Immunotherapy as a Downstaging Tool for Liver Transplantation in Hepatocellular Carcinoma

Liver Transplantation for Hepatocellular Carcinoma: An Expanding Cornerstone of Care in the Era of Immunotherapy

Liver transplantation (LT) has been accepted as a cornerstone of care in hepatocellular carcinoma (HCC) for almost three decades. In recent years, its role has been evolving to include patients with disease burden beyond the widely used Milan criteria. The integration of dynamic biomarkers such as alpha-fetoprotein together with downstaging approaches and tumor evolution after enlistment has allowed the selection of patients most likely to benefit, resulting in 5-year survival rates greater that 70%. With the increasing use of immune checkpoint inhibitors (ICIs) across all stages of disease, alone or in combination with locoregional therapies, there is now the potential to further expand the patient population with HCC who may benefit from LT. This brings challenges, given the global shortage of organs and the need to better understand the optimal use of ICIs before transplantation. Furthermore, the field of transplant oncology awaits additional biomarkers that can predict those likely to benefit from ICIs. More than ever, a multidisciplinary approach for liver cancer management is critical to ensure all patients are considered for LT where appropriate, and do not miss the opportunity for long-term survival.

Risk of transplant rejection associated with ICIs prior to liver transplantation in HCC: A multicenter retrospective study

BACKGROUND

Studies on the safety of immune checkpoint inhibitors (ICIs) prior to liver transplantation (LT) are still limited to case reports or case series. It is vital to be aware of possible risk of transplant rejection with regards to ICIs after LT.

OBJECTIVE

To explore the possible risk of transplant rejection induced by ICIs in hepatocellular carcinoma (HCC) patients and investigate the safe washout interval between ICIs administration and LT.

METHODS

HCC patients from 3 tertiary hospitals in China who received ICIs prior to LT over the past 5 years were analyzed retrospectively. Patients who had experienced transplant rejection were reported in detail. Additionally, a comprehensive search of databases was conducted to identify case reports of HCC patients who underwent LT after receiving ICIs until October 1, 2024.

RESULTS

In our study, a total of 25 patients were analyzed. Programmed cell death protein 1 (PD-1) inhibitors were most commonly used (68 %, 17/25). The median interval between the last dose of ICIs and LT was 64 (40-150.75) days. Three patients (12 %) experienced T-cell mediated rejection (TCMR), 1 of which was induced by ICIs, and the other 2 of which could not be excluded from the influence of immunosuppressant concentrations. In literature review, a total of 96 cases of HCC patients who had received ICIs prior to LT were included. PD-1 inhibitor monotherapy resulted in significantly higher rejection than PD-L1 inhibitor monotherapy and other ICIs combination regimens (P = 0.021). In patients with pembrolizumab, the interval from ICIs to LT was shorter in the rejection group than in the non-rejection group (P = 0.045). Twenty-one cases (21.88 %) experienced transplant rejection, and 3 patients passed away following transplant rejection.

CONCLUSION

ICIs prior to LT was associated with the risk of transplant rejection, especially with factors such as the type of ICIs and the interval between ICIs and LT. Multicenter prospective studies are needed to further explore the safety of ICIs.

APASL clinical practice guidelines on systemic therapy for hepatocellular carcinoma-2024

In Asia-Pacific region, hepatocellular carcinoma is a serious health threat attributing to over 600,000 deaths each year and account for over 70% of global cases. Clinically, the major unmet needs are recurrence after curative-intent surgery, liver transplantation or local ablation and disease progression in those with hepatocellular carcinoma not eligible for resection or failed locoregional therapy. In the recent few years, new targeted therapy and immune-checkpoint inhibitors have been registered as systemic therapy to address these issues. Notably, new forms of systemic therapy, either as first-line or second-line therapy for unresectable hepatocellular or those not eligible for locoregional therapy, are now available. New data is also emerging with the use of systemic therapy to prevent hepatocellular carcinoma recurrence after curative-intent resection or local ablation therapy and to retard disease progression after locoregional therapy. In the future, further implementation of immune-checkpoint inhibitors and other forms of immunotherapy are expected to bring a new paradigm to the management of hepatocellular carcinoma. New insight related to immune-related adverse events with the use of immunotherapy has allso enabled optimization of the therapeutic approach to patients with hepatocellular carcinoma. The purpose of this clinical practice guideline is to provide an up-to-date recommendation based on clinical evidence and experience from expert Asia-Pacific key opinion leaders in the field of hepatocellular carcinoma. Three key questions will be addressed, namely: (1) Which patients with hepatocellular carcinoma should be considered for systemic therapy? (2) Which systemic therapy should be used? (3) How should a patient planned for immune checkpoint-based systemic therapy be managed and monitored?

