Hepatocellular carcinoma (HCC) with bile duct invasion were far more rarely than that with vascular invasion. Because of the rare incidence of BDTT, there is insufficient data to systematically analyze the prognostic implications of BDTT. However, many studies supported the hypothesis that the prognosis of HCC with BDTT can be worse than HCC without invasion [8–10]. HCC with BDTT had more advanced stage HCC with adverse histological features including higher rates of MVI and poor differentiation [5–7]. Liu et al. also reported that Patients with BDTT extending to the common bile duct usually have an unfavorable prognosis even following aggressive surgery [27]. Although Meng et al. had showed that macro-BDTT but not micro-BDTT was an independent risk factor affecting the prognosis of patients with HCC, the number of HCC patients with micro-BDTT (only 7 patients) was too small [28]. More importantly, Kim et al. demonstrates that the prognosis of HCC patients with micro-BDTT was worser than those without BDTT [29]. The presence of micro-BDTT should therefore be considered as an adverse prognostic factor after hepatectomy.
Surgical treatment for HCC is considered as the most effective approach, including those with BDTT, and the surgical strategy in HCC with BDTT is not clearly defined in previous studies [30–32]. However, Kasai et al. had showed that in HCC patients with BDTT alone without MVI, extended hepatectomy provided a better prognosis [31]. In addition, neoadjuvant TACE reduced the surgical risk of curative liver resection and significantly prolonged median survival in HCC with BDTT [32]. Luo et al had also showed that for HCC patients with BDTT, radical hepatic resection and removal of BDTT, combined with TACE, are the best approach [33]. Peng et al. had reported that curative resection for HCC with BDTT can result in prolonging the survival [34]. These results indicated that the choice of the most appropriate therapeutic strategy is very important for the prognosis of HCC with BDTT. However, misdiagnosis of BDTT before surgery may lead to inappropriate treatments, resulting in poor survival of those patients. In our data, only 2 of 46 HCC patients with micro-BDTT were preoperative diagnosis.
Previous studies have reported that BDTT could appear even in early stage of HCC, and it could also occur in HCC patients with tumor’s diameter less than 3 cm, which indicated that the size of HCC tumor is not correlated with the occurrence of BDTT [27, 35]. In our data, we also found that the size of HCC tumor is not correlated with the occurrence of micro-BDTT. In HCC with BDTT, obstructive jaundice is a main clinical manifestation with higher preoperative bilirubin level, because of biliary tract invasion, and there were always biliary ducts dilatation. These can be used to distinguish HCC with BDTT from those without BDTT. However, the features are also observed in other biliary tract diseases, such as hepatic insufficiency, extrahepatic cholangiocarcinoma, choledochal cyst and common bile duct stone [15]. Besides, because invasion of or tumor thrombus was in the second and more peripheral branches of the bile duct, serum total bilirubin and direct bilirubin in HCC with micro-BDTT were always in the normal range, or slightly higher than normal. In addition, HCC with micro-BDTT were always ignored in dynamic contrast-enhanced CT or MRI. In our data, all patients with micro-BDTT had not clinical symptoms of jaundice. The DB in HCC with micro-BDTT were only slightly higher than that in HCC without BDTT. Therefore, HCC with micro-BDTT were hard to diagnose before surgery, since it had no visible symptoms.
With increasing knowledge, inflammation plays an essential role in tumorigenesis and progression including HCC. As more than 90% of HCC occur with hepatic injury and inflammation, the progression of HCC was inflammation-related carcinogenesis events [36]. The predictive role of systemic inflammation and hepatic inflammation markers in the prognosis of HCC received more attention in recent years. Systemic inflammatory indexes such as NLR, PLR, LMR, SII, and PNI are emerging as predictors of prognosis, tumor grade or MVI in HCC [23]. In our study, the optimal cut-off points for NLR, PLR, LMR, PNI were determined by ROC analysis, which were 1.409, 111.258, 3.338, 53.417, respectively. Herein, we found that pre-treatment NLR and PNI level were significantly associated with micro-BDTT. Through multifactor analysis, pre-treatment PNI level was also an independent predictor of HCC with micro-BDTT. PNI is a marker combinative of albumin and lymphocyte, which has been recognized as an indicator of nutritional and immunological status. Additionally, Chan et al. showed that the PNI was independent prognostic factors for HCC patients [37], and the PNI is a simple and useful systemic inflammation marker for predicting the survival of HCC treated with sorafenib [38]. These results indicated that it is feasible for the PNI as a novel indicator of systemic inflammation. In the present study, the PNI was independent prognostic factors for HCC with micro-BDTT, which was added in the nomogram for predicting micro-BDTT before surgery as a marker of systemic inflammation. However, the specific mechanism of the observations is still unclear.
The background liver inflammation has an important role on the development and prognosis of HCC patients. The clinical indicators of liver inflammation including ALT, AST, ALP and γ-GT had been confirmed to positively related with the recurrence and poor prognosis of HCC patients [39]. The ratio of γ-GT /ALT, another index reflecting liver inflammation, is a powerful prognostic factor for HCC patients. It had found that the ratio of γ-GT /ALT is a convenient prognostic marker for HCC after hepatic resection [25]. In our data, we found that DB, ALP and γ-GT /ALT were significant prognostic factors of micro-BDTT in patients with HCC. However, the exact mechanisms underlying these observations are still unclear. Besides AFP were also identified as independent predictors of HCC with micro-BDTT. In light of these findings, we suggest that HCC patients with lower pre-treatment PNI, higher DB, ALP, AFP and γ-GT /ALT levels may be potential candidates for micro-BDTT before surgery.
Herein, we successfully developed a predictive nomogram for predicting micro-BDTT before surgery in hepatocellular carcinoma based on combining systemic and hepatic inflammation markers. We generalized the sensitivity, specificity, positive predictive value, and negative predictive value in estimating the risk of micro-BDTT. Patients with a high score have a high risk of micro-BDTT. As inflammation-based indexes are routinely available and can be measured accurately, the establishment of a predictive model based on inflammation-based indexes may become a useful and inexpensive approach to predict micro-BDTT before surgery. Furthermore, it can provide guidance for choosing a more suitable therapeutic strategies for patients.
There is undoubtedly that our investigation has some limitations. First, selection bias could have been present due to HCC patients without micro-BDTT was based on data from a single center and it does not include all of HCC patients without micro-BDTT from multicenters. Second, the number of patients with micro-BDTT was fairly small. However, because of low incidence of micro-BDTT, the number of cases is difficult to increase. We had already collected HCC patients with micro-BDTT from four centers. Only 46 with micro-BDTT were included in our study. Third, since this study was a retrospective study, C-reactive protein (CRP) was not routinely measured during the study period. Nevertheless, CRP was detected in only 21 (5.02%) patients in our study. more researches are warranted concerning the relationship between the micro-BDTT and CRP. In addition, it was very necessary to improve the nomogram with more factors. Some specific markers including some stem cell markers and small molecule metabolite biomarkers may also work as good non-invasive biomarkers for predicting HCC with micro-BDTT. Fourth, further external validation is needed to confirm the reliability of our predictive model through an independent and larger dataset. To our knowledge, this is the first study to construct a predictive nomogram including pre-treatment risk factors for predicting HCC patient with micro-BDTT, but there are still many deficiencies. Hence, further large-scale, prospective and multicentre studies are needed to confirm the results.