Remnant liver function is associated with long-term survival in patients with hepatocellular carcinoma undergoing hepatectomy

It is important to assess the prognosis and intervene before and after surgery in patients with hepatocellular carcinoma. This study aims to elucidate the association of outcomes and residual liver function after hepatectomy. A total of 176 patients who underwent the initial resection for hepatocellular carcinoma between January 2011 and March 2021 at Jichi Medical University were included. Hepatic clearance of the remnant liver was measured using 99mTc-galactosyl serum albumin scintigraphy. The log-rank test was used to analyze survival using the Kaplan–Meier method. Hazard ratios (HR) and 95% confidence intervals (CI) for overall survival were calculated using Cox’s proportional hazard model. In multivariate analysis, microvascular invasion, intraoperative blood loss, and hepatic clearance of the remnant liver were independently associated with overall survival. Hepatic clearance of the remnant liver was independently associated with recurrence free survival. This is the first report to show that lower residual liver function is associated with shorter survival in patients with hepatocellular carcinoma undergoing hepatectomy. Preoperative determination of remnant liver function may allow assessment of prognosis in patients planned to undergo resection of hepatocellular carcinoma. Preservation of liver functional reserve may be crucial for improved long-term outcomes after hepatectomy.


Discussion
Many reports have demonstrated that residual liver function is associated with short-term outcomes, mainly post-hepatectomy liver failure, but no reports have discussed the impact of residual liver function on long-term outcomes.In the present study, independent prognostic factors significantly associated with overall survival were microvascular invasion, intraoperative blood loss and remnant liver function.The independent prognostic factor significantly associated with recurrence free survival was remnant liver function.The results of the present study show that measurement of remnant liver function may be useful to predict the overall and recurrence free survival in patients with hepatocellular carcinoma undergoing hepatectomy.Decreased intraoperative bleeding may result in improved survival.Owing to the high recurrence rate after hepatectomy, risk factors for tumor recurrence must be ascertained.That information could help be used to guide interventions earlier and facilitate better surveillance to reduce the rate of recurrence and improve the quality of care for patients with hepatocellular carcinoma.
There was not significant difference between insufficient hepatic clearance of remnant liver and both of tumor size (p = 0.3272) and microvascular invasion (p = 0.4177).Therefore advanced cancer situation may not be associated with insufficient hepatic clearance of the remnant liver.And insufficient hepatic clearance of the remnant liver was associated with tumor recurrence, therefore, insufficient hepatic clearance of the remnant liver itself may be driving prognostic risk.In the high clearance group, 32 patients (30%) underwent anatomical resection and in the low clearance group, 30 patients (42%) underwent anatomical resection (p = 0.1086).In our results, anatomical hepatic resections may not be associated with prolonged prognosis.Regardless of the surgical technique, the resulting remnant liver function may have an impact on prognosis.
Several methods of assessing residual liver function have been reported using computed tomography scan, magnetic resonance intensity, or GSA scintigraphy.Computed tomography scans clearly show the liver volume, but liver volume does not assess liver function.GSA scintigraphy and gadolinium ethoxybenzyldiethylenetriaminepentaacetic acid magnetic resonance intensity can quantitatively assess partial liver function and is useful for determining treatment intensity in patients with reduced hepatic reserve 8 .As a method to assess total liver function, the ICG test is the widely used throughout the world.ICG-R15 is reported to be an early indicator of hepatic dysfunction and has been used preoperatively to plan the extent of partial hepatectomy by predicting the risk of dysfunction after surgery.ICG-R15 together with γ-glutamyl transpeptidase was reported to be an independent preoperative factor associated with recurrence free survival 9 .However, because this method assumes the absence of interregional disparities of liver function, ICG-R15 cannot accurately predict residual liver function in the presence of interregional functional disparities due to impaired blood flow or biliary obstruction.Recently, the ALBI score has also been used as a prognostic factor.However, in the present study, the ALBI score is not associated with long-term outcomes in patients with hepatocellular carcinoma undergoing hepatectomy.In the present study, hepatic clearance of the remnant liver is associated with long-term outcomes.However, LHL15 expressing the whole liver function did not predict the long-term outcomes.Taken together, residual liver function may be more useful than total liver function in predicting long-term outcomes in patients with hepatocellular carcinoma undergoing hepatectomy.