Liver resection and transplantation in the era of checkpoint inhibitors

Immune checkpoint inhibitors (ICIs) have revolutionised the treatment landscape for advanced hepatocellular carcinoma (HCC). The combination of atezolizumab and bevacizumab has demonstrated efficacy, establishing a new standard of care for advanced HCC. Neoadjuvant studies have shown promising results with high response rates, increasing research into ICIs' role. In the peri-operative setting, in addition to adjuvant and neo-adjuvant therapies, strategies for "downstaging" and "bridging" patients to liver transplantation (LT) are being investigated, broadening the eligible candidate pool. Furthermore, therapeutic advances have reshaped conversion strategies for hepatic resection, with emerging evidence indicating a role for adjuvant immunotherapy in patients at high risk of postoperative recurrence. In LT, concerns have arisen over the potential conflict between immunosuppression needs and the immune-enhancing effects of ICIs, with reports of severe rejection. However, liver-specific factors may lessen rejection risks, prompting exploration into the safety of pre-transplant ICI administration. Moreover, ongoing trials must prioritise patient selection and vigilant management protocols. Despite the remarkable progress in immunotherapy, the intricate molecular interactions within the tumour microenvironment and their implications on oncogenic pathways remain incompletely understood. This highlights the need for specialised expertise to effectively integrate immunotherapy into the surgical management of HCC. Key challenges include ensuring safety, optimising oncological outcomes, managing the risk of graft rejection in transplant recipients, and refining patient selection criteria. In this review, we aim to provide a comprehensive overview of the evolving role of immunotherapy in the surgical management of HCC, discussing the rationale for its application in both pre- and post-surgical contexts, leveraging current clinical experience, identifying potential limitations, and envisioning future applications. By integrating existing knowledge and highlighting areas for further investigation, this review seeks to inform clinical practice and guide future research endeavours.

Immune Checkpoint Inhibitors in the Pre-Transplant Hepatocellular Carcinoma Setting: A Glimpse Beyond the Liver

Hepatocellular carcinoma (HCC) is the most common primary liver cancer and the third leading cause of cancer-related death worldwide. Liver transplantation (LT) is the best therapy for most patients with non-metastatic HCC. In recent years, the management of patients with HCC has considerably changed, thanks to the improvement of molecular biology knowledge and the introduction of immunotherapy. To date, systemic therapy is authorized in the Western world only in patients with advanced HCC. However, this therapy could not only stabilize the tumour disease or improve survival but could display excellent response and lead to downstaging of the tumour that finally permits LT. There are increasing reports of patients that have performed LT after pretreatment with immune checkpoint inhibitors (ICIs). However, due to the intrinsic mechanism of ICIs, graft rejection might be favoured. In addition, chronic adverse effects affecting other organs may also appear after the end of therapy. This review aims to evaluate the readiness and outcomes of LT in patients with advanced HCC who have previously undergone treatment with ICIs. It seeks to identify the challenges, risks, and benefits associated with this conversion therapy. The integration of ICIs into the treatment paradigm for advanced HCC necessitates a nuanced approach to LT. While early evidence supports the feasibility of LT following ICIs therapy, there is an urgent need for standardized guidelines and more extensive longitudinal studies to optimize patient selection, timing, and post-transplant management.

