Are there any benefits of prolonged hypothermic oxygenated perfusion? - Results from a national retrospective study.

BACKGROUND: Dual hypothermic oxygenated perfusion (DHOPE) is increasingly being used to extend liver preservation to improve transplant logistics. However, little is known about its benefits in high-risk liver grafts. This study aimed to investigate whether prolonged DHOPE provides benefits other than improved logistics in all liver types. METHODS: We performed a national retrospective cohort study of 177 liver transplants from 12 Italian centers preserved with DHOPE for ≥4h between 2015 and 2022. A control group of 177 DHOPEs of <4h during the same period was created using 1:1 propensity score matching. The impact of risk profiles and preservation times on the outcomes was assessed using univariable and multivariable regression models. RESULTS: No significant differences in post-transplant outcomes were found between prolonged and short DHOPEs. However, the prolonged group had a significantly lower incidence of post-transplant acute kidney injury (AKI) compared to the short group (30.5% vs. 44.6%, p=0.008). Among prolonged DHOPEs, no differences in transplant outcomes were observed according to donor risk index (DRI), Eurotransplant definition for marginal grafts, and balance of risk (BAR) score. DHOPE duration was associated with a lower risk of AKI in multivariable models adjusted for DRI, Eutrotransplant marginal grafts, and BAR score. Prolonged HOPE confirmed its protective effect against AKI in a multivariable model adjusted for donor and recipient risk factors [OR: 0.412, 95%CI: 0.200-0.850, p=0.016]. CONCLUSIONS: Prolonged DHOPE is widely used to improve transplant logistics, provides good results with high-risk grafts, and appears to be associated with a lower risk of post-transplant AKI. These results provide further insight into the important role of DHOPE in preventing post-transplant complications.

Assessment of liver graft quality during hypothermic oxygenated perfusion: the first international validation study.

BACKGROUND AND AIM: While it is currently assumed that liver assessment is only possible during normothermic machine perfusion (NMP), there is uncertainty regarding a reliable and quick prediction of graft injury during ex situ hypothermic oxygenated perfusion (HOPE). We therefore intended to test, in an international liver transplant cohort, recently described mitochondrial injury biomarkers measured during HOPE before liver transplantation. STUDY DESIGN: Perfusate samples of human livers from 10 centers in 7 countries with HOPE-experience were analyzed for released mitochondrial compounds, i.e. flavin mononucleotide (FMN), NADH, purine derivates and inflammatory markers. Perfusate FMN was correlated with graft loss due to primary non-function or symptomatic non-anastomotic biliary strictures (NAS), and kidney failure, as well as liver injury after transplantation. Livers deemed unsuitable for transplantation served as negative control. RESULTS: We collected 473 perfusate samples of human DCD (n=315) and DBD livers (n=158). Fluorometric assessment of FMN in perfusate was validated by mass spectrometry (R=0.7011,p<0.0001). Graft loss due to primary non-function or cholangiopathy was predicted by perfusate FMN values (c-statistic mass spectrometry 0.8418 (95%CI 0.7466-0.9370,p<0.0001), c-statistic fluorometry 0.7733 (95%CI 0.7006-0.8461,p<0.0001). Perfusate FMN values were also significantly correlated with symptomatic NAS and kidney failure, and superior in prediction of graft loss when compared to conventional scores derived from donor and recipient parameters, such as the donor risk index and the balance of risk score. Mitochondrial FMN values in liver tissues of non-utilized livers were low, and inversely correlated to high perfusate FMN values and purine metabolite release. CONCLUSIONS: This first international study validates the predictive value of the mitochondrial co-factor FMN, released from complex I during HOPE, and may therefore contribute to a better risk stratification of injured livers before implantation. IMPACT AND IMPLICATIONS: Analysis of 473 perfusates, collected from 10 international centers during hypothermic oxygenated perfusion (HOPE), revealed that mitochondria derived flavin mononucleotide (FMN) values in perfusate is predictive for graft loss, cholangiopathy, and kidney failure after liver transplantation. This result is of high clinical relevance, as recognition of graft quality is urgently needed to improve the safe utilization of marginal livers. Ex-situ machine perfusion approaches, such as HOPE, are therefore likely to increase the number of useable liver grafts.

Utility of circulating tumor DNA in secondary liver malignancies: What we know and what is to come.

