Robotic-assisted radical resection versus open surgery for cholangiocarcinoma: a systematic review and meta-analysis.

To compare the clinical efficacy and safety of robot-assisted resection and open surgery for cholangiocarcinoma (CCA). We conducted a comprehensive search of PubMed, the Cochrane Library, and Embase databases for studies comparing treatment for CCA, covering the period from database inception to January 30, 2024. Two researchers will independently screen literature and extract data, followed by meta-analysis using Review Manager 5.3 software. A total of 5 articles with 513 patients were finally included. Among them, 231 in the robotic group, and 282 in the open group. The Meta-analysis revealed that the robotic group had a significant advantage in terms of intraoperative blood loss (MD = - 101.44, 95% CI - 135.73 to - 67.15, P < 0.05), lymph node harvest(MD = 1.03, 95% CI 0.30- 1.76, P < 0.05) and length of hospital stay(MD = - 1.92, 95% CI - 2.87 to- 0.97, P < 0.05). However, there were no statistically significant differences between the two groups in terms of transfusion rate (OR = 0.62, 95% CI 0.31-1.23, P > 0.05), R0 resection (OR = 1.49, 95% CI 0.89- 2.50, P > 0.05), 30-day mortality (OR = 1.68, 95% CI 0.43-6.65, P > 0.05) and complications (OR = 0.76, 95% CI 0.30- 1.95, P > 0.05). Robotic-assisted radical resection for CCA is feasible and safe, and its long-term efficacy and oncological outcomes need to be confirmed by further studies.

Contemporary trends and outcomes after liver transplantation and resection for intrahepatic cholangiocarcinoma.

BACKGROUND: Liver transplantation (LT) has been shown to be superior to resection in highly selected patients with perihilar cholangiocarcinoma (CCA), yet has traditionally been contraindicated for intrahepatic CCA (iCCA). Herein, we aimed to examine contemporary trends and outcomes for surgical resection and LT for iCCA. METHODS: The National Cancer Database was queried for patients presenting with stage I-III iCCA between 2010 and 2018 who underwent resection or LT. Overall survival (OS) was compared with Kaplan-Meier and multivariable Cox proportional hazards methods stratified by management. Secondary analysis of patients undergoing transplant for CCA was performed with the United Network for Organ Sharing database. RESULTS: Of 2565 patients, 2412 (94.0%) underwent resection and 153 (5.96%) LT of whom 84 (54.9%) received neoadjuvant therapy. Utilization of LT remained between 3.9% and 7.8% annually. Unadjusted 5-year OS was higher for LT than resection (59.8% vs 39.9%, P = .0067), yet adjusted analysis revealed no significant difference in mortality (hazard ratio, 0.91; 95% CI, 0.66-1.27; P = .58). On secondary analysis including 437 patients with all subtypes of CCA, unadjusted 5-year OS was higher for non-CCA indications (79% vs 52%-54%, P < .001). CONCLUSION: Utilization of LT for iCCA remains low and many cases are likely incidental. Although partial hepatectomy remains the standard of care for patients with resectable disease, our findings suggest that highly selected patients with unresectable iCCA may achieve favorable outcomes after LT. Granular, prospective data are needed to identify patients most likely to benefit from transplant and allocate scarce liver grafts.

Current State of Liver Transplantation for Cholangiocarcinoma: A Comprehensive Literature Review.

Cholangiocarcinoma is the second most common primary hepatic neoplasm, accounting for 10% to 20% of primary liver tumors and 3% of all gastrointestinal neoplasms. The 3 anatomic types (intrahepatic, perihilar, and distal) have distinct epidemiologies, etiopathogenesis, and clinical outcomes. Surgical resection remains the current standard of treatment, but outcomes remain poor. With the continued expansion of liver transplant programs, use of liver transplant for malignant indications has also increased, with reports of encouraging outcomes. However, given the scarcity of livers fortransplant and accompanying possible complications, liver transplant for treatment of patients with cholangiocarcinomas remains experimental in most of the world. We reviewed the existing literature on treatment modalities for cholangiocarcinoma with emphasis on the pros and cons of surgical resection and indications, protocols, and outcomes of liver transplant as a treatment modality for patients with cholangiocarcinoma.

[A Case of Hilar Cholangiocarcinoma Arising during Long-Term Follow-Up of Hepatolithiasis].

