Preoperative prognostic nutritional index predicts both short and long-term outcomes after liver resection for hepatocellular carcinoma.

Background The aim of this study was to investigate the prognostic significance of the prognostic nutritional index (PNI) for both short and long term outcomes after liver resection for hepatocellular carcinoma (HCC). Methods 162 (without any previous treatment) of 229 surgically treated HCC patients were retrospectively analyzed. The cut off value of the preoperative PNI was 45.0. Patients were divided into two groups, PNI low (n=76) and high (n=86) group. Results Among some immune parameters such as PNI, neutrophil to lymphocyte ratio (NLR) and aspartate aminotransferase (AST) to lymphocyte ratio (ALRI), PNI had most reliable parameters in terms with prediction of both short and long term outcomes. Preoperative PNI tended to correlate with low skeletal muscle mass (SMM). In short term outcomes, PNI low group were more likely to have postoperative complications. The disease-free survival rate in PNI low group was significantly worse than that in the PNI high group (20.5 vs. 48.7 %, 5 year SR, p=0.03). On multivariate analysis, Low PNI was an independent prognostic factor for disease free survival (HR 1.65, p= 0.04). Conclusions The preoperative PNI was the most significant prognostic factor for evaluating both short and long-term outcomes after liver resection for HCC. therapy of HCC. In the present study, NLR was good biomarkers for predicting long-term outcomes after Hx. The molecular mechanism of an elevated NLR involved many


Abstract
Background The aim of this study was to investigate the prognostic significance of the prognostic nutritional index (PNI) for both short and long term outcomes after liver resection for hepatocellular carcinoma (HCC). Methods 162 (without any previous treatment) of 229 surgically treated HCC patients were retrospectively analyzed. The cut off value of the preoperative PNI was 45.0. Patients were divided into two groups, PNI low (n=76) and high (n=86) group. Results Among some immune parameters such as PNI, neutrophil to lymphocyte ratio (NLR) and aspartate aminotransferase (AST) to lymphocyte ratio (ALRI), PNI had most reliable parameters in terms with prediction of both short and long term outcomes. Preoperative PNI tended to correlate with low skeletal muscle mass (SMM).
In short term outcomes, PNI low group were more likely to have postoperative complications. The disease-free survival rate in PNI low group was significantly worse than that in the PNI high group (20.5 vs. 48.7 %, 5 year SR, p=0.03). On multivariate analysis, Low PNI was an independent prognostic factor for disease free survival (HR 1.65, p= 0.04). Conclusions The preoperative PNI was the most significant prognostic factor for evaluating both short and long-term outcomes after liver resection for HCC.

Background
In liver resection (Hx) for hepatocellular carcinoma (HCC), the perioperative complications and mortality has been improved recent years, however, it has been critical to manage patients with various comorbidity. Furthermore, the recurrent rate after curative Hx for HCC is still higher than other digestive organ cancers and it has been also important to acsses risk factors for recurrence after curative Hx. PNI (Prognostic nutritional index) was firstly reported in 1980 by Buzby et al. 1) in order to predict perioperative risk. However, calculation method was too complicated using many parameters such as serum albumin (Alb), triceps skinfold (TSF), transferrin (TFN) and delayed hypersensitivity skin testing (DHS). 4 years later, Japanese Onodera et al. 2) reported simpler modified PNI using serum Alb and total lymphocytes count (TLC) alone, and that Onodera's PNI has been widely used for perioperative risk assessment. In addition to perioperative risk prediction, PNI was also reported that it correlated with long-term prognosis of various cancers after curative treatment such as lung 3) , ovarian 4) , cervical 5) , gastric 6) and colorectal 7) cancers and so on.
In Hx for HCC, preoperative PNI was already reported to correlate with liver function such as albuminbilirubin (ALBI) grade, and to predict short-term outcomes after Hx for HCC within the Milan criteria 8) .
Chan et al. 9) reported that preoperative PNI predicted long-term prognosis after Hx in only early BCLC stage HCC. There were no reports of preoperative PNI for predicting both short and long term outcomes in whole HCC stage.
In the present study, among various immune parameters such as PNI, neutrophil to lymphocyte ratio (NLR) and aspartate aminotransferase (AST) to lymphocyte ratio (ALRI), the most reliable parameter was examined. The aim of this study was to investigate the prognostic significance of the preoperative PNI for both short and long term outcomes after Hx for whole stage HCC patients.

Preoperative immune parameters
Blood samples were taken prior to Hx. The PNI was the sum of serum albumin and 0.005×lymphocyte count. The NLR was calculated by dividing neutrophil count by lymphocyte count. ALRI was calculated by dividing AST by lymphocyte count. The cutoff value of PNI, NLR and ALRI was 45, 2.3 and 30.8 calculated by receiver-operating characteristic (ROC) curve for predicting recurrence after Hx.

Follow-up after Hx
Monthly follow-up was conducted by assessment of tumor markers (AFP, DCP, and AFP-L3) and ultrasonography. Dynamic computed tomography (CT) scan and Gd-EOB-DTPA-enhanced magnetic resonance imaging (MRI) were conducted at 3 and 6 months post operation. We defined recurrence as the appearance of new lesions with radiological features typical of HCC, as confirmed by at least two imaging methods.