Secondary liver malignancies are a serious and challenging global health concern. Secondary metastasis to the liver is most commonly from colorectal cancer that has metastatically spread through splanchnic circulation. Metastatic diseases can portend poor prognosis due to the progressive nature typically found on detection. Improvements in detection of disease, monitoring therapy response, and monitoring for recurrence are crucial to the improvement in the management of secondary liver malignancies. Assessment of ctDNA in these patient populations poses an opportunity to impact the management of secondary liver malignancies. In this review, we aim to discuss ctDNA, the current literature, and future directions of this technology within secondary liver malignancies.

Circulating tumor DNA in management of primary liver malignancy: A review of the literature and future directions.

Primary liver malignancies are a serious and challenging global health concern. The most common primary tumors are hepatocellular carcinoma and cholangiocarcinoma. These diseases portend poor prognosis when presenting with progressive, extensive disease. There is a critical need for improved diagnosis, therapeutic intervention, and monitoring surveillance in liver-related malignancies. Liquid biopsy using ctDNA provides an opportunity for growth within these domains for liver-related malignancy. However, ctDNA is relatively understudied in this field compared with other solid tumor types, possibly due to the complex nature of the pathology. In this review, we aim to discuss ctDNA, the current literature, and future directions of this technology within primary liver malignancies.

Disease progression of side-branch intraductal papillary mucinous neoplasms following solid organ transplant.

BACKGROUND: Branch-duct intraductal papillary mucinous neoplasms (BD-IPMNs) are becoming more prevalent with advanced medical imaging and account for most of pancreatic cystic neoplasms (PCNs). Most incidental lesions should be surveyed, with resection reserved for specific, high-risk cases. Solid organ transplantation candidates may be high risk of resection before transplant and will require systemic immunosuppression after transplant, which has been theorized to alter the natural history of the IPMN. We aimed to describe the progression in surveilled cysts after solid organ transplantation. METHODS: A prospectively maintained database of PCNs was queried for patients with IPMN. Patients who had received a previous solid organ transplantation and with ≥2 imaging studies >6 months apart after transplantation were included. Clinically relevant (CR) progression was defined as symptoms, worrisome/high-risk stigmata, or invasive carcinoma (IC). Growth ≥5 mm in 2 years is considered CR progression; size ≥3 cm alone is not. RESULTS: Between 1997 and 2023, 252 patients received solid organ transplantation (liver, 86; kidney, 113; and lung, 54) and were diagnosed as having an IPMN. This cohort was compared with a set of 770 patients surveilled for IPMN who did not have previous transplantation. Median follow-up period was 3.7 years (IQR, 1.6-6.8). Moreover, 2 transplant patients (0.8%) developed IC, and 4 developed (1.6%) high-grade dysplasia (HGD). Both were less common in transplant patients than the nontransplant population (IC, 3.3%; HGD, 2.9%), although this was not significant on time-to-event analysis (IC, P = .152; HGD, P = .352). The rate of CR progression was high in the transplant cohort (n = 118; 47%). Features of CR progression included size growth (n = 79; 67%), other worrisome/high-risk stigmata (n = 25; 21%), and new main duct involvement (n = 14; 12%). Compared with the nontransplant (n = 128; 17%), transplant patients had a higher rate of CR progression (P < .001), which was mostly explained by a more frequent size growth (31% vs 9%; P < .001). However, no transplant patients with size growth CR progression developed IC. Moreover, 17 (6.7%) required pancreatic surgery for CR progression after transplant vs 58 (7.5%) in the nontransplant population. Furthermore, 6 resected cysts (35%) harbored high-risk pathology after transplant (IC, 2; HGD, 4) vs 40 (69%) in the general population (P < .001; IC, 29; HGD, 11). CONCLUSION: Malignant transformation of BD-IPMNs is rare despite systemic immunosuppression in solid organ transplant patients. This supports transplantation in patients with IPMN without fear of worsening their risk of pancreatic cancer, although it was associated with a higher risk of disease progression. Patients with IPMNs should be surveilled with yearly scans after transplant, with pancreatic resection reserved for only high-risk features as we continue to define the optimal criteria for those with CR progression.

The Impact of Biliary Injury on the Recurrence of Biliary Cancer and Benign Disease after Liver Transplantation: Risk Factors and Mechanisms.