A 91-year-old man had a history of cholecystectomy and choledochostomy for cholecystolithiasis and choledocholithiasis. Eleven years earlier, intrahepatic stones were found in the posterior bile duct, and he did not wish to undergo treatment. Over time, worsening of the intrahepatic stones and dilation of the intrahepatic bile duct were observed. At 91 years old, enhanced abdominal CT revealed wall thickening of the hilar bile duct, and MRCP showed stenosis of the hilar bile duct. Endoscopic retrograde cholangiography showed no contrast in the right intrahepatic bile duct and marked dilation of the left intrahepatic bile duct. Brush cytology confirmed adenocarcinoma, leading to a diagnosis of hilar cholangiocarcinoma. He underwent open right and caudal lobectomy with biliary reconstruction. Histopathological examination revealed a hilar cholangiocarcinoma, T3N1M0, Stage Ⅲc, mainly located at the confluence of the right and left hepatic ducts. This case suggests a potential association between hepatolithiasis and hilar cholangiocarcinoma, emphasizing the importance of regular imaging examinations for timely surgical resection. Early intervention, including liver resection, is recommended for the management of hepatolithiasis.

Clinical implications of pediatric biliary intraepithelial neoplasia diagnosed from a choledochal cyst specimen.

BACKGROUND: Biliary intraepithelial neoplasia (BilIN), a noninvasive precursor of cholangiocarcinoma, can manifest malignant transformation. Since cholangiocarcinoma (CCA) may progress due to chronic inflammation in the bile ducts and gallbladder, choledochal cysts are considered a precursor to CCA. However, BilIN has rarely been reported in children, to date. METHODS: We reviewed medical records of patients (< 18 years of age, n = 329) who underwent choledochal cyst excision at Asan Medical Center from 2008 to 2022. BilIN was diagnosed in 15 patients. Subsequent analyses were performed of the demographics, surgical procedures, clinical course, and outcomes in these patients. Subgroup analysis and multivariate logistic regression test were performed to identify factors influencing BilIN occurrence. RESULTS: The mean age of the patients included in our study was 40.1 ± 47.6 months. In 15 patients, BilIN of various grades was diagnosed. Todani type I was prevalent in 80% of the patients. The median age at surgery was 17 months. During a mean follow-up of 63.3 ± 94.0 months, no adverse events such as stone formation in the remnant intrapancreatic common bile duct and intrahepatic duct or cholangiocarcinoma were observed, indicating a favorable outcome until now. CONCLUSIONS: The potential progression of choledochal cysts to BilIN in children was demonstrated. These results could underscore the importance of early and comprehensive excision of choledochal cysts, including resection margins for associated lesions and more thorough postoperative surveillance in patients with or at risk of BilIN.

Prognostic Impact of Visceral Adipose Tissue Imaging Parameters in Patients with Cholangiocarcinoma after Surgical Resection.

Visceral adiposity is known to be related to poor prognosis in patients with cholangiocarcinoma; however, the prognostic significance of the qualitative features of adipose tissue in cholangiocarcinoma has yet to be well defined. This study investigated the prognostic impact of adipose tissue imaging parameters reflecting the quantity and qualitative characteristics of subcutaneous (SAT) and visceral (VAT) adipose tissue on recurrence-free survival (RFS) and overall survival (OS) in 94 patients undergoing resection of cholangiocarcinoma. The area, mean computed tomography (CT) attenuation, and mean 2-deoxy-2-[18F]fluoro-D-glucose (FDG) uptake of SAT and VAT on positron emission tomography (PET)/CT for staging work-up were measured, and the relationship of these adipose tissue imaging parameters with clinicopathological factors and survival was assessed. TNM stage, histologic grade, lymphovascular invasion, and the size of cholangiocarcinoma showed positive correlations with adipose tissue imaging parameters. Multivariate survival analysis demonstrated that the visceral-to-subcutaneous adipose tissue area ratio (VSR) (p = 0.024; hazard ratio, 1.718) and mean FDG uptake of VAT (p = 0.033; hazard ratio, 9.781) were significant predictors for RFS, but all of the adipose tissue imaging parameters failed to show statistical significance for predicting OS. In addition to visceral adiposity, FDG uptake of VAT might be a promising prognostic parameter for predicting RFS in patients with cholangiocarcinoma.