A cut off value of < 205 ml/min clearance of the remnant liver was determined using the receiver operating characteristic curve method.The mean hepatic clearance of a normal liver is 400 ml/min ± 100 ml/min, so a clearance of 205 ml/min is approximately 2 standard deviations below the mean.This study shows that the prognosis of patients with a hepatic clearance of the remnant liver < 205 ml/min is poor.Further studies are needed to clarify the clinical significance of these values.
Massive hemorrhage remains a major complication of liver surgery.Increased blood loss during liver surgery has a significant impact on morbidity and mortality, and perioperative blood transfusions are associated with higher rates of postoperative complications and tumor recurrence 10,11 .Intraoperative blood loss was shown to result in immunosuppression by reducing natural killer cell activity and T-helper 1 lymphokines 12,13 .Many reports showed that blood transfusions negatively impact outcomes of hepatectomy.Devascularization techniques, hemostatic procedures, intraoperative ultrasound, and low central venous pressure inhalation have reduced intraoperative blood loss during hepatic resections [14][15][16] .Despite the availability of novel transection devices, vascular control is often required in complex hepatic procedures to avoid excessive bleeding 17 .Recently, laparoscopic hepatectomy has been introduced and has been shown to reduce blood loss, but increased longterm survival has not yet been reported 18,19 .The problem may not be due to the hemorrhage itself, but rather to a decrease in liver function due to liver damage caused by hemorrhage and ischemic-reperfusion injury, which may affect the liver function and prognosis.Therapeutic strategies tackling ischemic-reperfusion injury could not only improve post-surgical organ function, but also may reduce the risk of tumor recurrence 20 .
Microvascular invasion, reported in 15-57.1% surgical specimens of hepatocellular carcinoma 21 , is associated with aggressive biological features of hepatocellular carcinoma, which has been established as a risk factor for early recurrence and poor outcomes 22 .The exact biological mechanisms accounting for enhanced oncologic risk observed are not yet clear.Release of cancer cells by surgical manipulation with subsequent hematogenous spread could be one important means of metastasis formation 23 .To improve the prognosis of patients with hepatocellular carcinoma with microvascular invasion, anatomical subsegmentectomy or partial hepatectomy with a wide resection margin is recommended.In the present study, low hepatic clearance of the remnant liver was associated with shorter overall and recurrence free survival.Further study is needed to decide the optimal surgical margins.www.nature.com/scientificreports/Hepatocellular carcinoma patients with vascular invasion and cirrhosis have a high rate (78-83%) of developing recurrent disease within 6-35 months after resection 24 .In this study, the ratio that remnant liver clearance divided by total liver clearance was associated with micro vascular invasion (p = 0.0248) and tumor size (p = 0.0423).The ratio that remnant liver clearance divided by total liver clearance was associated with pathological findings and the remnant liver clearance.Therefore, the function of the remnant liver clearance may be associated with the recurrence of the primary tumor.The mechanism of the recurrence of the primary tumor is unclear.The possible explanation is that cirrhosis is associated with cytochrome p450 mediated drug clearance 25 .The down-regulation of the CYP2C19 gene were associated with the recurrence free survival in hepatocellular carcinoma 26 .CYP gene may be associated with the recurrence of the primary tumor.Further investigation is necessary to clarify the mechanism of the recurrence of primary tumor.
This study has several limitations.This is a retrospective study conducted at a single center with a relatively small sample size.If we use the value in clinical setting, we need another validation cohort.In this cohort, we do not have enough patient to validate.We need the further study to validate it in prospective multicenter trial.Potential confounding factors were assessed using descriptive statistics and univariable analysis and these factors were adjusted for whenever possible.Preoperative GSA scintigraphy was routinely performed to estimate total liver function.LHL15, remnant liver function, and laboratory data were objectively assessed in advance, which limited the risk of observation bias.The results presented should be prospectively validated in a larger population at multiple centers.

Conclusion
To the best of our knowledge, this is the first report to show that low residual liver function is associated with shorter survival in patients with hepatocellular carcinoma undergoing hepatectomy.Preoperative measurement of remnant liver function may assist predicting prognosis in patients with hepatocellular carcinoma.Preservation of liver functional reserve may be crucial for improved long-term outcomes after hepatectomy in patient with hepatocellular carcinoma.