Pretransplant use of immune checkpoint inhibitors for hepatocellular carcinoma: A multicenter, retrospective cohort study

Immune checkpoint inhibitors (ICIs) as a downstaging or bridging therapy for liver transplantation (LT) in hepatocellular carcinoma patients are rapidly increasing. However, the evidence about the feasibility and safety of pre-LT ICI therapy is limited and controversial. To this end, a multicenter, retrospective cohort study was conducted in 11 Chinese centers. The results showed that 83 recipients received pre-LT ICI therapy during the study period. The median post-LT follow-up was 8.1 (interquartile range 3.3-14.6) months. During the short follow-up, 23 (27.7%) recipients developed allograft rejection, and 7 of them (30.4%) were diagnosed by liver biopsy. Multivariate logistics regression analysis showed that the time interval between the last administration of ICI therapy and LT (TLAT) ≥ 30 days was an independent protective factor for allograft rejection (odds ratio = 0.096, 95% confidence interval 0.026-0.357; P < .001). Multivariate Cox analysis showed that allograft rejection was an independent risk factor for overall survival (hazard ratio = 9.960, 95% confidence interval 1.006-98.610; P = .043). We conclude that patients who receive a pre-LT ICI therapy with a TLAT shorter than 30 days have a much higher risk of allograft rejection than those with a TLAT longer than 30 days. The presence of rejection episodes might be associated with higher post-LT mortality.

Immune checkpoint inhibitors in liver transplantation: Current practice, challenges, and opportunities

Immune checkpoint inhibitors are becoming a mainstay of cancer treatment. While first studied and approved for patients with unresectable disease, due to their efficacy, they are becoming increasingly used in the perioperative period across many cancer types. In patients with HCC, immune checkpoint inhibitors have now become the standard of care in the advanced setting and have shown promising results in the adjuvant setting after liver resection. While these drugs continue to show promise, their role in the peritransplant setting still remains a question. In this review, we explore the current use of this class of medications in patients with HCC, as well as the immunologic role of the pathways that they inhibit. We also identify potential for future research opportunities to better understand the role of these medications.

Liver Transplantation for Hepatocellular Carcinoma in the Era of Immune Checkpoint Inhibitors

Hepatocellular carcinoma (HCC) remains the leading oncological indication for liver transplantation (LT), with evolving and broadened inclusion criteria. Immune checkpoint inhibitors (ICIs) gained a central role in systemic HCC treatment and showed potential in the peri-transplant setting as downstaging/bridging therapy before LT or as a treatment for HCC recurrence following LT. However, the antagonistic mechanisms of action between ICIs and immunosuppressive drugs pose significant challenges, particularly regarding the risk of acute rejection (AR). This review analyzes the main signaling pathways targeted by ICI therapies and summarizes current studies on ICI therapy before and after LT. The literature on this topic is limited and highly heterogeneous, precluding definitive evidence-based conclusions. The use of ICIs before LT appears promising, provided that a sufficient wash-out period is implemented. In contrast, the results of post-LT ICI therapy do not support its wide clinical application due to high AR rates and overall poor response to treatment. In the future, modern graft preservation techniques might support the selection of good ICI responders, but data from high-level studies are urgently needed.

Downstaging Hepatocellular Carcinoma with Checkpoint Inhibitor Therapy Improves Access to Curative Liver Transplant

PURPOSE

Liver transplantation is curative for hepatocellular carcinoma (HCC). Checkpoint inhibitor therapy (CPIT) has been used in unresectable HCC, but recent advances have demonstrated CPIT as an innovative method of downstaging advanced HCC with the caveat that CPIT prior to transplantation has risks including irreversible graft rejection. We report the outcomes of Mayo Clinic Arizona patients who underwent downstaging with CPIT.

METHODS

This retrospective chart review was conducted for Mayo Clinic Arizona patients who were diagnosed with HCC who underwent downstaging with CPIT with the goal of meeting criteria for transplantation.

