Treatment of Liver Metastases from Midgut Neuroendocrine Tumours: A Systematic Review and Meta-Analysis

Current Management of Neuroendocrine Tumour Liver Metastases

PURPOSE OF REVIEW

This article aims to illustrate the current state of investigations and management of liver metastases in patients with Neuroendocrine Neoplasms. Neuroendocrine tumours (NETs) are rising in incidence globally and have become the second most prevalent gastrointestinal malignancy in UK and USA. Frequently, patients have metastatic disease at time of presentation. The liver is the most common site of metastases for gastro-enteropancreatic NETs. Characterisation of liver metastases with imaging is important to ensure disease is not under-staged.

RECENT FINDINGS

Magnetic resonance imaging and positron emission tomography are now becoming standard of care for imaging liver metastases. There is an increasing armamentarium of therapies available for management of NETs and loco-regional therapy for liver metastases. The data supporting surgical and loco-regional therapy is reviewed with focus on role of liver transplantation. It is important to use appropriate imaging and classification of NET liver metastases. It is key that decisions regarding approach to treatment is undertaken in a multidisciplinary team and that individualised approaches are considered for management of patients with metastatic NETs.

Transarterial (chemo)embolisation versus systemic chemotherapy for colorectal cancer liver metastases

BACKGROUND

The liver is affected by two groups of malignant tumours: primary liver cancers and liver metastases. Liver metastases are significantly more common than primary liver cancer, and five-year survival after radical surgical treatment of liver metastases ranges from 28% to 50%, depending on primary cancer site. However, R0 resection (resection for cure) is not feasible in most people; therefore, other treatments have to be considered in the case of non-resectability. One possible option is based on the concept that the blood supply to hepatic tumours originates predominantly from the hepatic artery. Transarterial chemoembolisation (TACE) of the peripheral branches of the hepatic artery can be achieved by administering a chemotherapeutic drug followed by vascular occlusive agents and can lead to selective necrosis of the cancer tissue while leaving normal liver parenchyma virtually unaffected. The entire procedure can be performed without infusion of chemotherapy and is then called bland transarterial embolisation (TAE). These procedures are usually applied over a few sessions. Another possible treatment option is systemic chemotherapy which, in the case of colorectal cancer metastases, is most commonly performed using FOLFOX (folinic acid, 5-fluorouracil, and oxaliplatin) and FOLFIRI (folinic acid, 5-fluorouracil, and irinotecan) regimens applied in multiple sessions over a long period of time. These therapies disrupt the cell cycle, leading to death of rapidly dividing malignant cells. Current guidelines determine the role of TAE and TACE as non-curative treatment options applicable in people with liver-only or liver-dominant metastatic disease that is unresectable or non-ablatable, and in people who have failed systemic chemotherapy. Regarding the treatment modalities in people with colorectal cancer liver metastases, we found no systematic reviews comparing the efficacy of TAE or TACE versus systemic chemotherapy.

OBJECTIVES

To evaluate the beneficial and harmful effects of transarterial embolisation (TAE) or transarterial chemoembolisation (TACE) compared with systemic chemotherapy in people with liver-dominant unresectable colorectal cancer liver metastases.

SEARCH METHODS

We searched the Cochrane Hepato-Biliary Group Controlled Trials Register, CENTRAL, MEDLINE, Embase, and three additional databases up to 4 April 2024. We also searched two trials registers and the European Medicines Agency database and checked reference lists of retrieved publications.

