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.

Dose-effect relationships in neuroendocrine tumour liver metastases treated with [166Ho]-radioembolization

PURPOSE

Aim of this study was to investigate a dose-response relationship, dose-toxicity relationship, progression free survival (PFS) and overall survival (OS) in neuroendocrine tumour liver metastases (NELM) treated with holmium-166-microspheres radioembolization ([166Ho]-radioembolization).

MATERIALS AND METHODS

Single center, retrospective study included patients with NELM that received [166Ho]-radioembolization with post-treatment SPECT/CT and CECT or MRI imaging for 3 months follow-up. Post-treatment SPECT/CT was used to calculate tumour (Dt) and whole liver healthy tissue (Dh) absorbed dose. Clinical and laboratory toxicity was graded by Common Terminology Criteria for Adverse Events (CTCAE), version 5 at baseline and three-months follow-up. Response was determined according to RECIST 1.1. The tumour and healthy doses was correlated to lesion-based objective response and patient-based toxicity. Kaplan Meier analyses were performed for progression free survival (PFS) and overall survival (OS).

RESULTS

Twenty-seven treatments in 25 patients were included, with a total of 114 tumours. Median follow-up was 14 months (3 - 82 months). Mean Dt in non-responders was 68 Gy versus 118 Gy in responders, p = 0.01. ROC analysis determined 86 Gy to have the highest sensitivity and specificity, resp. 83% and 81%. Achieving a Dt of ≥ 120 Gy provided the highest likelihood of response (90%) for obtaining response. Sixteen patients had grade 1-2 clinical toxicity and only one patient grade 3. No clear healthy liver dose-toxicity relationship was found. The median PFS was 15 months (95% CI [10.2;19.8]) and median OS was not reached.

CONCLUSION

This study confirms the safety and efficacy of [166Ho]-radioembolization in NELM in a real-world setting. A clear dose-response relationship was demonstrated and future studies should aim at a Dt of ≥ 120 Gy, being predictive of response. No dose-toxicity relationship could be established.

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.

Where Are We Now with Liver Transplantation in Neuroendocrine Neoplasms? The Place of Liver Transplantation for Grades 1 and 2 Well-Differentiated Unresectable Liver Metastatic Neuroendocrine Tumours

PURPOSE OF REVIEW

This review outlines the role of liver transplantation in selected patients with unresectable neuroendocrine tumour liver metastases. It discusses the international consensus on eligibility criteria and outlines the efforts taking place in the UK and Ireland to develop effective national liver transplant programmes for neuroendocrine tumour patients.

RECENT FINDINGS

In the early history of liver transplantation, indications included cancer metastases to the liver as well as primaries of liver origin. Often, liver transplantation was a salvage procedure. The early results were disappointing, including in patients with neuroendocrine tumours. These data discouraged the widespread adoption of liver transplantation for neuroendocrine tumour liver metastases (NET LM). A few centres persisted in performing liver transplantation for patients with NET LM and in determining parameters predictive of good outcomes. Their work has provided evidence for benefit of liver transplantation in a selected group of patients with NET LM. Liver transplantation for NET LM is now accepted as a valid indication by many professional bodies, including the European Neuroendocrine Tumour Society (ENETS) and the United Network for Organ Sharing (UNOS). It is nevertheless rarely utilised. The UK and the Republic of Ireland are commencing a pilot programme of liver transplantation in selected patients. This programme will help develop the expertise and infrastructure to make liver transplantation for NET LM a routine procedure.

Dynamic Contrast-enhanced CT to Evaluate Early Response in Neuroendocrine Liver Metastases Treated With Everolimus and Radiation

BACKGROUND/AIM

The optimal method to evaluate response of neuroendocrine liver metastases (NELM) to radiation treatment (RT) is unknown; tumor perfusion parameters were evaluated by using dynamic contrast-enhanced computed tomography (DCE-CT) to correlate with efficacy in a prospective pilot study utilizing everolimus with radiotherapy for NELM.

PATIENTS AND METHODS

Fourteen patients with progressive NELM received everolimus for 28 days prior to, concurrent with, and 14 days following radiation. Patients had a DCE-CT at baseline (t0), prior to radiation (t1) and 7 days after radiation (t2). Per lesion response was evaluated per standard response evaluation criteria (RECIST v1.1). Median statistics of the perfusion parameters were tabulated and included: blood flow (BF), blood volume (BV), and permeability (PS). Correlations between the parameters and the maximum percent change in size of the NELM at 12-months were explored. NELM not treated with radiation served as an internal control.

RESULTS

Twenty-one treated NELM in 10 patients were evaluable. Compared to t0, BV increased at t1 (median 11%, range -15 to +37%, p=0.59), and then decreased significantly at t2 (median -8.4%, range -29 to +5.4%, p<0.03). A trend of increased BV in internal controls at each time point supports that the observed effect is due to radiation. Conventional objective response rate was 33%; no progression was seen within 12-months.

CONCLUSION

Changes in DCE-CT were observed in patients receiving everolimus and radiation for NELM, with BV decreasing significantly following radiotherapy. Given the challenges in assessing response in NELM using traditional response evaluation criteria in any context, DCE-CT appears to be a promising modality.

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.