Liver transplantation is known to generate significant inflammation in the entire organ based on the metabolic profile and the tissue's ability to recover from the ischemia-reperfusion injury (IRI). This cascade contributes to post-transplant complications, affecting both the synthetic liver function (immediate) and the scar development in the biliary tree. The new occurrence of biliary strictures, and the recurrence of malignant and benign liver diseases, such as cholangiocarcinoma (CCA) and primary sclerosing cholangitis (PSC), are direct consequences linked to this inflammation. The accumulation of toxic metabolites, such as succinate, causes undirected electron flows, triggering the releases of reactive oxygen species (ROS) from a severely dysfunctional mitochondrial complex 1. This initiates the inflammatory IRI cascade, with subsequent ischemic biliary stricturing, and the upregulation of pro-tumorigenic signaling. Such inflammation is both local and systemic, promoting an immunocompromised status that can lead to the recurrence of underlying liver disease, both malignant and benign in nature. The traditional treatment for CCA was resection, when possible, followed by cytotoxic chemotherapy. Liver transplant oncology is increasingly recognized as a potentially curative approach for patients with intrahepatic (iCCA) and perihilar (pCCA) cholangiocarcinoma. The link between IRI and disease recurrence is increasingly recognized in transplant oncology for hepatocellular carcinoma. However, smaller numbers have prevented similar analyses for CCA. The mechanistic link may be even more critical in this disease, as IRI causes the most profound damage to the intrahepatic bile ducts. This article reviews the underlying mechanisms associated with biliary inflammation and biliary pathology after liver transplantation. One main focus is on the link between transplant-related IRI-associated inflammation and the recurrence of cholangiocarcinoma and benign liver diseases of the biliary tree. Risk factors and protective strategies are highlighted.

Long-term outcomes after hypothermic oxygenated machine perfusion and transplantation of 1,202 donor livers in a real-world setting (HOPE-REAL study).

BACKGROUND & AIMS: Despite strong evidence for improved preservation of donor livers by machine perfusion, longer post-transplant follow-up data are urgently needed in an unselected patient population. We aimed to assess long-term outcomes after transplantation of hypothermic oxygenated machine perfusion (HOPE)-treated donor livers based on real-world data (i.e., IDEAL-D stage 4). METHODS: In this international, multicentre, observational cohort study, we collected data from adult recipients of HOPE-treated livers transplanted between January 2012 and December 2021. Analyses were stratified by donation after brain death (DBD) and donation after circulatory death (DCD), sub-divided by their respective risk categories. The primary outcome was death-censored graft survival. Secondary outcomes included the incidence of primary non-function (PNF) and ischaemic cholangiopathy (IC). RESULTS: We report on 1,202 liver transplantations (64% DBD) performed at 22 European centres. For DBD, a total number of 99 benchmark (8%), 176 standard (15%), and 493 extended-criteria (41%) cases were included. For DCD, 117 transplants were classified as low risk (10%), 186 as high risk (16%), and 131 as futile (11%), with significant risk profile variations among centres. Actuarial 1-, 3-, and 5-year death-censored graft survival rates for DBD and DCD livers were 95%, 92%, and 91%, vs. 92%, 87%, and 81%, respectively (log-rank p = 0.003). Within DBD and DCD strata, death-censored graft survival was similar among risk groups (log-rank p = 0.26, p = 0.99). Graft loss due to PNF or IC was 2.3% and 0.4% (DBD), and 5% and 4.1% (DCD). CONCLUSIONS: This study shows excellent 5-year survival after transplantation of HOPE-treated DBD and DCD livers with low rates of graft loss due to PNF or IC, irrespective of their individual risk profile. HOPE treatment has now reached IDEAL-D stage 4, which further supports its implementation in routine clinical practice. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT05520320. IMPACT AND IMPLICATIONS: This study demonstrates the excellent long-term performance of hypothermic oxygenated machine perfusion (HOPE) treatment of donation after circulatory and donation after brain death liver grafts irrespective of their individual risk profile in a real-world setting, outside the evaluation of randomised-controlled trials. While previous studies have established safety, feasibility, and efficacy against the current standard, according to the IDEAL-D evaluation framework, HOPE treatment has now reached the final IDEAL-D stage 4, which further supports its implementation in routine clinical practice.

Expanding Selection Criteria in Deceased Donor Liver Transplantation for Hepatocellular Carcinoma: Long-term Follow-up of a National Registry and 2 Transplant Centers.