SELECTION CRITERIA

We included randomised clinical trials assessing beneficial and harmful effects of TAE or TACE versus systemic chemotherapy in adults (aged 18 years or older) with colorectal cancer liver metastases.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our primary outcomes were all-cause mortality; overall survival (time to mortality); and any adverse events or complications. Our secondary outcomes were cancer mortality; health-related quality of life; progression-free survival; proportion of participants dying or surviving with progression of the disease; time to progression of liver metastases; recurrence of liver metastases; and tumour response measures (complete response, partial response, stable disease, and progressive disease). For the purpose of the review and to perform necessary analyses, whenever possible, we converted survival rates to mortality rates, as this was our primary outcome. For the analysis of dichotomous outcomes, we used the risk ratio (RR); for continuous outcomes, we used the mean difference; and for time to event outcomes, we calculated hazard ratios (HRs), all with 95% confidence intervals (CI). We used the standardised mean difference with 95% CIs when the trials used different instruments. We used GRADE to assess the certainty of evidence for each outcome. We based our conclusions on outcomes analysed at the longest follow-up.

MAIN RESULTS

We included three trials with 118 participants randomised to TACE versus 120 participants to systemic chemotherapy. Four participants were excluded; one due to disease progression prior to treatment and three due to decline in health. The trials reported data on one or more outcomes. Two trials were performed in China and one in Italy. The trials differed in terms of embolisation techniques and chemotherapeutic agents. Follow-up ranged from 12 months to 50 months. TACE may reduce mortality at longest follow-up (RR 0.86, 95% CI 0.79 to 0.94; 3 trials, 234 participants; very low-certainty evidence), but the evidence is very uncertain. TACE may have little to no effect on overall survival (time to mortality) (HR 0.61, 95% CI 0.37 to 1.01; 1 trial, 70 participants; very low-certainty evidence), any adverse events or complications (3 trials, 234 participants; very low-certainty evidence), health-related quality of life (2 trials, 154 participants; very low-certainty evidence), progression-free survival (1 trial, 70 participants; very low-certainty evidence), and tumour response measures (presented as the overall response rate) (RR 1.81, 95% CI 1.11 to 2.96; 3 trials, 234 participants; very low-certainty evidence), but the evidence is very uncertain. No trials reported cancer mortality, proportion of participants dying or surviving with progression of the disease, and recurrence of liver metastases. We found no trials comparing the effects of TAE versus systemic chemotherapy in people with colorectal cancer liver metastases.

AUTHORS' CONCLUSIONS

The evidence regarding effectiveness of TACE versus systemic chemotherapy in people with colorectal cancer liver metastases is of very low certainty and is based on three trials. Our confidence in the results is limited due to the risk of bias, inconsistency, indirectness, and imprecision. It is very uncertain whether TACE confers benefits with regard to reduction in mortality, overall survival (time to mortality), reduction in adverse events or complications, improvement in health-related quality of life, improvement in progression-free survival, and tumour response measures (presented as the overall response rate). Data on cancer mortality, proportion of participants dying or surviving with progression of the disease, and recurrence of liver metastases are lacking. We found no trials assessing TAE versus systemic chemotherapy. More randomised clinical trials are needed to strengthen the body of evidence and provide insight into the benefits and harms of TACE or TAE in comparison with systemic chemotherapy in people with liver metastases from colorectal cancer.

Surgery for advanced neuroendocrine tumours of the small bowel: recommendations based on a consensus meeting of the European Society of Endocrine Surgeons (ESES)

BACKGROUND

Small bowel neuroendocrine tumours often present with locally advanced or metastatic disease. The aim of this paper is to provide evidence-based recommendations regarding (controversial) topics in the surgical management of advanced small bowel neuroendocrine tumours.

METHODS

A working group of experts was formed by the European Society of Endocrine Surgeons. The group addressed 11 clinically relevant questions regarding surgery for advanced disease, including the benefit of primary tumour resection, the role of cytoreduction, the extent of lymph node clearance, and the management of an unknown primary tumour. A systematic literature search was performed in MEDLINE to identify papers addressing the research questions. Final recommendations were presented and voted upon by European Society of Endocrine Surgeons members at the European Society of Endocrine Surgeons Conference in Mainz in 2023.

