Liver Resection for Neuroendocrine Tumor Liver Metastases Within Milan Criteria for Liver Transplantation

Liver transplantation for gastroenteropancreatic neuroendocrine liver metastasis: optimal patient selection and perioperative management in the era of multimodal treatments

Gastroenteropancreatic neuroendocrine tumors (NET) often metastasize to the liver. Although curative liver resection provides a favorable prognosis for patients with neuroendocrine liver metastasis (NELM), with a 5-year survival rate of 70-80%, recurrence is almost inevitable, mainly in the remnant liver. In Western countries, liver transplantation (LT) has been performed in patients with NELM, with the objective of complete removal of macro- and micro-NELMs. However, prognosis had been unsatisfactory, with 5-year overall survival and recurrence-free survival rates of approximately 50 and 30%, respectively. In 2007, the Milan criteria were proposed as indications for LT for NELM. The criteria included: (1) confirmed histology of NET-G1 or G2; (2) a primary tumor drained by the portal system and all extrahepatic diseases removed with curative resection before LT; (3) liver involvement ≤50%; (4) good response or stable disease for at least 6 months before LT; (5) age ≤ 55 years. A subsequent report demonstrated outstanding LT outcomes for NELM within the Milan criteria, with 5-year overall survival and recurrence rates of 97 and 13%, respectively. In Japan, living donor LT (LDLT) for NELM has been performed sporadically in only 16 patients by 2021 in Japan; however, no consensus has been reached on the indications or perioperative management of LDLT. This article presents the outcomes of these 16 patients who underwent LDLT in Japan and reviews the literature to clarify optimal indications and perioperative management of LDLT for NELM in the era of novel multimodal treatments.

EASL Clinical Practice Guidelines on liver transplantation

Liver transplantation (LT) is an established life-saving procedure. The field of LT has changed in the past 10 years from several perspectives, with the expansion of indications, transplantation of patients with acute-on-chronic liver failure, evolution of transplant oncology, the use of donations after cardiac death, new surgical techniques, and prioritisation of recipients on the waiting list. In addition, the advent of organ perfusion machines, the recognition of new forms of rejection, and the attention paid to the transition from paediatric to adult patients, have all improved the management of LT recipients. The purpose of the EASL guidelines presented here is not to cover all aspects of LT but to focus on developments since the previous EASL guidelines published in 2016.

Distinct clinicopathological features of neuroendocrine liver metastases originating from the pancreas and rectum

INTRODUCTION

Survival comparisons among patients with liver metastases from pancreatic and rectal neuroendocrine tumors (NETs) were limited, and the efficacy of observation rules in patients undergoing hepatectomy for neuroendocrine liver metastases (NELMs) was unknown. This study aims to distinguish these characteristics and clarify the effects of the observation rules on NELMs.

METHODS

Clinical data were separately collected from patients with pancreatic and rectal NELMs at medical centers in both Japan and China. The Japanese cohort followed the observation rules for the resection of NELMs. A comparative analysis was conducted on clinical characteristics and prognosis features such as overall survival time (OS) and disease-free survival interval (DFS-I).

RESULTS

Enrollment included 47 and 34 patients from Japan and China, respectively. Of these, 69 and 12 patients had tumors originating from the pancreas and rectum, respectively. The OS time in patients undergoing primary tumor resection was significantly longer; however, the OS time between the patients undergoing and not undergoing radical resection of liver metastasis was the same. In asynchronous NELMs, patients with rectal (R)-NELMs showed a significantly higher proportion of type III NELMs. Additionally, the median DFS-I of asynchronous R-NELMs was longer than the recommended follow-up time, with 71.4% of them classified as G2. In the Japanese cohort, patients who adhered to the observation rules exhibited a longer median DFS after hepatectomy for NELMs compared with their counterparts.

CONCLUSION

Although curative surgery is crucial for primary lesions, personalized approaches are required to manage NELMs. Extended overall follow-ups and shortened follow-up intervals are recommended for G2 stage rectal NETs. The observation rules for NELMs require further validation with a larger sample size.

Liver transplantation as an alternative for the treatment of neuroendocrine liver metastasis: Appraisal of the current evidence

BACKGROUND

Liver transplantation (LT) for neuroendocrine liver metastases (NELM) is still in debate. Studies comparing LT with liver resection (LR) for NELM are scarce, as patient selection is heterogeneous and experience is limited. The goal of this review was to provide a critical analysis of the evidence on LT versus LR in the treatment of NELM.