BACKGROUND: This study compares selection criteria for liver transplant (LT) for hepatocellular carcinoma (HCC) for inclusivity and predictive ability to identify the most permissive criteria that maintain patient outcomes. METHODS: The Scientific Registry of Transplant Recipients (SRTR) database was queried for deceased donor LT's for HCC (2003-2020) with 3-y follow-up; these data were compared with a 2-center experience. Milan, University of California, San Francisco (UCSF), 5-5-500, Up-to-seven (U7), HALT-HCC, and Metroticket 2.0 scores were calculated. RESULTS: Nationally, 26 409 patients were included, and 547 at the 2 institutions. Median SRTR-follow-up was 6.8 y (interquartile range 3.9-10.1). Three criteria allowed the expansion of candidacy versus Milan: UCSF (7.7%, n = 1898), Metroticket 2.0 (4.2%, n = 1037), and U7 (3.5%, n = 828). The absolute difference in 3-y overall survival (OS) between scores was 1.5%. HALT-HCC (area under the curve [AUC] = 0.559, 0.551-0.567) best predicted 3-y OS although AUC was notably similar between criteria (0.506 < AUC < 0.527, Mila n = 0.513, UCSF = 0.506, 5-5-500 = 0.522, U7 = 0.511, HALT-HCC = 0.559, and Metroticket 2.0 = 0.520), as was Harrall's c-statistic (0.507 < c-statistic < 0.532). All scores predicted survival to P < 0.001 on competing risk analysis. Median follow-up in our enterprise was 9.8 y (interquartile range 7.1-13.3). U7 (13.0%, n = 58), UCSF (11.1%, n = 50), HALT-HCC (6.4%, n = 29), and Metroticket 2.0 (6.3%, n = 28) allowed candidate expansion. HALT-HCC (AUC = 0.768, 0.713-0.823) and Metroticket 2.0 (AUC = 0.739, 0.677-0.801) were the most predictive of recurrence. All scores predicted recurrence and survival to P < 0.001 using competing risk analysis. CONCLUSIONS: Less restrictive criteria such as Metroticket 2.0, UCSF, or U7 allow broader application of transplants for HCC without sacrificing outcomes. Thus, the criteria for Model for End-stage Liver Disease-exception points for HCC should be expanded to allow more patients to receive life-saving transplantation.

Tumor Mutational Burden From Circulating Tumor DNA Predicts Recurrence of Hepatocellular Carcinoma After Resection: An Emerging Biomarker for Surveillance.

OBJECTIVE: Describe the utility of circulating tumor DNA in the postoperative surveillance of hepatocellular carcinoma (HCC). BACKGROUND: Current biomarkers for HCC like alpha-fetoprotein (AFP) are lacking. Circulating tumor DNA (ctDNA) has shown promise in colorectal and lung cancers, but its utility in HCC remains relatively unknown. METHODS: Patients with HCC undergoing curative-intent resection from November 1, 2020, to July 1, 2023, received ctDNA testing using the Guardant360 platform. Tumor mutational burden (TMB) is calculated as the number of somatic mutations-per-megabase of genomic material identified. RESULTS: Forty-seven patients had postoperative ctDNA testing. The mean follow-up was 27 months, and the maximum was 43.2 months. Twelve patients (26%) experienced recurrence. Most (n=41/47, 87.2%) had identifiable ctDNA postoperatively; 55.3% (n=26) were TMB-not detected versus 45.7% (n=21) TMB-detectable. Postoperative identifiable ctDNA was not associated with RFS ( P =0.518). Detectable TMB was associated with reduced RFS (6.9 vs 14.7 mo, P =0.049). There was a higher rate of recurrence in patients with TMB (n=9/21, 42.9%, vs n=3/26, 11.5%, P =0.02). Area under the curve for TMB-prediction of recurrence was 0.752 versus 0.550 for AFP. ROC analysis established a TMB cutoff of 4.8mut/mB for predicting post-operative recurrence ( P =0.002) and RFS ( P =0.025). AFP was not correlated with RFS using the lab-normal cutoff (<11 ng/mL, P =0.682) or the cutoff established by ROC analysis (≥4.6 ng/mL, P =0.494). TMB-high was associated with poorer RFS on cox-regression analysis (hazard ratio=5.386, 95% CI: 1.109-26.160, P =0.037), while microvascular invasion ( P =0.853) and AFP ( P =0.439) were not. CONCLUSIONS: Identifiable TMB on postoperative ctDNA predicts HCC recurrence and outperformed AFP in this cohort. Perioperative ctDNA may be a useful surveillance tool following curative-intent hepatectomy. Larger-scale studies are needed to confirm this utility and investigate additional applications in HCC patients, including the potential for prophylactic treatment in patients with residual TMB after resection.

