliable for the prediction of recurrence, as it possesses more accurate and reliable information on tumor profiles as to that provided solely by postoperative pathology. However, almost all previously established staging systems are based on conventional hepatectomy which is much invasive to patients, and predictive model based per-patient is limited [18, 19]. Traditional opinions suggest that the evaluation of conventional hepatectomy is more depended on liver profiles that contribute more for long-term survival [18], whereas laparoscopic hepatectomy has comparable clinical outcomes to conventional hepatectomy and is less invasive, thereby reducing the injury to liver function for patients who are subjected to hepatectomy [20]. Simultaneously, this change of surgical selection increases the role of tumor burden in the prediction of recurrence for patients who are treated with LH. As a result, LH has different intrinsic properties from that of open procedure, and their long-term outcomes need to be separately mapped.

Several studies have emphasized the critical roles of tumor burden, gender, liver function, and performance status in the prognosis of HCC, but few have actually shown the role of detailed information of pathology in prognosis prediction [12, 21]. It is commonly supposed that the 8th AJCC TNM classification is one of the most prevalent staging systems of HCC, which is composed of TNM stage. However, this only classifies tumor burden and is limited in the power of prediction for HCC patients who are subjected to LH [22]. HCC patients who undergo surgical resection rarely suffer from lymph node metastases or distant metastases, and this classification thereby influences the accurate evaluation of RFS. The BCLC staging system takes both the liver function and tumor characteristics into account, including tumor extension, reserved liver function, physical status, and cancer-related symptoms [23]. The notable feature that distinguishes the BCLC staging system from other systems is the treatment recommendations for each stage based on the best treatment options currently available [24]. However, the BCLC class B (intermediate stage) covers a considerable heterogeneous population of HCC patients with varying degree of tumor extension, reserved liver function, and disease etiology, thus resulting in prognostic heterogeneity and preventing the decision of optimal treatment regimen selection. Meanwhile, the guidelines mentioned above are mainly based on preoperative clinical data or pathological information. Moreover, no guideline tailors for resectable HCC patients who were subjected to LH. Therefore, it is urgent to introduce a reliable, practicable, and individualized predictive model for patients who are candidates for surgical hepatectomy, especially LH.

The present nomogram integrates five independent risk factors for RFS, including HBsAg, tumor thrombus, tumor number, cancer cell differentiation, and MVI. Many studies have indicated that HBV infection, tumor thrombus, and MVI were significant risk factors for recurrence in patients with HCC [25–27]. The underlying hepatitis background was significantly associated with late recurrence and multicentric carcinogenesis. Tang et al. [27] reported that HBV infection might accelerate hepatocarcinogenesis via the integration of HBV DNA into the host genome, and continuous expression of viral proteins such as HBx might be involved in hepatocarcinogenesis. However, the major source of early recurrence is generally thought as metastasis, which is mainly derived from vascular invasion. Hirokawa et al. [25] indicated that circulating tumor cells were closely related to epithelial–mesenchymal transition and mesenchymal–epithelial transition which are the significant property of cancer stem cells. Given the early diagnosis of HCC, tumor thrombus is rare. Alternately, MVI is another potent parameter indicating vascular invasion for the prediction of recurrence [28]. Additionally, the present study demonstrated that tumor number predicted HCC recurrence, which was consistent with the results of other studies [29, 30]. However, tumor size could not be included in the nomogram proposed for HCC recurrence prediction in the present study, although other studies have indicated its insightful role in prognostic prediction [31, 32]. The possible explanation is that vascular invasion plays a more critical role in recurrence than tumor size, especially for patients with tumor size > 2 cm, according to 8th AJCC TNM classification [14, 33]. Besides, surgical margin was also not included in the nomogram, and it could be explained in the way that the patients included in the present study all had a minimal surgical margin of 1 cm, which indicated better RFS [13]. Interestingly, cancer cell differentiation was found to be a significant prognostic factor, and this was rarely mentioned in other studies. Low cancer cell differentiation has been reported to be the property of cancer progenitor or cancer stem cells which has high malignant biological behavior [34].

As the clinical and pathological factors mentioned in the present study have been validated separately in previous conventional hepatectomy studies, and the present study is the first to combine them together to assess patients who are subjected to laparoscopic hepatectomy. Hence, the proposed nomogram can be used to better guide routine follow-up for patients who have undergone LH as initial therapy. Patients characterized with a high recurrence score on our nomogram could be counseled to receive more high-end imaging examinations and close follow-up. In addition, more aggressive adjuvant therapy might be proposed, even if the results of the latest postoperative examinations indicated no evidence of recurrence. Conversely, the follow-up period for low-risk patients should refer to the clinical guideline [3].

Although our nomogram demonstrated satisfactory performance compared with existing systems used clinically, its related limitations need to be described. First, the nomogram was derived from data collected at a single institution, and the follow-up duration was relatively short for prognosticating long-term survival outcomes. Second, as this is a retrospective study for predicting the anticipated result, our nomogram needs to be confirmed in a prospective cohort. Third, our nomogram is mainly based on pathological outcomes, therefore, it is inapplicable to evaluate non-surgical patients.

Conclusions

We proposed a nomogram for predicting the postoperative RFS for HCC patients who underwent LH, based on easy-to-obtain clinical factors, comprising of HBsAg, tumor thrombus, tumor number, cancer cell differentiation, and MVI. The nomogram demonstrated relatively higher prediction than conventional 8th AJCC TNM and BCLC staging systems, and these findings, after proper validation, can be used as a model to better to guide individualized post-LH surveillance protocols of such patients.

Funding

This work was supported by the National Natural Science Foundation of China (No. 81602143), National 135 Major Project of China (2018ZX10723204; 2018ZX10302205) and Sun Yat-sen University Cancer Center physician scientist funding (No. 16zxqk04).

Authors’ contributions

YXP, JCC, and APF designed experiments and drafted the manuscript. XHW, JBC, WH, and JCW were responsible for data collection and statistical analysis. QJL, ZGZ, YZF, LX, MSC, and YJZ revised the manuscript and all authors agreed to be responsible for all aspects of the study. All authors read and approved the final manuscript.

Availability of data and materials

The datasets analyzed during the current study are available in the Research Data Deposit (RDD) repository (http://www.researchdata.org.cn/; RDD Number: RDDA2019001113).

Ethics approval and consent to participate

The study protocol was approved by the Clinical Research Ethics Committee of SYSUCC, and all patients provided written informed consent. (B2019-129-01).

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.