An assessment of risk factors for recurrence and survival for patients undergoing liver resection for intrahepatic cholangiocarcinoma.

BACKGROUND AND AIMS: Intrahepatic cholangiocarcinoma (iCCA) is the second most common primary liver malignancy with increasing rates of incidence and mortality. Surgical resection is curative for patients who are diagnosed at early stages of iCCA. Limited data exist regarding risk factors for postresection recurrence and overall survival as iCCA is rare, and majority of patients are diagnosed at an advanced stage and thus not candidates for resection. We aimed to analyze clinical and laboratory characteristics, tumor histology, locoregional invasion, recurrence and survival in patients undergoing curative resection for iCCA. METHODS: All patients who underwent curative resection for iCCA between 2006 and 2023 at our institution were included in the study. Clinical characteristics, laboratory, histological and follow-up data were collected. RESULTS: The 1-, 3-, and, 5-year survival rates were 90.9%, 65.9% and 44.2%, respectively. About 65.6% of patients had recurrence in a median of 1.2 years after liver resection. Positive surgical margins were present in 20.73% of patients. Notably, 80.51% had solitary tumor and the remaining 19.48% had multifocal tumor. A total of 64.51% of patients received adjuvant chemotherapy after resection. A total of 26 (31.3%) patients had died during the follow-up period. Duration from liver resection to last follow-up or death was 1.6 years (0.8-3.2). Overall median survival was 4.6 years. The presence of lymph node metastases, vascular invasion, positive surgical margin and advanced tumor stage at diagnosis were associated with significantly worse overall survival, which remained significant in multivariable model for advanced tumor stage and positive surgical margin. CONCLUSION: Despite curative resection, recurrence rate is high and overall survival is poor in patients with iCCA. Real-world data regarding patient characteristics and longitudinal follow-up remain important as iCCA is a rare malignancy.

Current considerations on intraductal papillary neoplasms of the bile duct and pancreatic duct.

Pancreatobiliary intraductal papillary neoplasms (IPNs) represent precursors of pancreatic cancer or bile duct cholangiocarcinoma that can be detected and treated. Despite advances in diagnostic methods, identifying these premalignant lesions is still challenging for treatment providers. Modern imaging, biomarkers and molecular tests for genomic alterations can be used for diagnosis and follow-up. Surgical intervention in combination with new chemotherapeutic agents is considered the optimal treatment for malignant cases. The balance between the risk of malignancy and any risk of resection guides management policy; therefore, treatment should be individualized based on a meticulous preoperative assessment of high-risk stigmata. IPN of the bile duct is more aggressive; thus, early diagnosis and surgery are crucial. The conservative management of low-risk pancreatic branch-duct lesions is safe and effective.

Robotic Versus Open Hepatic Arterial Infusion Pump Placement for Unresectable Intrahepatic Cholangiocarcinoma.

BACKGROUND: Hepatic arterial infusion pump (HAIP) chemotherapy is an effective treatment for patients with unresectable intrahepatic cholangiocarcinoma (iCCA). HAIP chemotherapy requires a catheter inserted in the gastroduodenal artery and a subcutaneous pump. The catheter can be placed using an open or robotic approach. OBJECTIVE: This study aimed to compare perioperative outcomes of robotic versus open HAIP placement in patients with unresectable iCCA. METHODS: We analyzed patients with unresectable iCCA included in the PUMP-II trial from January 2020 to September 2022 undergoing robotic or open HAIP placement at Amsterdam UMC, Erasmus MC, and UMC Utrecht. The primary outcome was time to functional recovery (TTFR). RESULTS: In total, 22 robotic and 28 open HAIP placements were performed. The median TTFR was 2 days after robotic placement versus 5 days after open HAIP placement (p < 0.001). One patient (4.5%) in the robotic group underwent a conversion to open because of a large bulky tumor leaning on the hilum immobilizing the liver. Postoperative complications were similar-36% (8/22) after robotic placement versus 39% (11/28) after open placement (p = 1.000). The median length of hospital stay was shorter in the robotic group-3 versus 5 days (p < 0.001). All 22 robotic patients initiated HAIP chemotherapy post-surgery, i.e. 93% (26/28) in the open group (p = 0.497). The median time to start HAIP chemotherapy was 14 versus 18 days (p = 0.153). CONCLUSION: Robotic HAIP placement in patients with unresectable iCCA is a safe and effective procedure and is associated with a significantly shorter TTFR and hospital stay than open HAIP placement.