Intensive locoregional therapy before liver transplantation for colorectal cancer liver metastasis: A novel pretransplant protocol.

We describe a novel pre-liver transplant (LT) approach in colorectal liver metastasis, allowing for improved monitoring of tumor biology and reduction of disease burden before committing a patient to transplantation. Patients undergoing LT for colorectal liver metastasis at Cleveland Clinic were included. The described protocol involves intensive locoregional therapy with systemic chemotherapy, aiming to reach minimal disease burden revealed by positron emission tomography scan and carcinoembryonic Ag. Patients with no detectable disease or irreversible treatment-induced liver injury undergo transplant. Nine patients received liver transplant out of 27 who were evaluated (33.3%). The median follow-up was 700 days. Seven patients (77.8%) received a living donor LT. Five had no detectable disease, and 4 had treatment-induced cirrhosis. Pretransplant management included chemotherapy (n = 9) +/- bevacizumab (n = 6) and/or anti-EGFR (n = 6). The median number of pre-LT cycles of chemotherapy was 16 (range 10-40). Liver-directed therapy included Yttrium-90 (n = 5), ablation (n = 4), resection (n = 4), and hepatic artery infusion pump (n = 3). Three patients recurred after LT. Actuarial 1- and 2-year recurrence-free survival were 75% (n = 6/8) and 60% (n = 3/5). Recurrence occurred in the lungs (n = 1), liver graft (n = 1), and lungs+para-aortic nodes (n = 1). Patients with pre-LT detectable disease had reduced RFS ( p = 0.04). All patients with recurrence had histologically viable tumors in the liver explant. Patients treated in our protocol (n = 16) demonstrated improved survival versus those who were not candidates (n = 11) regardless of transplant status ( p = 0.01). A protocol defined by aggressive pretransplant liver-directed treatment and transplant for patients with the undetectable disease or treatment-induced liver injury may help prevent tumor recurrence.

Harmonizing Definitions and Perspectives in Extreme Liver Surgery: A Delphi Experts Consensus.

OBJECTIVE: To propose to our community a common language about extreme liver surgery. BACKGROUND: The lack of a clear definition of extreme liver surgery prevents convincing comparisons of results among centers. METHODS: We used a two-round Delphi methodology to quantify consensus among liver surgery experts. For inclusion in the final recommendations, we established a consensus when the positive responses (agree and totally agree) exceeded 70%. The study steering group summarized and reported the recommendations. In general, a five-point Likert scale with a neutral central value was used, and in a few cases multiple choices. Results are displayed as numbers and percentages. RESULTS: A two-round Delphi study was completed by 38 expert surgeons in complex hepatobiliary surgery. The surgeon´s median age was 58 years old (52-63) and the median years of experience was 25 years (20-31). For the proposed definitions of total vascular occlusion, hepatic flow occlusion and inferior vein occlusion, the degree of agreement was 97%, 81% and 84%, respectively. In situ approach (64%) was the preferred, followed by ante situ (22%) and ex situ (14%). Autologous or cadaveric graft for hepatic artery or hepatic vein repair were the most recommended (89%). The use of veno-venous bypass or portocaval shunt revealed the divergence depending on the case. Overall, 75% of the experts agreed with the proposed definition for extreme liver surgery. CONCLUSION: Obtaining a consensus on the definition of extreme liver surgery is essential to guarantee the correct management of patients with highly complex hepatobiliary oncological disease. The management of candidates for extreme liver surgery involves comprehensive care ranging from adequate patient selection to the appropriate surgical strategy.

The impact of normothermic machine perfusion and acuity circles on waitlist time, mortality, and cost in liver transplantation: A multicenter experience.