DATA SOURCES

A scoping literature search on LT and LR for NELM was performed with PubMed, including English articles up to March 2023.

RESULTS

International guidelines recommend LR for NELM in resectable, well-differentiated tumors in the absence of extrahepatic metastatic disease with superior results of LR compared to systemic or liver-directed therapies. Advanced liver surgery has extended resectability criteria whilst entailing increased perioperative risk and short disease-free survival. In highly selected patients (based on the Milan criteria) with unresectable NELM, oncologic results of LT are promising. Prognostic factors include tumor biology (G1/G2) and burden, waiting time for LT, patient age and extrahepatic spread. Based on low-level evidence, LT for low-grade NELM within the Milan criteria resulted in improved disease-free survival and overall survival compared to LR. The benefits of LT were lost in patients beyond the Milan NELM-criteria.

CONCLUSIONS

With adherence to strict selection criteria especially tumor biology, LT for NELM is becoming a valuable option providing oncologic benefits compared to LR. Recent evidence suggests even stricter selection criteria with regard to tumor biology.

Transplant oncology - Current indications and strategies to advance the field

Liver transplantation (LT) was originally described by Starzl as a promising strategy to treat primary malignancies of the liver. Confronted with high recurrence rates, indications drifted towards non-oncologic liver diseases with LT finally evolving from a high-risk surgery to an almost routine surgical procedure. Continuously improving outcomes following LT and evolving oncological treatment strategies have driven renewed interest in transplant oncology. This is not only reflected by constant refinements to the criteria for LT in patients with HCC, but especially by efforts to expand indications to other primary and secondary liver malignancies. With new patient-centred oncological treatments on the rise and new technologies to expand the donor pool, the field has the chance to come full circle. In this review, we focus on the concept of transplant oncology, current indications, as well as technical and ethical aspects in the context of donor organs as precious resources.

Impact of primary tumor resection and metastasectomy among gastroentero-pancreatic neuroendocrine tumors with liver metastases only on survival

BACKGROUND

Despite recommendations for primary tumor resection (PTR) with or without liver resection (LR) in the patients with gastroenteropancreatic neuroendocrine tumors (GEP-NETs) and isolated liver metastases, there are conflicting data for their impact on overall survival (OS).

METHODS

2320 patients with GEP-NETs and isolated liver metastases were identified from NCDB. Multiple imputations were used to accommodate missing data, and inverse probability of treatment weighting (IPTW) was conducted to minimize bias.

RESULTS

Patients with PTR had a greater OS than those without PTR (3-year rate of 88.6% vs. 69.9%, P < 0.001), which was preserved in the adjusted analysis (IPTW-adjusted HR = 0.387, 95% CI: 0.264-0.567; P < 0.001). Patients with LR had a greater OS than those without LR (3-year rate 87.7% vs. 75.2%, P = 0.003), which was also preserved in adjusted analysis (IPTW-adjusted HR = 0.450, 95% CI: 0.229-0.885; P = 0.021). Patients undergoing both PTR and LR had the greatest survival advantage than those with other surgical interventions (P < 0.001).

CONCLUSIONS

Either PTR or LR is associated with improved survival for GEP-NET patients with isolated liver metastases. However, there remains significant selection bias in the current study, and caution should be exercised when selecting patients for resection.

The Role of Liver Transplantation in the Treatment of Liver Metastases from Neuroendocrine Tumors

OPINION STATEMENT

Transplant oncology is a new field of medicine referred to the use of solid organ transplantation, particularly the liver, to improve prognosis and quality of life in cancer patients. In unresectable, liver-only metastases from neuroendocrine tumors (NETs) of the digestive tract, liver transplantation represents a competitive chance of cure. Due to the limited resource of donated organs, accurate patients' selection is crucial in order to maximize transplant benefit. Several tumor- and patient-related factors should be considered. Among them, primary tumors with a low grade of differentiation (G1-G2 or Ki67 < 10%), located in a region drained by the portal system and removed before transplantation with at least 3-6 months period of disease stability observed before transplant listing, can be considered for transplantation. In case of NET located in the pancreas, extended lymphadenectomy should complement curative pancreatic resection. A number of other features are described in this review of liver transplantation for NET metastases. Comprehensive approach including various forms of non-surgical treatment and detailed planning and timing of total hepatectomy are discussed. Open issues remain on possible expansion of current criteria while maintaining the same long-term benefit demonstrated with the Milan NET criteria with respect to other non-transplant options, with particular reference to liver resection, peptide receptor radionuclide therapy, and locoregional and systemic treatments.