RESULTS

We present nine cases with HCC outside Milan who underwent CPIT. Four received a transplant; one was delisted due to his exceptional therapeutic response. All received liver-directed therapy. Peak alpha-fetoprotein pre-CPIT ranged from 8-29,523 ng/mL, which decreased to 2.2-19.6 ng/mL on CPIT. CPIT included atezolizumab/bevacizumab, ipilimumab/nivolumab, nivolumab, and pembrolizumab; one patient received two regimens. CPIT was held prior to transplant at a median of 3 months. Three patients received methylprednisolone for immunosuppression induction; one received thymoglobulin. One patient developed acute cellular rejection at 5 weeks, 9 weeks, and 5 months post-transplant; given the late onset, these were not attributed to CPIT and were successfully treated. During an average follow-up of 16.5 months, no tumor recurrence has occurred.

CONCLUSION

We describe nine patients with HCC outside Milan with inadequate response with liver-directed therapy, who achieved marked responses with CPIT, allowing for consideration of successful liver transplantation. Our case series supports the consideration of locoregional therapies and CPIT for downstaging to within transplant criteria.

Systemic Therapy for Advanced Hepatocellular Carcinoma: ASCO Guideline Update

PURPOSE

To update an evidence-based guideline to assist in clinical decision-making for patients with advanced hepatocellular carcinoma (HCC).

METHODS

ASCO convened an Expert Panel to update the 2020 guideline on systemic therapy for HCC. The panel updated the systematic review to include randomized controlled trials (RCTs) published through October 2023 and updated recommendations.

RESULTS

Ten new RCTs met the inclusion criteria and were added to the evidence base.

RECOMMENDATIONS

Atezolizumab + bevacizumab (atezo + bev) or durvalumab + tremelimumab (durva + treme) may be offered first-line for patients with advanced HCC, Child-Pugh class A liver disease, and Eastern Cooperative Oncology Group performance status 0-1. Where there are contraindications to these therapies, sorafenib, lenvatinib, or durvalumab may be offered first-line. Following first-line treatment with atezo + bev, second-line therapy with a tyrosine kinase inhibitor (TKI), ramucirumab (for patients with alpha-fetoprotein [AFP] ≥400 ng/mL), durva + treme, or nivolumab + ipilimumab (nivo + ipi) may be recommended for appropriate candidates. Following first-line therapy with durva + treme, second-line therapy with a TKI is recommended. Following first-line treatment with sorafenib or lenvatinib, second-line therapy options include cabozantinib, regorafenib for patients who previously tolerated sorafenib, ramucirumab (AFP ≥400 ng/mL), nivo + ipi, or durvalumab; atezo + bev or durva + treme may be considered for patients who did not have access to these therapies in the first-line setting, and do not have contraindications. Pembrolizumab or nivolumab are also options for appropriate patients following sorafenib or lenvatinib. Third-line therapy may be considered in Child-Pugh class A patients with good PS, using one of the agents listed previously that has a nonidentical mechanism of action with previously received therapy. A cautious approach to systemic therapy is recommended for patients with Child-Pugh class B advanced HCC. Further guidance on choosing between options is included within the guideline.Additional information is available at www.asco.org/gastrointestinal-cancer-guidelines.

Immunotherapy for transplantation of hepatocellular carcinoma: the next frontier in adjunctive therapy

PURPOSE OF REVIEW

The increasing success of liver transplantation in hepatocellular carcinoma (HCC) drives an ever-evolving search for innovative strategies to broaden eligible patients' pools. Recent advances in immuno-oncology have turned the spotlight on immune checkpoint inhibitors (ICIs). This review offers an updated overview of ICIs in liver transplantation for HCC, exploring neoadjuvant and adjuvant approaches and addressing unanswered questions on safety, patients' selection, and response predictors.

RECENT FINDINGS

ICIs have transitioned from being a last-chance therapeutic hope to becoming an integral cornerstone in the treatment of advanced HCC, holding great promise as a compelling option not only to downstage patients for transplantation but also as an alternative strategy in addressing posttransplantation disease recurrence. Despite ongoing refinements in immunotherapeutic agents, the complex molecular pathways involved emphasize the need for a comprehensive approach to integrate immunotherapy in liver transplantation.