Ex situ normothermic machine perfusion (NMP) helps increase the use of extended criteria donor livers. However, the impact of an NMP program on waitlist times and mortality has not been evaluated. Adult patients listed for liver transplant (LT) at 2 academic centers from January 1, 2015, to September 1, 2023, were included (n=2773) to allow all patients ≥6 months follow-up from listing. Routine NMP was implemented on October 14, 2022. Waitlist outcomes were compared from pre-NMP pre-acuity circles (n=1460), pre-NMP with acuity circles (n=842), and with NMP (n=381). Median waitlist time was 79 days (IQR: 20-232 d) at baseline, 49 days (7-182) with acuity circles, and 14 days (5-56) with NMP ( p <0.001). The rate of transplant-per-100-person-years improved from 61-per-100-person-years to 99-per-100-person-years with acuity circles and 194-per-100-person-years with NMP ( p <0.001). Crude mortality without transplant decreased from 18.3% (n=268/1460) to 13.3% (n=112/843), to 6.3% (n=24/381) ( p <0.001) with NMP. The incidence of mortality without LT was 15-per-100-person-years before acuity circles, 19-per-100 with acuity circles, and 9-per-100-person-years after NMP ( p <0.001). Median Model for End-Stage Liver Disease at LT was lowest with NMP, but Model for End-Stage Liver Disease at listing was highest in this era ( p <0.0001). The median donor risk index of transplanted livers at baseline was 1.54 (1.27-1.82), 1.66 (1.42-2.16) with acuity circles, and 2.06 (1.63-2.46) with NMP ( p <0.001). Six-month post-LT survival was not different between eras ( p =0.322). The total cost of health care while waitlisted was lowest in the NMP era ($53,683 vs. $32,687 vs. $23,688, p <0.001); cost-per-day did not differ between eras ( p =0.152). The implementation of a routine NMP program was associated with reduced waitlist time and mortality without compromising short-term survival after liver transplant despite increased use of riskier grafts. Routine NMP use enables better waitlist management with reduced health care costs.

Early Detection and Monitoring of Anastomotic Leaks via Naked Eye-Readable, Non-Electronic Macromolecular Network Sensors.

Anastomotic leakage (AL) is the leaking of non-sterile gastrointestinal contents into a patient's abdominal cavity. AL is one of the most dreaded complications following gastrointestinal surgery, with mortality rates reaching up to 27%. The current diagnostic methods for anastomotic leaks are limited in sensitivity and specificity. Since the timing of detection directly impacts patient outcomes, developing new, fast, and simple methods for early leak detection is crucial. Here, a naked eye-readable, electronic-free macromolecular network drain fluid sensor is introduced for continuous monitoring and early detection of AL at the patient's bedside. The sensor array comprises three different macromolecular network sensing elements, each tailored for selectivity toward the three major digestive enzymes found in the drainage fluid during a developing AL. Upon digestion of the macromolecular network structure by the respective digestive enzymes, the sensor produces an optical shift discernible to the naked eye. The diagnostic efficacy and clinical applicability of these sensors are demonstrated using clinical samples from 32 patients, yielding a Receiver Operating Characteristic Area Under the Curve (ROC AUC) of 1.0. This work has the potential to significantly contribute to improved patient outcomes through continuous monitoring and early, low-cost, and reliable AL detection.

Machine perfusion in liver transplantation: recent advances and coming challenges.

PURPOSE OF REVIEW: Machine perfusion has been adopted into clinical practice in Europe since the mid-2010s and, more recently, in the United States (US) following approval of normothermic machine perfusion (NMP). We aim to review recent advances, provide discussion of potential future directions, and summarize challenges currently facing the field. RECENT FINDINGS: Both NMP and hypothermic-oxygenated perfusion (HOPE) improve overall outcomes after liver transplantation versus traditional static cold storage (SCS) and offer improved logistical flexibility. HOPE offers additional protection to the biliary system stemming from its' protection of mitochondria and lessening of ischemia-reperfusion injury. Normothermic regional perfusion (NRP) is touted to offer similar protective effects on the biliary system, though this has not been studied prospectively.The most critical question remaining is the optimal use cases for each of the three techniques (NMP, HOPE, and NRP), particularly as HOPE and NRP become more available in the US. There are additional questions regarding the most effective criteria for viability assessment and the true economic impact of these techniques. Finally, with each technique purported to allow well tolerated use of riskier grafts, there is an urgent need to define terminology for graft risk, as baseline population differences make comparison of current data challenging. SUMMARY: Machine perfusion is now widely available in all western countries and has become an essential tool in liver transplantation. Identification of the ideal technique for each graft, optimization of viability assessment, cost-effectiveness analyses, and proper definition of graft risk are the next steps to maximizing the utility of these powerful tools.