LIVER TRANSPLANT FOR METASTATIC NEUROENDOCRINE TUMORS: A SINGLE-CENTER REPORT

BACKGROUND

Neuroendocrine tumors are rare neoplasms of uncertain biological behavior. The liver is one of the most common sites of metastases, occurring in 50% of patients with metastatic disease.

AIMS

To analyze a clinical series in liver transplant of patients with neuroendocrine tumors metastases.

METHODS

A retrospective descriptive study, based on the review of medical records of patients undergoing liver transplants due to neuroendocrine tumor metastases in a single center in northeast Brazil, over a period of 20 years (January 2001 to December 2021).

RESULTS

During the analyzed period, 2,000 liver transplants were performed, of which 11 were indicated for liver metastases caused by neuroendocrine tumors. The mean age at diagnosis was 45.09±14.36 years (26-66 years) and 72.7% of cases were females. The most common primary tumor site was in the gastrointestinal tract in 64% of cases. Even after detailed investigation, three patients had no primary tumor site identified (27%). Overall survival after transplantation at one month was 90%, at one year was 70%, and five year, 45.4%. Disease-free survival rate was 72.7% at one year and 36.3% at five years.

CONCLUSIONS

Liver transplantation is a treatment modality with good overall survival and disease-free survival results in selected patients with unresectable liver metastases from neuroendocrine tumors. However, a rigorous selection of patients is necessary to obtain better results and the ideal time for transplant indication is still a controversial topic in the literature.

Liver Transplant for Patients With Neuroendocrine Tumor: A Report of 2 Exceptional Cases and Literature Review

Patients with neuroendocrine tumors with unresec-table liver involvement can benefit from liver transplant. There is a specific set of guidelines for neuroendocrine tumors with liver metastasis that involve less than 50% of the liver. However, beyond those guidelines, there are reports of exceptional criteria patients who benefited from liver transplant. Here, we present 2 unusual cases of patients with exceptional circumstances and with neuroendocrine tumors who underwent liver transplant. The first case describes a patient with an extremely rare neuroen-docrine tumor of the proximal common bile duct that caused liver biliary cirrhosis. The patient underwent tumor resection and liver transplant concurrently. The second case describes a patient with a neuroendocrine tumor of unknown primary origin with more than 50% hepatic involvement who received a liver transplant after downstaging. In our center, patients with unresectable hepatic metastases from neuroendoc-rine tumors are currently selected for liver transplant based on well-established criteria. However, these 2 cases did not meet the criteria for consideration of liver transplant; thus, multidisciplinary team sessions were held to discuss these 2 cases. After a period of nonsurgical treatment and evaluation of the tumor behavior, we selected the patients as candidates for liver transplant based on the favorable tumor behavior and favorable response to treatment. For both patients, we did not observe any signs of tumor recurrence during follow-up. The outcomes were acceptable, and the patients tolerated treatment well. Considering the favorable tumor pathology (G1 phase and low Ki67 index), we suggest that more studies should be conducted to evaluate the outcomes of patients with low-grade tumors and that the criteria for patients with low-grade tumors could be extended based on such future data.

Treatment strategies for neuroendocrine liver metastases: a systematic review

BACKGROUND

Gastroenteropancreatic neuroendocrine tumors are often diagnosed when metastatic. The liver is the main site of metastases. Unfortunately, optimal management of neuroendocrine liver metastases remains a topic of debate. The aim of this study was to make a systematic review of the current literature about the results of the different treatments of neuroendocrine liver metastases.

METHODS

A systematic review was conducted for English language publications from 1995 to 2021. Outcomes were analyzed according to survival, disease-free survival, and in the case of systemic therapies, progression-free survival.

RESULTS

5509 patients were analyzed in the review. 67% of patients underwent surgery achieving 5 years overall survival despite only 30% percent without a recurrence. 60% of patients that had received a transplant reached 5 years survival with a low disease-free survival rate (20%). Five-year survival rate was 36.2% for patients undergoing loco-regional therapies.