RESULTS

The literature review yielded 1223 papers, of which 84 were included. There were no randomized controlled trials to address any of the research questions and therefore conclusions were based on the available case series, cohort studies, and systematic reviews/meta-analyses of the available non-randomized studies. The proposed recommendations were scored by 38-51 members and rated 'strongly agree' or 'agree' by 64-96% of participants.

CONCLUSION

This paper provides recommendations based on the best available evidence and expert opinion on the surgical management of locally advanced and metastatic small bowel neuroendocrine tumours.

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.

Evolution of Liver Transplantation Indications: Expanding Horizons

Liver transplantation (LT) has significantly transformed the prognosis of patients with end-stage liver disease and hepatocellular carcinoma (HCC). The traditional epidemiology of liver diseases has undergone a remarkable shift in indications for LT, marked by a decline in viral hepatitis and an increase in metabolic dysfunction-associated steatotic liver disease (MASLD), along with expanded indications for HCC. Recent advancements in surgical techniques, organ preservation and post-transplant patients' management have opened new possibilities for LT. Conditions that were historically considered absolute contraindications have emerged as potential new indications, demonstrating promising results in terms of patient survival. While these expanding indications provide newfound hope, the ethical dilemma of organ scarcity persists. Addressing this requires careful consideration and international collaboration to ensure equitable access to LT. Multidisciplinary approaches and ongoing research efforts are crucial to navigate the evolving landscape of LT. This review aims to offer a current overview of the primary emerging indications for LT, focusing on acute-on-chronic liver failure (ACLF), acute alcoholic hepatitis (AH), intrahepatic and perihilar cholangiocarcinoma (i- and p-CCA), colorectal liver metastasis (CRLM), and neuroendocrine tumor (NET) liver metastases.

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.

Role of Radioembolization in Metastatic Neuroendocrine Tumors

The liver is the most common site of metastasis for neuroendocrine tumors originating from the gastrointestinal tract. Neuroendocrine liver metastases (NELMs) portend a worsening clinical course, making local management important. Local treatment options include surgery, thermal ablation, and trans-catheter intra-arterial therapies, such as radioembolization. Radioembolization is generally preferred over other embolotherapies in patients with colonized biliary systems. Current best practice involves personalized treatment planning, optimizing tumor radiation absorbed dose and minimizing radiation to the normal hepatic parenchyma. As part of a multidisciplinary approach, radioembolization is a versatile embolotherapy offering neoadjuvant, palliative, and ablative treatment options for patients with NELMs.

A Nomogram to Predict Individual Survival of Patients with Liver-Limited Metastases from Gastroenteropancreatic Neuroendocrine Neoplasms: A US Population-Based Cohort Analysis and Chinese Multicenter Cohort Validation Study

INTRODUCTION

Although gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) with liver metastasis encompass a wide variety of clinical conditions with various prognosis, no statistical model for predicting the prognosis of these patients has been established. We sought to establish a more elaborative and individualized nomogram to predict survival of patients with liver-limited metastatic GEP-NENs. In addition, this nomogram was validated by both the Surveillance, Epidemiology, and End Results (SEER) database and a Chinese multicenter cohort.

METHODS

Patients diagnosed with GEP-NENs with liver-limited metastasis between 2010 and 2016 were identified from the SEER database. Kaplan-Meier survival analysis was performed to analyze survival outcomes. A nomogram was established based on the independent prognostic variables identified from univariate and multivariate Cox regression analyses. The nomogram was evaluated in both an internal validation SEER dataset and an external validation dataset composed of patients from the Chinese multicenter cohort.

RESULTS

A total of 1,474 patients from the SEER database and 192 patients from the multicenter cohort were included. Age, tumor size, differentiation, primary tumor resection, and liver metastasis resection were identified as independent prognostic factors by univariate and multivariate Cox analyses and were verified by Kaplan-Meier survival analysis (all p < 0.0001). A nomogram was developed and validated by calibration curves and areas under the curve of the external validation cohort, which showed good consistency and veracity in predicting overall survival.