Small graft size and hepatocellular carcinoma outcomes in living donor liver transplantation: a retrospective multicentric cohort study.

INTRODUCTION: This study examined associations between the graft-to-recipient weight ratio (GRWR) for adult-to-adult living donor liver transplantation (LDLT) and hepatocellular carcinoma (HCC) outcomes. MATERIALS AND METHODS: Data from patients in the Korean Organ Transplantation Registry who underwent LDLT for HCC from 2014 to 2021 were retrospectively reviewed. Patients were categorized using the cutoff GRWR for HCC recurrence determined by an adjusted cubic spline (GRWR <0.7% vs. GRWR ≥0.7%). Recurrence-free survival (RFS) and HCC recurrence were analyzed in the entire and a 1:5 propensity-matched cohort. RESULTS: The eligible cohort consisted of 2005 LDLT recipients [GRWR <0.7 ( n =59) vs. GRWR ≥0.7 ( n =1946)]. In the entire cohort, 5-year RFS was significantly lower in the GRWR <0.7 than in the GRWR ≥0.7 group (66.7% vs. 76.7%, P =0.019), although HCC recurrence was not different between groups (77.1% vs. 80.7%, P =0.234). This trend was similar in the matched cohort ( P =0.014 for RFS and P =0.096 for HCC recurrence). In multivariable analyses, GRWR <0.7 was an independent risk factor for RFS [adjusted hazard ratio (aHR) 1.89, P =0.012], but the result was marginal for HCC recurrence (aHR 1.61, P =0.066). In the pretransplant tumor burden subgroup analysis, GRWR <0.7 was a significant risk factor for both RFS and HCC recurrence only for tumors exceeding the Milan criteria (aHR 3.10, P <0.001 for RFS; aHR 2.92, P =0.003 for HCC recurrence) or with MoRAL scores in the fourth quartile (aHR 3.33, P <0.001 for RFS; aHR 2.61, P =0.019 for HCC recurrence). CONCLUSIONS: A GRWR <0.7 potentially leads to lower RFS and higher HCC recurrence after LDLT when the pretransplant tumor burden is high.

Routine utilization of machine perfusion in liver transplantation: Ready for prime time?

The last decade has been notable for increasing high-quality research and dramatic improvement in outcomes with dynamic liver preservation. Robust evidence from numerous randomized controlled trials has been pooled by meta-analyses, providing the highest available evidence on the protective effect of machine perfusion (MP) over static cold storage in liver transplantation (LT). Based on a protective effect with less complications and improved graft survival, the field has seen a paradigm shift in organ preservation. This editorial focuses on the role of MP in LT and how it could become the new "gold standard". Strong collaborative efforts are needed to explore its effects on long-term outcomes.

Efficiency of machine perfusion in pediatric liver transplantation.

Liver transplantation is the only life-saving procedure for children with end-stage liver disease. The field is however heterogenic with various graft types, recipient age, weight, and underlying diseases. Despite recently improved overall outcomes and the expanded use of living donors, waiting list mortality remains unacceptable, particularly in small children and infants. Based on the known negative effects of elevated donor age, higher body mass index, and prolonged cold ischemia time, the number of available donors for pediatric recipients is limited. Machine perfusion has regained significant interest in the adult liver transplant population during the last decade. Ten randomized controlled trials are published with an overall advantage of machine perfusion techniques over cold storage regarding postoperative outcomes, including graft survival. The concept of hypothermic oxygenated perfusion (HOPE) was the first and only perfusion technique used for pediatric liver transplantation today. In 2018 the first pediatric candidate received a full-size graft donated after circulatory death with cold storage and HOPE, followed by a few split liver transplants after HOPE with an overall limited case number until today. One series of split procedures during HOPE was recently presented by colleagues from France with excellent results, reduced complications, and better graft survival. Such early experience paves the way for more systematic use of machine perfusion techniques for different graft types for pediatric recipients. Clinical reports of pediatric liver transplants with other perfusion techniques are awaited. Strong collaborative efforts are needed to explore the effect of perfusion techniques in this vulnerable population impacting not only the immediate posttransplant outcome but the development and success of an entire life.