Multimodal treatment with endoscopic ablation and systemic therapy for cholangiocarcinoma.

Cholangiocarcinoma (CCA) are primary malignancies of biliary system and usually unresectable at the time of diagnosis. As a consequence, majority of these cases are candidates for palliative care. With the advances in chemotherapeutic agents and multidisciplinary care, the survival rate has improved in cases with inoperable malignant biliary obstruction. As a consequence, there is a need to provide effective and durable palliative care in these patients. The main role of endoscopic palliation in the vast majority of CCA includes biliary stenting for obstructive jaundice. Recent advances in the endoscopic palliation and multimodal approach appear promising in imparting durable relief of symptoms. Use of radiofrequency ablation, photodynamic therapy and intraluminal brachytherapy has been shown to improve the survival rates as well as the patency of biliary stents. Infact, intraductal ablation may act synergistically with chemotherapy by modulating tumour signalling pathways and immune microenvironment.

Impact of sarcopenia on the short-term and long-term outcomes of intrahepatic cholangiocarcinoma undergoing hepatectomy: A multi-center study.

BACKGROUND: Sarcopenia is associated with adverse prognosis of intrahepatic cholangiocarcinoma (iCCA) after surgery. METHODS: 321 patients with iCCA undergoing surgery were retrospectively recruited and assigned to training and validation cohort. Skeletal muscle index (SMI) was assessed to define sarcopenia. Logistic regression and cox regression analysis were used to identify risk factors. A novel sarcopenia-based nomogram was constructed and validated by ROC curves, calibration curves, and DCA curves. RESULTS: 260 patients were included for analysis. The median age was 63.0 years and 161 patients (61.9%) were diagnosed with sarcopenia. Patients with sarcopenia exhibited a higher rate of postoperative complications, a worse OS and RFS than patients without sarcopenia. Sarcopenia, low albumin and intraoperative blood transfusion were independent risk factors of postoperative complications, while sarcopenia and low albumin were risk factors of high CCI≥26.2. Sarcopenia, high PS score, low-undifferentiated differentiation, perineural invasion, TNM stage III-IV were risk factors of OS, and a novel nomogram based on these five factors was built to predict the 12-, 24-, and 36-months OS, with the mean AUC > 0.6. CONCLUSION: Sarcopenia is negatively associated with both postoperative complications and survival prognosis of iCCA undergoing hepatectomy.

Prognostic Factors in Intrahepatic Cholangiocarcinoma - A Systematic Review.

Introduction: intrahepatic cholangiocarcinoma (ICCA) are rare, aggressive cancers that develop in second order or smaller bile ducts. The aim of this review is to systematically review the most important prognostic factors affecting the long-term outcomes of these patients. Material and Methods: articles conducted on this issue, written in English, published between from January 2000 to December 2023 in Cochrane Library, PubMed, Embase, MedLine, Web of Science, Elsevier, Google Scholar were systematically researched and reviewed. Results: ICCA are usually late diagnosed cancers because of the asymptomatic character, and curative procedures are often not feasible, only 20 to 30% of patients being fit for surgery. With the prognostic of this aggressive malignancy being baleful, the most important risk factors but also prognosis factors seem to be represented by socioeconomic factors, morphological presentation, dimensions, number and extension of the tumor as well as resection margins. Conclusions: once these factors are widely recognized and identified in each case, the clinician will be able to find the best treatment for these patients in order to improve the long-term outcomes.

The complication-overall survival (CompOS) risk tool predicts risk of a severe postoperative complications relative to long-term survival among patients with primary liver cancer.