CONCLUSION

A nomogram was developed for the first time to predict the survival of patients with liver-limited metastases from GEP-NENs. Both internal and external validation demonstrated excellent discrimination and calibration of our nomogram. Based on this prognostic model, clinicians could develop more personalized treatment strategies and surveillance protocols.

Postoperative morbidity and mortality after surgical resection of small bowel neuroendocrine neoplasms: A systematic review and meta-analysis

Although small bowel resection is generally considered a low risk gastrointestinal procedure, this might not be true for small bowel neuroendocrine neoplasms (SB-NEN) as a result of potential central mesenteric involvement. We aimed to determine the reported morbidity and mortality after resection of SB-NEN in the literature and assess the effect of hospital volume on postoperative morbidity and mortality. A systematic review was performed by searching MEDLINE and Embase in March 2021. All studies reporting morbidity and/or mortality after SB-NEN resection were included. Pooled proportions of overall morbidity (Clavien-Dindo I-IV), severe morbidity (Clavien-Dindo III-IV), 30-day mortality, 90-day mortality and in-hospital mortality were calculated, as well as the association with hospital volume (high volume defined as the fourth quartile). Thirteen studies were included, with a total of 1087 patients. Pooled proportions revealed an overall morbidity of 13% (95% confidence interval [CI] = 7%-24%, I²  = 90%), severe morbidity of 7% (95% CI = 4%-14%, I²  = 70%), 30-day mortality of 2% (95% CI = 1%-3%, I²  = 0%), 90-day mortality of2% (95% CI = 2%-4%, I²  = 35%) and in-hospital mortality of 1% (95% CI = 0%-2%, I²  = 0%). An annual hospital volume of nine or more resections was associated with lower overall and severe morbidity compared to lower volume: 10% vs 15% and 4% vs 9%, respectively. Thirty-day mortality was similar (2% vs 1%) and 90-day mortality was higher in high-volume hospitals: 4% vs 1%. This systematic review with meta-analyses showed severe morbidity of 7% and low mortality rates after resection of SB-NEN. The currently available literature suggests a certain impact of hospital volume on postoperative outcomes, although heterogeneity among the included studies constrains interpretation.

Update on Incidence, Prevalence, Treatment and Survival of Patients with Small Bowel Neuroendocrine Neoplasms in the Netherlands

BACKGROUND

Small bowel neuroendocrine neoplasms (SB-NEN) are rare cancers, population-based studies are needed to study this rare indolent disease. The aim of this study was to explore trends in epidemiology, treatment and survival outcomes of patients with SB-NEN based on Dutch nationwide data.

PATIENTS AND METHODS

Patients with grade 1 or 2 SB-NEN diagnosed between 2005 and 2015 were retrieved from the Netherlands Cancer Registry and linked to The Nationwide Network and Registry of Histo- and Cytopathology in the Netherlands. Age-adjusted incidence rates were calculated based using the direct standardization method. Survival analyses were performed with the Kaplan-Meier method.

RESULTS

A total of 1132 patients were included for epidemiological analyses. The age-adjusted incidence rate of SB-NEN increased from 0.52 to 0.81 per 100.000 person-years between 2005 and 2015. Incidence was higher for males than females (0.93 vs. 0.69 in 2015). Most patients had grade 1 tumours (83%). Surgery was performed in 86% of patients, with resection of the primary tumour in 99%. During the study period, administration of somatostatin analogues (SSAs) increased from 5 to 22% for stage III and from 27 to 63% for stage IV disease. Mean follow-up was 61 (standard deviation 38) months. Survival data were complete for 975/1132 patients and five-year overall survival was 75% for stage I-II, 75% for stage III and 57% for stage IV.

CONCLUSIONS

This study shows an increase in the incidence of SB-NEN in the Netherlands. A predominant role of surgery was found in all disease stages. Use of SSAs has increased over time.