SUMMARY

Initial concerns about graft rejection, with ICIs as a bridging therapy to liver transplantation, were successfully addressed using adequate immunosuppressants strategies and minimized with a sufficient washout period. Post-liver transplantation disease recurrence remains challenging, requiring a balance between effective therapy and preserving graft function. Emphasis should be placed on clinical trials validating the risk-benefit ratio of ICIs for liver transplantation, guiding appropriate patients' selection, and establishing clear management pathways.

Liver Transplantation for Hepatocellular Carcinoma: A Narrative Review and A Glimpse into The Future

Liver transplantation (LT) is a highly effective treatment for carefully selected patients with hepatocellular carcinoma (HCC). In this review, we explored the development of LT selection criteria and organ allocation policies, comparing original data to underscore their historical progression into the intricate task of quantitatively estimating pre- and post-LT survivals. We emphasized the role of biomarkers such as serum alpha-fetoprotein, Des-gamma-carboxy-prothrombin, circulating tumor cells, and circulating tumor DNA in predicting patient outcomes. Additionally, we examined the transplant-associated survival benefits and the difficulties in accurately calculating these benefits. We also reviewed recent advancements in targeted therapy and checkpoint inhibitors for advanced, inoperable HCC and projected their integration into LT for HCC. We further discussed the growing use of living donor liver transplants in the United States and compared its outcomes with those of deceased donor liver transplants. Furthermore, we examined the progress in machine perfusion techniques, which have shown potential in improving patient outcomes and enlarging the donor pool. These advancements present opportunities to enhance LT patient survivals, refine selection criteria, establish new priority metrics, develop innovative bridging and downstaging strategies, and formulate redesigned LT strategies for HCC treatments.

Immunotherapy and Liver Transplantation: The Future or the Failure?

A quarter century has passed since the milestone study by Mazzaferro and colleagues on liver transplantation (LT) for hepatocellular carcinoma (HCC). The increasing demand for LT for HCC has led to the continued efforts to expand LT indications. Downstaging to within Milan criteria has been incorporated into the organ allocation policy for HCC in the United States in 2017 and provides acceptable long-term survival. The present review focuses on the rationale of neoadjuvant immune checkpoint inhibitor (ICI) in HCC, the experience of ICI in the pre- and posttransplant setting.

Transplant Oncology: An Emerging Discipline of Cancer Treatment

Transplant oncology is an emerging concept of cancer treatment with a promising prospective outcome. The applications of oncology, transplant medicine, and surgery are the core of transplant oncology to improve patients' survival and quality of life. The main concept of transplant oncology is to radically cure cancer by removing the diseased organ and replacing it with a healthy one, aiming to improve the survival outcomes and quality of life of cancer patients. Subsequently, it seeks to expand the treatment options and research for hepatobiliary malignancies, which have seen significantly improved survival outcomes after the implementation of liver transplantation (LT). In the case of colorectal cancer (CRC) in the transplant setting, where the liver is the most common site of metastasis of patients who are considered to have unresectable disease, initial studies have shown improved survival for LT treatment compared to palliative therapy interventions. The indications of LT for hepatobiliary malignancies have been slowly expanded over the years beyond Milan criteria in a stepwise manner. However, the outcome improvements and overall patient survival are limited to the specifics of the setting and systematic intervention options. This review aims to illustrate the representative concepts and history of transplant oncology as an emerging discipline for the management of hepatobiliary malignancies, in addition to other emerging concepts, such as the uses of immunotherapy in a peri-transplant setting as well as the use of circulating tumor DNA (ctDNA) for surveillance post-transplantation.