BACKGROUND: This study aimed to develop a tool based on preoperative factors to predict the risk of perioperative complications based on the Comprehensive Complication Index (CCI) and long-term survival outcomes after liver resection for primary liver cancer. METHODS: Patients with hepatocellular carcinoma (HCC) or intrahepatic cholangiocarcinoma (ICC) undergoing curative-intent hepatectomy between 1990 and 2020 were identified using a multi-institutional international database. RESULTS: Among 1411 patients who underwent curative-intent hepatic resection (HCC: 997, 70.7%; ICC: 414, 29.3%), median patient age was 66.0 years (IQR, 57.0-73.0), and most patients were male (n = 1001, 70.9%). In the postoperative setting, 699 patients (49.5%) experienced a complication; moreover, 112 patients (7.9%) had major complications. Although most patients had a favorable risk complication-overall survival (CompOS) profile (CCI score > 40 risk of <30% and median survival of >5 years: n = 778, 55.1%), 553 patients (39.2%) had an intermediate-risk profile, and 80 patients (5.7%) had a very unfavorable risk profile (CCI score > 40 risk of ≥30% and/or median survival of ≤1.5 years). The areas under the curve of the test and validation cohorts were 0.73 and 0.76, respectively. CONCLUSION: The CompOS risk model accurately stratified patients relative to short- and long-term risks, identifying a subset of patients at a high risk of major complications and poor overall survival.

[Advancements and controversies in conversion therapy for biliary tract malignant tumors with insufficient future liver remnant].

Due to the unique location and aggressive tumor biology,hilar cholangiocarcinoma,intrahepatic cholangiocarcinoma,and gallbladder cancer often present with obstructive jaundice and require extensive liver resection,also exhibit high rates of recurrence and metastasis after radical excision. Therefore,surgeons should make treatment decisions based on the biliary anatomy of patients and the biological characteristics of tumors as it significantly affects patient's prognosis. Treatment strategy should be made to ensure the successful implementation of radical resection for biliary tract malignant tumors while maximizing the survival benefits of patients. Firstly,conversion of liver function by relieving jaundice technology and conversion of tumor biological characteristics through systematic therapy,followed by the conversion of future liver remnant. Currently,there are still controversies surrounding indications,methods,standards of relieving jaundice,and treatment plans,cycles,evaluation of therapeutic effects for systematic conversion therapy,and the standards and techniques of conversion therapy for future liver remnant.This article discusses these issues through literature analysis and the author's experience in the hope of resonating with colleagues.

[Surgical treatment and prognosis analysis of hilar cholangiocarcinoma].

Objective: To investigate the surgical treatment effect and prognostic factors of hilar cholangiocarcinoma. Methods: This is an ambispective cohort study. From August 2005 to December 2022,data of 510 patients who diagnosed with hilar cholangiocarcinoma and underwent surgical resection at the Hepatobiliary Center of the First Affiliated Hospital of Nanjing Medical University were retrospectively collected. In the cohort,there were 324 males and 186 females,with an age of (M (IQR)) 63(13)years (range:25 to 85 years). The liver function at admission was Child-Pugh A (343 cases,67.3%) and Child-Pugh B (167 cases,32.7%). Three hundred and seventy-two(72.9%) patients had jaundice symptoms and the median total bilirubin was 126.3(197.6) µmol/L(range: 5.4 to 722.8 µmol/L) at admission. Two hundred and fourty-seven cases (48.4%) were treated with percutaneous transhepatic cholangial drainage or endoscopic nasobiliary drainage before operation. The median bilirubin level in the drainage group decreased from 186.4 µmol/L to 85.5 µmol/L before operation. Multivariate Logistic regression was used to identify the influencing factors for R0 resection,and Cox regression was used to construct multivariate prediction models for overall survival(OS) and disease-free survival(DFS). Results: Among 510 patients who underwent surgical resection,Bismuth-Corlett type Ⅲ-Ⅳ patients accounted for 71.8%,among which 86.1% (315/366) underwent hemi-hepatectomy,while 81.9% (118/144) underwent extrahepatic biliary duct resection alone in Bismuch-Corlett type Ⅰ-Ⅱ patients. The median OS time was 22.8 months, and the OS rates at 1-,3-,5-and 10-year were 72.2%,35.6%,24.8% and 11.0%,respectively. The median DFS time was 15.2 months,and the DFS rates was 66.0%,32.4%,20.9% and 11.0%,respectively. The R0 resection rate was 64.5% (329/510), and the OS rates of patients with R0 resection at 1-,3-,5-and 10-year were 82.5%, 48.6%, 34.4%, 15.2%,respectively. The morbidity of Clavien-Dindo grade Ⅲ-Ⅴ complications was 26.1%(133/510) and the 30-day mortality was 4.3% (22/510). Multivariate Logistic regression indicated that Bismuth-Corlett type Ⅰ-Ⅲ (P=0.009), hemi-hepatectomy and extended resection (P=0.001),T1 and T2 patients without vascular invasion (T2 vs. T1:OR=1.43 (0.61-3.35),P=0.413;T3 vs. T1:OR=2.57 (1.03-6.41), P=0.010;T4 vs. T1, OR=3.77 (1.37-10.38), P<0.01) were more likely to obtain R0 resection. Preoperative bilirubin,Child-Pugh grade,tumor size,surgical margin,T stage,N stage,nerve infiltration and Edmondson grade were independent prognostic factors for OS and DFS of hilar cholangiocarcinoma patients without distant metastasis. Conclusions: Radical surgical resection is necessary to prolong the long-term survival of hilar cholangiocarcinoma patients. Hemi-hepatectomy and extended resection,regional lymph node dissection and combined vascular resection if necessary,can improve R0 resection rate.