Is Resection of Primary Midgut Neuroendocrine Tumors in Patients with Unresectable Metastatic Liver Disease Justified? A Systematic Review and Meta-Analysis

INTRODUCTION

Patients with midgut neuroendocrine tumors (MNETs) frequently present with metastatic disease at the time of diagnosis. Although combined resection of the primary MNET and liver metastases (NELM) is usually recommended for appropriate surgical candidates, primary tumor resection (PTR) in the setting of extensive, inoperable metastatic disease remains controversial.

METHODS

A systematic review was performed according to PRISMA guidelines utilizing Medline (PubMed), Embase, and Cochrane library-Cochrane Central Register of Controlled Trials (CENTRAL) databases until September 30, 2018.

RESULTS

Among patients with MNET and NELM, 1226 (68.4%; range, 35.5-85.1% per study) underwent PTR, whereas 567 (31.6%; range, 14.9-64.5%) patients did not. Median follow-up ranged from 55 to 90 months. Cytoreductive liver surgery was performed in approximately 15.7% (range, 0-34.8%) of patients. Pooled 5-year overall survival (OS) among the resected group was approximately 73.1% (range, 57-81%) versus 36.6% (range, 21-46%) for the non-resection group. For patients without liver debulking surgery, PTR remained associated with a decreased risk of death at 5 years compared with patients who did not have the primary tumor resected (HR 0.36, 95% CI 0.16 to 0.79, p = 0.01; I² 58%, p = 0.12). For patients undergoing PTR, 30-day postoperative mortality ranged from 1.43 to 2%.

CONCLUSION

PTR was safe with a low peri-operative risk of mortality and was associated with an improved OS for patients with MNET and unresectable NELM. Given the poor quality of evidence, however, strong evidenced-based recommendations cannot be made based on these retrospective single center-derived data. Future well-design randomized controlled trials will be critical in elucidating the optimal treatment strategies for patients with MNET and advanced metastatic disease.

Risk of Infectious Complications After Simultaneous Gastrointestinal and Liver Resections for Neuroendocrine Tumor Metastases

BACKGROUND

Neuroendocrine tumors (NETs) are a relatively rare category of cancers that arise in the gastrointestinal (GI) tract and other organs. Extended hepatectomies including resection of multiple organs are often necessary to achieve negative margins.

METHODS

We performed a review of patients undergoing liver resection for NET liver metastases from 2005 to 2015 using National Surgical Quality Improvement Program. We compared patients undergoing hepatectomy alone (HA) versus hepatectomy and a concomitant GI surgery procedure (colorectal, small bowel, and pancreatic) to evaluate postoperative infectious complications.

RESULTS

During the study period, 354 patients underwent liver resection for metastatic NET. Hepatectomy alone was performed in 98 patients, and concomitant GI surgery was performed in 256 patients, including 83 colorectal resections (HCCR), 68 small bowel resections, 75 distal pancreatectomies, and 35 pancreaticoduodenectomies (HCPD). Infectious complications were more likely to occur in those undergoing HCPD (60%, P < 0.001), and HCCR (32.5%, P < 0.05) than in those undergoing HA (16.3%). Patients undergoing HCPD and HCCR had a 7.69-fold and 2.52-fold increased risk of infectious complication, respectively, compared with HA after adjustment for other infection risk factors.

CONCLUSIONS

Neuroendocrine liver metastases requiring liver resection with concomitant colorectal resection or pancreaticoduodenectomy are at significantly increased risk of developing infectious complications.

Morphological and Functional Imaging for Detecting and Assessing the Resectability of Neuroendocrine Liver Metastases

This review evaluates the diagnostic efficacy of different morphological and functional imaging modalities (ultrasound [US], computed tomography [CT], magnetic resonance [MR] imaging, scintigraphy, and positron emission tomography [PET]) in detecting neuroendocrine liver metastases (NELM), assessing vascular and biliary involvement, and the presence of extrahepatic disease. MR imaging is superior for depicting NELM compared to US, CT, and somatostatin receptor scintigraphy. Diffusion-weighted MR imaging is more sensitive for detecting NELM than both T2-weighted and dynamic gadolinium-enhanced MR sequences, and should be systematically performed. Similarly, gadoxetic acid-enhanced MR imaging is more sensitive for detecting liver metastases than conventional extracellular gadolinium chelate-enhanced MR sequences. Its role in detecting NELM remains investigational but appears promising. Somatostatin receptor-targeted PET/CT is a highly effective approach in assessing the resectability of well-differentiated NELM due to very high specificity (and high sensitivity) and its ability to detect small volume extrahepatic disease; this molecular imaging modality is becoming increasingly available in and outside Europe after the recent approval of 6868-DOTATATE in the US. In addition, the information from multiphase, contrast-enhanced CT with 3D reconstruction - obtained concurrently with the information on somatostatin receptor expression of the metastases - is very helpful in planning the extent and type of resection of NELM.

Nonfunctional pancreatic neuroendocrine tumors

Pancreatic neuroendocrine tumors are a group of rare, heterogeneous neoplasms that have been increasing in incidence the past few decades largely because of the diagnosis of pancreatic incidentalomas on cross-sectional imaging. Although these tumors are classically associated with clinical syndromes that result from excess secretion of particular hormones, most pancreatic neuroendocrine tumors are nonfunctional tumors presenting with symptoms secondary to mass effect, metastatic disease, or as incidental findings. This article reviews the diagnostic algorithm, surgical management, and available systemic therapies for nonfunctional pancreatic neuroendocrine tumors.