CONCLUSION

Surgical resection is the best treatment when metastases are resectable, with the highest rate of survival, although liver transplantation shows good results for patients not eligible for surgery. Loco-regional therapies may be useful when surgical resection is contraindicated, or selectively used as a bridge to surgery or transplantation. Systemic therapies are indicated in patients for whom curative treatment cannot be obtained.

Surgery, Liver Directed Therapy and Peptide Receptor Radionuclide Therapy for Pancreatic Neuroendocrine Tumor Liver Metastases

Pancreatic neuroendocrine tumors (PNETs) are described by the World Health Organization (WHO) classification by grade (1–3) and degree of differentiation. Grade 1 and 2; well differentiated PNETs are often characterized as relatively “indolent” tumors for which locoregional therapies have been shown to be effective for palliation of symptom control and prolongation of survival even in the setting of advanced disease. The treatment of liver metastases includes surgical and non-surgical modalities with varying degrees of invasiveness; efficacy; and risk. Most of these modalities have not been prospectively compared. This paper reviews literature that has been published on treatment of pancreatic neuroendocrine liver metastases using surgery; liver directed embolization and peptide receptor radionuclide therapy (PRRT). Surgery is associated with the longest survival in patients with resectable disease burden. Liver-directed (hepatic artery) therapies can sometimes convert patients with borderline disease into candidates for surgery. Among the three embolization modalities; the preponderance of data suggests chemoembolization offers superior radiographic response compared to bland embolization and radioembolization; but all have similar survival. PRRT was initially approved as salvage therapy in patients with advanced disease that was not amenable to resection or embolization; though the role of PRRT is evolving rapidly

Role of surgical treatments in high-grade or advanced gastroenteropancreatic neuroendocrine neoplasms

Over the last 40 years, the incidence and prevalence of gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) have continued to increase. Compared to other epithelial neoplasms in the same organ, GEP-NENs exhibit indolent biological behavior, resulting in more chances to undergo surgery. However, the role of surgery in high-grade or advanced GEP-NENs is still controversial. Surgery is associated with survival improvement of well-differentiated high-grade GEP-NENs, whereas poorly differentiated GEP-NENs that may benefit from resection require careful selection based on Ki67 and other tissue biomarkers. Additionally, surgery also plays an important role in locally advanced and metastatic disease. For locally advanced GEP-NENs, isolated major vascular involvement is no longer an absolute contraindication. In the setting of metastatic GEP-NENs, radical intended surgery is recommended for patients with low-grade and resectable metastases. For unresectable metastatic disease, a variety of surgical approaches, including cytoreduction of liver metastasis, liver transplantation, and surgery after neoadjuvant treatment, show survival benefits. Primary tumor resection in GEP-NENs with unresectable metastatic disease is associated with symptom control, prolonged survival, and improved sensitivity toward systemic therapies. Although there is no established neoadjuvant or adjuvant strategy, increasing attention has been given to this emerging research area. Some studies have reported that neoadjuvant therapy effectively reduces tumor burden, improves the effectiveness of subsequent surgery, and decreases surgical complications.

Liver Transplantation in Malignancies: A Comprehensive and Systematic Review on Oncological Outcome

Introduction

Liver transplantation (LT) is today's standard treatment for both end-stage liver disease and tumors; however, suitable grafts for LT are a scarce resource and outcome after LT is highly dependent on its underlying indication. Thus, patients must be carefully selected to optimize the number of life years gained per graft. This comprehensive and systematic review critically reflects the most recently published oncological outcome data after LT in malignancies based on the preoperative radiological findings.

Methods

A systematic literature search was conducted to detect preferentially most recent high-volume series or large database analysis on oncological outcomes after LT for both primary liver cancer and liver metastases between January 1, 2019, and November 14, 2020. A comprehensive review on the radiological assessment of the reviewed liver malignancies is included and its preoperative value for an outcome-driven indication reflected.

Results

Twenty most recent high-volume or relevant studies including a total number of 2,521 patients were identified including 4, 4, 4, 4, 3, and 1 publications on oncological outcome after LT for hepatocellular carcinoma, cholangiocellular carcinoma, hepatic epitheloid hemangioendothelioma, hepatoblastoma, and both metastatic neuroendocrine tumors and colorectal cancer, respectively. The overall survival is comparable to patients without tumors if patients with malignancies are well selected for LT; however, this is highly dependent on tumor entity, tumor stage, and both neoadjuvant and concomitant treatment.