[Prediction of prognosis of patients with radical resection of intrahepatic cholangiocarcinoma based on single cell omics].

Objectives: To analyze the survival benefit of intrahepatic cholangiocarcinoma (ICC) radical resection based on single cell omics. Methods: This is a retrospective case-series study. ICC single-cell sequencing was integrated from four data sets in the Gene Expression Omnibus Database, with a total of 46 patients undergoing radical resection, to explore the characteristics of the microenvironment. Microarray data of 100 ICC cases was analyzed in the EMBI database with survival data. The infiltration abundance of each epithelial cell cluster was calculated in each microarray data sample using the ssGSEA algorithm. The key epithelial cell cluster associated with poor patient outcomes was explored. The clinical value of key marker genes in this subgroup was studied. Prognostic marker genes were selected using the univariate and multivariate Cox proportional hazards(CoxPH) model. The The CoxPH model was constructed by the target genes and a nomogram was drawn. Kaplan-Meier survival analysis was used to verify the relationship between score and prognosis of patients. The predictive power of the model was evaluated by receiver operating characteristic(ROC) curves, calibration curves, and decision curve analysis (DCA). Results: Epithelial cell clusters infiltrated almost exclusively in tumor tissue. The MT2A+ epithelial cell subset was associated with a poorer prognosis for patients with a high invasion abundance and patients characterized by infiltration of this group were defined as antioxidant. After screening marker genes in this cluster using a univariate and multivariate CoxPH model, the following genes were found to be independent prognostic factors: FILPIL, NFKBIA, PEG10, SERPINB5. The CoxPH model was constructed using the four gene expression levels, and the survival rate of patients in the high-risk group was significantly lower than those in the low-risk group (all P<0.05). The constructed nomogram had good discrimination and validity. The ROC curve showed that the predicted area under the curve was 0.779, 0.844 and 0.845 at 1, 3 and 5 years, respectively. Compared to clinical indicators, the model had better predictive power using the calibration curve and the DCA test. Conclusions: The MT2A+ epithelial cell group may be associated with the prognosis of patients with ICC, and the concept of ICC tissue typing of antioxidant and non-antioxidant types is proposed. The type of antioxidant may predict the poor prognosis of the patients, and postoperative adjuvant therapy and other means could be considered to improve the survival of the patients.

Laparoscopic Tracer Technique for Liver Lymphatic Drainage by Injecting Indocyanine Green into the Glisson Pedicle.

BACKGROUND: Currently, an effective tracer technique for lymphatic drainage during laparoscopic surgery has not been established. This study aimed to elucidate a new fluorescence, imaging technique targeting the hepatic lymphatic drainage area, using indocyanine green (ICG). METHODS: A patient diagnosed with intrahepatic cholangiocarcinoma (ICC) located in segment 8 of the liver was injected with ICG into the connective tissue of the Glisson pedicle supplied by the lesion's liver segment, avoiding the bile duct, portal vein, and hepatic artery. This was performed under the guidance of laparoscopic ultrasonographic localization to trace the lymph nodes. RESULTS: The lymphatic drainage area traced intraoperatively by ICG was consistent with the definition of the right regional lymph nodes for ICC. The lymph nodes were dissected, followed by addition of a fluorescence tracer. CONCLUSIONS: Mastering intraoperative ultrasonic puncture technology can enable effective and accurate tracing of the lymph nodes of the liver segment where the lesion is located. However, the technical standards for this methodology need to be established through further studies.