Statistical analysis
All statistical analysis was performed using SPSS Version 21.0 statistical software (SPSS, Chicago, IL).
A p-value of less than 0.05 was considered statistically significant. Relationships between PNI and the clinicopathological variables were analyzed using the chi-square test and Mann-Whitney U test.
Survival curves were calculated using the Kaplan-Meier method and compared with the log-rank test.  Table 1 showed the comparison in both short and long-term outcomes among PNI, NLR and ALRI. The PNI alone predicted short-term outcomes, and both the PNI and NLR were reliable parameters for predicting the long-term outcomes. In terms with prediction of both short and long-term outcomes, PNI was most reliable parameters among three parameters.

Correlation between preoperative PNI and the clinicopathological variables
Correlations between preoperative PNI values and clinicopathological variables are shown in Table 2.
Low PNI significantly correlated with high age, or impaired liver function such as higher AST, higher ICGR15 and lower platelet levels. In tumor factors, low PNI tended to correlate with the only presence of microscopic vp alone. Furthermore, low PNI significantly correlated with lower SMM, which was called Sarcopenia.

Preoperative PNI and short-term outcomes
There were no significant differences in operative procedures between PNI low and high groups. Blood loss was significant much more in Low PNI group. Low PNI group tended to have more frequent severe postoperative complications, and had significant longer hospital stays after Hx (Table 3).

Preoperative PNI and long-term outcomes
In overall survival (OS), Low PNI group tended to have worse prognosis ( Figure 1A). In disease free survival (DFS), Low PNI group had significant worse prognosis than high PNI group ( Figure 1B). In univariate analysis for DFS, high AFP, high DCP, multiple tumors, the presence of microvascular invasion, more advanced stage and low PNI were selected for poor prognostic factors. In multivariate analysis revealed that high AFP, multiple tumors and low PNI were independent prognostic factors for DFS (Table 4). Regarding recurrent patterns, there was no significant difference between PNI low and high group (Figure 2).

Discussion
In the present study, some immune parameters including PNI, NLR and ALR were compared in terms with both short and long term outcome, and PNI was the most reliable parameters. In addition to the prediction of outcomes after HX, PNI significantly correlated with low SMM, Sarcopenia. This is the first reports of preoperative PNI for predicting both short and long term outcomes in whole HCC stage.
First of all, there were several reports about NLR for prognostic factors in HCC after curative treatment. He et al. 10) reported the usefulness of NLR and platelets to lymphocytes ratio (PLR) after transarterial chemoembolization. Taussig et al. also reported 11) that NLR predicted disease progression following intra-arterial therapy of HCC. In the present study, NLR was good biomarkers for predicting long-term outcomes after Hx. The molecular mechanism of an elevated NLR involved many factors and it remains poorly understood. However, a close relationship between the accumulation of tumor-associated macrophages in HCC and high NLR values has been observed in patients with HCC who underwent hepatic resection and living-donor liver transplantation 12) . A high NLR was also associated with a high infiltration of tumor-associated macrophages and high inflammatory cytokine production in the tumor, such as interleukin-6, interleukin-8 and interleukin-17, which promote systemic neutrophilia 13), 14) .
On the other hand, NLR was not correlated with short-term outcomes in the present study. PNI was only predictors for postoperative complications and hospital stays. PNI value, a combination of the albumin and total lymphocyte count, was parameters to evaluate the immunological and nutritional aspects of patients undergoing surgery. Ke et al. 15) reported that PNI was constructed as a reflection of a patient's nutritional status and it made sense that the PNI might be related to postoperative complications. The PNI included the lymphocyte count in its calculation. It has been found that the level of serum Alb and the count of lymphocyte had a tight relationship with the induction of the inflammatory response 16) . Therefore, it not only reflected the status of nutrition but also systemic inflammation.
For patients with a low PNI, it was essential to improve their outcomes through perioperative nutritional interventions, for example, the administration of branched-chain amino acid-enriched nutrient support 17), 18) . In the present study, PNI significantly correlated with Sarcopenia, so further nutritional intervention might be necessary for patients with a low PNI.

Conclusions:
Low PNI correlated with Sarcopenia reflecting low nutritional and inflammatory response.
Furthermore, preoperative PNI, rather than NLR and ALRI was the most significant and reliable prognostic factor for evaluating both short and long-term outcomes after Hx for HCC. Some nutritional interventions might be necessary for the patients with a low PNI.

Abbreviations
Prognostic nutritional index; PNI

Availability of data and materials
The current datasets are either deposited in publicly available repositories (where available and appropriate).

Competing interests
All authors declare that they have no competing interests.

Funding
All authors declare that they have no sources of funding for the research.    Figure 1 Long-term survival A. Overall survival Low PNI group tended to have worse prognosis (p=0.06). B. Disease free survival Low PNI group had significant worse prognosis than high PNI group (20.5 vs.

Figure 2
Recurrence patterns There was no significant difference in recurrent patterns.