Patients and methods
Patients.A total of 176 patients who underwent the initial resection of hepatocellular carcinoma between January 2011 and March 2021 at Jichi Medical University were included in this study.There are no patients who died within 1 month after hepatectomy.All patients were regularly screened for recurrence using serum alphafetoprotein levels, protein induced by vitamin K absence II, and dynamic computed tomography (CT) scan every 3 months.The protocol for this study was approved by the Institutional Review Board and conforms to the provisions of the Declaration of Helsinki.All methods were carried out in accordance with relevant guidelines and regulations.
Blood samples obtained preoperatively were analyzed for routine liver tests.The cut-off values for intraoperative blood loss, hepatic clearance of the remnant liver, and liver to heart-plus-liver radioactivity at 15 min (LHL15) were determined by using a receiver operating characteristic curve analysis of overall survival (OS).The cut-off values for aspartate aminotransferase, alanine transaminase, γ-glutamyl transpeptidase, alpha-fetoprotein, and protein induced by vitamin K absence II were determined using hospital reference values.Recurrence was confirmed as local or distant by CT scan findings.For patients with recurrence, treatment was selected based on the performance status of the patient, liver function and extent of the recurrent tumors.OS was defined from the date of surgery to the date of death or last contact with the patient (censored).Recurrence-free survival was defined from the date of liver resection to the first recurrence at any site.Recurrence-free survival data were censored for patients who were alive without recurrence at the last follow-up date or who died without tumor recurrence.The tumor staging of patients with hepatocellular carcinoma followed the 8th edition of the American Joint Committee on Cancer staging system.The procedures for hepatectomy were categorized according to the Brisbane Nomenclature from the International Hepato-Pancreato-Biliary Association 27 .Briefly, the anatomic resection was defined as resection of the tumor together with the related portal vein branches and the corresponding hepatic territory.Major surgery was defined as hemihepatectomy and extended hemihepatectomy.
Estimation of function of the remnant liver using GSA SPECT image.Patients underwent preoperative GSA scintigraphy as previously reported using a dual-head rotating gamma camera system and a dedicated data processing unit (Prism Axis, Picker Prism International, Cleveland, OH).A single bolus of 3 mg GSA (185 MBq; Nihon Medi-Phisics, Nishinomiya, Japan) was injected intravenously.After confirmation that the detector covered the area of the liver and heart, acquisition of planar images was begun with an acquisition time of 15 s each for 16 min immediately after injection.After acquisition of planar images, dynamic single photon emission tomography (SPECT) acquisition was started with an acquisition time of 20 s every 5 min.To generate a set of images equivalent to static SPECT images, projection data from dynamic SPECT were merged.Total liver function was calculated as the total liver GSA clearance, expressed in ml/min by the Patlak plot method.Regions of interest were generated for the entire liver on tomographic images using iso-count methods (25% cutoff of minimal count) to estimate the liver functional volume (ml).Hepatic clearance and functional volume of the remnant liver were estimated from fusion with CT scan images.Briefly, images from the CT scan were aligned with the image of the liver SPECT image with reference to the hepatic vein on every 3-mm liver cross-slice as a landmark on contrast-enhanced helical CT scan images.After the transection line had been set on the SPECT images based on the surgical procedure, the remnant liver with the resection line was determined manually.Remnant liver function was calculated from the proportional allocation of voxel count in static SPECT by the Patlak plot method and expressed by GSA clearance (ml/min).Regional functional liver volume (ml) was also calculated from the SPECT data by the outline extraction method.

Figure 2 .
Figure 2.Kaplan-Meier curves for overall and recurrence-free survival associated with hepatic clearance of the remnant liver.(a) Overall survival comparing patients with hepatic clearance of the remnant liver < 205 ml/ min and hepatic clearance of the remnant liver ≥ 205 ml/min.The overall survival in those with a hepatic clearance of the remnant liver ≥ 205 ml/min was significantly longer than that of those with clearance < 205 ml/ min (p = 0.0033).(b) Recurrence free survival comparing patients with hepatic clearance of the remnant liver < 205 ml/min and hepatic clearance of the remnant liver ≥ 205 ml/min.The recurrence free survival of those with a hepatic clearance of the remnant liver ≥ 205 ml/min was significantly longer than that those with clearance < 205 ml/min (p = 0.0095). https://doi.org/10.1038/s41598-023-42929-x

Table 1 .
Patient characteristics according to hepatic clearance of the remnant liver.AFP alpha fetoprotein, PIVKA II protein induced by vitamin K absence, ALBI albumin bilirubin, LHL15 liver to heart-plus-liver radioactivity at 15 min, *P < 0.05.

Table 2 .
Analysis of factors associated with overall survival.HR hazard ratio, CI confidence interval, AFP alpha fetoprotein, PIVKA II protein induced by vitamin K absence, ALBI albumin bilirubin, LHL15 liver to heart-plus-liver radioactivity at 15 min, *P < 0.05.

Table 3 .
Analysis of factors associated with recurrence free survival.HR hazard ratio, CI confidence interval, AFP alpha fetoprotein, PIVKA II protein induced by vitamin K absence, ALBI albumin bilirubin, LHL15 liver to heart-plus-liver radioactivity at 15 min.*P < 0.05.