Discussion/Conclusion

LT is a promising option for better survival in patients with malignant liver tumors in selected patients; however, the indication must be critically discussed prior to LT in every single case in the context of organ shortage.

Neuroendocrine liver metastases: The role of liver transplantation

PURPOSE OF REVIEW

Neuroendocrine tumor (NET) metastasis localized to the liver is an accepted indication for liver transplantation as such tumors have a low biological aggressiveness in terms of malignancy and are slow growing.

RECENT FINDINGS

The long-term results are comparable with and in some cases even better than those of transplantations performed for primary liver cancer. However, compared with nonmalignant conditions, neuroendocrine liver metastasis (NELM) may result in an inferior outcome of transplantation. In the face of the scarcity of donated organs and recent improved results of non-surgical treatment for NELM, controversy over patient selection and timing for liver transplantation continues.

SUMMARY

In this review, we provide an overview of the diagnostic work-up and selection criteria of patients with NELM being considered for liver transplantation. Thereafter, we provide a critical analysis of the reported outcomes of OLT.

Neuroendocrine liver metastases: a contemporary review of treatment strategies

Well-differentiated neuroendocrine tumors (NETs) are globally increasing in prevalence and the liver is the most common site of metastasis. Neuroendocrine liver metastases (NELM) are heterogeneous in clinical presentation and prognosis. Fortunately, recent advances in diagnostic techniques and therapeutic strategies have improved the multidisciplinary management of this challenging condition. When feasible, surgical resection of NELM offers the best long-term outcomes. General indications for hepatic resection include performance status acceptable for major liver surgery, grade 1 or 2 tumors, absence of extrahepatic disease, adequate size and function of future liver remnant, and feasibility of resecting >90% of metastases. Adjunct therapies including concomitant liver ablation are generally safe when used appropriately and may expand the number of patients eligible for surgery. Among patients with synchronous resectable NELM, resection of the primary either in a staged or combined fashion is recommended. For patients who are not surgical candidates, liver-directed therapies such as transarterial embolization, chemoembolization, and radioembolization can provide locoregional control and improve symptoms of carcinoid syndrome. Multiple systemic therapy options also exist for patients with advanced or progressive disease. Ongoing research efforts are needed to identify novel biomarkers that will define the optimal indications for and sequencing of treatments to be delivered in a personalized fashion.

Liver transplantation for unresectable malignancies: Beyond hepatocellular carcinoma

Indications for liver transplantation have expanded over the past few decades owing to improved outcomes and better understanding of underlying pathologies. In particular, there has been a growing interest in the field of transplant oncology in recent years that has led to considerable developments which have pushed the boundaries of malignant indications for liver transplantation beyond hepatocellular carcinoma (HCC). In this article, we review and summarise the published evidence for liver transplantation in non-HCC primary and metastatic liver malignancies and highlight ongoing clinical trials that address unresolved questions therein. We also examine the current technical, immunological and oncological challenges that face liver transplantation in this growing field and explore potential approaches to overcome these barriers.

Liver transplantation in patients with liver metastases from neuroendocrine tumors

The prevalence of metastatic disease in neuroendocrine tumors (NETs) is very high (60-80%) and cancer-related death among these patients is generally due to metastatic disease. Numerous treatment options for cure and disease control have been investigated for patients with neuroendocrine liver metastases (NELM). Despite the success of liver directed therapy on slowing tumor progression and palliating symptoms, the chance of being cured by liver resection is 40-50% and only roughly 20% of patients have potentially resectable disease. As such, there has been interest in liver transplantation (LT) as a potentially curative option for patients with unresectable disease. Several criteria have been proposed in order to balance long-term outcomes of patients with NELM and the problem of organ shortage including the Milan-NET criteria, the UNOS criteria and the ENETS guidelines. In the most representative studies, recurrence rate after LT has ranged from 30% to 60% with a 5-year OS ranging from 50% to 97%. This large variability is due to the retrospective nature of the studies available, which used different inclusion criteria. As such, outcomes and the prognostic factors associated with LT for NELM warrant further investigation.