Hepatocellular Carcinoma: The Role of Immunotherapy and Transplantation in the Era of Transplant Oncology

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer deaths worldwide. As most patients present with advanced disease, curative therapy such as surgical resection and radiofrequency ablation are rarely utilized. With the advent of immunotherapy, historical treatment approaches such as liver transplantation are being challenged. In particular, the use of immune checkpoint inhibitors (ICIs) has emerged as a safe and useful option in the treatment of HCC. However, there is concern over adverse effects, such as graft rejection and graft loss. This updated review discusses the role of immunotherapy in the pre- and post-transplantation setting and provides insights into the potential of immunotherapy as an adjunct to liver transplantation. We deliberate on the use of ICI in the setting of the Milan criteria as well as the University of California San Francisco's expanded criteria for liver transplantation. Current data suggest that ICI has utility, especially in the pretransplantation setting. Nevertheless, larger, purposefully designed clinical trials are needed to clearly identify patients who will benefit most from ICI treatment in the transplant setting and determine parameters that will minimize the risk of graft rejection and maximize the benefits of this adjunct treatment.

Immunotherapy and Liver Transplantation: A Narrative Review of Basic and Clinical Data

Immune checkpoint inhibitors (ICIs) have improved the management of patients with intermediate- and advanced-stage HCC, even making some of them potential candidates for liver transplantation. However, acute rejection has been observed after ICI therapy, challenging its safety in transplant settings. We summarize the key basic impact of immune checkpoints on HCC and liver transplantation. We analyze the available case reports and case series on the use of ICI therapy prior to and after liver transplantation. A three-month washout period is desirable between ICI therapy and liver transplantation to reduce the risk of acute rejection. Whenever possible, ICIs should be avoided after liver transplantation, and especially so early after a transplant. Globally, more robust prospective data in the field are required.

Evolving Landscape in Liver Transplantation for Hepatocellular Carcinoma: From Stage Migration to Immunotherapy Revolution

Liver transplantation (LT) represents the primary curative option for HCC. Despite the extension of transplantation criteria and conversion with down-staging loco-regional treatments, transplantation is not always possible. The introduction of new standards of care in advanced HCC including a combination of immune checkpoint inhibitor-based therapies led to an improvement in response rates and could represent a promising strategy for down-staging the tumor burden. In this review, we identify reports and series, comprising a total of 43 patients who received immune checkpoint inhibitors as bridging or down-staging therapies prior to LT. Overall, treated patients registered an objective response rate of 21%, and 14 patients were reduced within the Milan criteria. Graft rejection was reported in seven patients, resulting in the death of four patients; in the remaining cases, LT was performed safely after immunotherapy. Further investigations are required to define the duration of immune checkpoint inhibitors, their minimum washout period and the LT long-term safety of this strategy. Some randomized clinical trials including immunotherapy combinations, loco-regional treatment and/or tyrosine kinase inhibitors are ongoing and will likely determine the appropriateness of immune checkpoint inhibitors' administration before LT.

Preoperative Immunotherapy in Hepatocellular Carcinoma: Current State of the Art

Hepatocellular carcinoma (HCC) is a malignancy that requires multidisciplinary evaluation to develop individualized and tailored treatment concepts. While liver resection and transplantation represent the mainstay of curative treatment in patients with early-stage HCC, disease recurrence remains an important burden. Immune checkpoint inhibitors (ICI) have become standard of care in the palliative setting, achieving promising response rates with overall good tolerability. Accordingly, ICIs are being evaluated in (neo)adjuvant concepts in order to improve survival. Nevertheless, neoadjuvant therapies are not recommended by current guidelines as they have not been proven to improve the outcome in large Phase III trials yet. Especially in the context of liver transplantation (LT), perioperative ICI usage is in need of a particularly critical risk-benefit assessment, as the immunotherapy may significantly increase the risk of rejection. In this review, we summarize available data on ICI-based perioperative treatment strategies in HCC. We discuss current drawbacks and challenges of this treatment concept and specifically highlight the risk of allograft rejection when ICI are given in patients (subsequently) considered for liver transplantation.

Immunotherapy for Hepatocellular Carcinoma in the Setting of Liver Transplantation: A Review

The emerging field of immuno-oncology has brought exciting developments in the treatment of hepatocellular carcinoma (HCC). It has also raised urgent questions about the role of immunotherapy in the setting of liver transplantation, both before and after transplant. A growing body of evidence points to the safety and efficacy of immunotherapeutic agents as potential adjuncts for successful down-staging of advanced HCCs to allow successful transplant in carefully selected patients. For patients with recurrent HCC post-transplant, immunotherapy has a limited, yet growing role. In this review, we describe optimal regimens in the setting of liver transplantation.

Immunotherapy Use Prior to Liver Transplant in Patients with Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the fourth leading cause of cancer-related mortality worldwide, and its incidence has increased rapidly in the United States over the past two decades. Liver transplant is considered curative, but is not always possible, and pre-transplant immunotherapy is of great interest as a modality for downstaging the tumor burden. We present a review of the literature on pre-liver transplant immunotherapy use in patients with HCC. Our literature search queried publications in Ovid MEDLINE, Ovid Embase, and Web of Science, and ultimately identified 24 original research publications to be included for analysis. We found that the role of PD-1 and PD-L1 in risk stratification for rejection is of special interest to researchers, and ongoing randomized clinical trials PLENTY and Dulect 2020-1 will provide insight into the role of PD-1 and PD-L1 in liver transplant management in the future. This literature search and the resulting review represents the most thorough collection, analysis, and presentation of the literature on the subject to date.

Hepatocellular carcinoma downstaging for liver transplantation in the era of systemic combined therapy with anti-VEGF/TKI and immunotherapy

Hepatocellular carcinoma remains a global health challenge affecting close to 1 million cases yearly. Liver transplantation provides the best long-term outcomes for those meeting strict criteria. Efforts have been made to expand these criteria, whereas others have attempted downstaging approaches. Although locoregional approaches to downstaging are appealing and have demonstrated efficacy, limitations and challenges exists including poor imaging modality to assess response and appropriate endpoints along the process. Recent advances in systemic treatments including immune checkpoint inhibitors alone or in combination with tyrosine kinase inhibitors have prompted the discussion regarding their role for downstaging disease prior to transplantation. Here, we provide a review of prior locoregional approaches for downstaging, new systemic agents and their role for downstaging, and finally, key and critical considerations of the assessment, endpoints, and optimal designs in clinical trials to address this key question.

Immune Checkpoint Inhibitors as Therapy to Down-Stage Hepatocellular Carcinoma Prior to Liver Transplantation

Hepatocellular Carcinoma (HCC) is the most common liver malignancy and third leading cause of cancer death worldwide. For early- and intermediate-stage disease, liver-directed therapies for locoregional control, or down-staging prior to definitive surgical therapy with hepatic resection or liver transplantation, have been studied broadly, and are the mainstays of current treatment guidelines. As HCC incidence has continued to grow, and with more patients presenting with advanced disease, our current treatment modalities do not suffice, and better therapies are needed to improve disease-specific and overall survival. Until recently, sorafenib was the only systemic therapy utilized, and was associated with dismal results. The advent of immuno-oncology has been of significant interest, and has changed the paradigm of therapy for HCC. Lately, combination regimens including atezolizumab plus bevacizumab; durvalumab plus tremelimumab; and pembrolizumab plus Lenvatinib have shown impressive responses of between 25-35%; this is much higher than responses observed with single agents. Complete responses with checkpoint inhibitor therapy have been observed in advanced-stage HCC patients. These dramatic results have naturally led to several questions. Can or should checkpoint inhibitors, or other immunotherapy combinations, be used routinely before resection or transplant? Is there a synergistic effect of immunotherapy with locoregional therapy, and will pre-treatment increase disease-free survival after surgical intervention? Is it immunologically safe to use these therapies prior to transplantation? Much is still to be learned in terms of the dosing, timing, and overall utility of the use of immune checkpoint inhibitors for pre-transplant care and down-staging. More studies will be needed to understand the management of adverse events while maximizing the therapeutic window of these agents. In this review, we look at the current data on therapy with immune checkpoint inhibitors in advanced HCC, with a focus on pre-transplant treatment prior to liver transplant.