Evaluating Nationwide Application of Minimally Invasive Surgery for Treatment of Small Bowel Neuroendocrine Neoplasms

Aim

Open resection of small bowel neuroendocrine neoplasms (SB-NEN) is still considered standard-of-care, mainly because of frequently encountered multifocality and central mesenteric masses. The aim of this study was to evaluate surgical approach for SB-NEN at a national level and determine predictors for overall survival.

Methods

Patients with SB-NEN who underwent resection between 2005 and 2015 were included from the Netherlands Cancer Registry. Patient and tumor characteristics were compared between laparoscopic and open approach. Overall survival was assessed by Kaplan–Meier and compared with the Log-rank test. Independent predictors were determined by Cox proportional hazards model.

Results

In total, 482 patients were included, of whom 342 (71%) underwent open and 140 (29%) laparoscopic resection. The open resection group had significantly more multifocal tumors resected (24% vs. 14%), pN2 lymph nodes (18% vs. 7%) and stage IV disease (36% vs. 22%). Overall survival after open resection was significantly shorter compared to laparoscopic resection (3-year: 81% vs. 89%, 5-year: 71% vs. 84%, p = 0.004). In multivariable analysis, age above 60-years (60–75, HR 3.38 (95% CI 1.84–6.23); > 75 years, HR 7.63 (95% CI 3.86–15.07)), stage IV disease (HR 1.86 (95% CI 1.18–2.94)) and a laparoscopic approach (HR 0.51 (95% CI 0.28–0.94)) were independently associated with overall survival, whereas multifocal primary tumor, grade and resection margin status were not.

Conclusion

Laparoscopic resection was the approach in 29% of SB-NEN at a national level with selection of the more favorable patients. Laparoscopic resection remained independently associated with better overall survival besides age and stage, but residual confounding cannot be excluded.

Electrocoagulation for liver metastases

BACKGROUND

Primary liver tumours and liver metastases from colorectal carcinoma are two of the most common malignant tumours to affect the liver. The liver is second only to the lymph nodes as the most common site for metastatic disease. More than half of the people with metastatic liver disease will die from metastatic complications. Electrocoagulation by diathermy is a method used to destroy tumour tissue, using a high-frequency electric current generating high temperatures, applied locally with an electrode (needle, blade, or ball). The objective of this method is to destroy the tumour completely, if possible, in a single session. With the time, electrocoagulation by diathermy has been replaced by other techniques, but the evidence is unclear.

OBJECTIVES

To assess the beneficial and harmful effects of electrocoagulation by diathermy, administered alone or with another intervention, versus no intervention, other ablation methods, or systemic treatments in people with liver metastases.

SEARCH METHODS

We searched the Cochrane Hepato-Biliary Group Controlled Trials Register, CENTRAL, MEDLINE Ovid, Embase Ovid, LILACS, Science Citation Index Expanded, Conference Proceedings Citation Index - Science, CINAHL, ClinicalTrials.gov, ICTRP, and FDA to October 2020.

SELECTION CRITERIA

We considered all randomised trials that assessed beneficial and harmful effects of electrocoagulation by diathermy, administered alone or with another intervention, versus comparators, in people with liver metastases, regardless of the location of the primary tumour.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. We assessed risk of bias of the included trial using predefined risk of bias domains, and presented the review results incorporating the certainty of the evidence using GRADE.

MAIN RESULTS

We included one randomised clinical trial with 306 participants (175 males; 131 females) who had undergone resection of the sigmoid colon, and who had five or more visible and palpable hepatic metastases. The diagnosis was confirmed by histological assessment (biopsy) and by carcinoembryonic antigen (CEA) level. The trial was conducted in Iraq. The age of participants ranged between 38 and 79 years. The participants were randomised to four different study groups. The liver metastases were biopsied and treated (only once) in three of the groups: 75 received electrocoagulation by diathermy alone, 76 received electrocoagulation plus allopurinol, 78 received electrocoagulation plus dimethyl sulphoxide. In the fourth intervention group, 77 participants functioning as controls received a vehicle solution of allopurinol 5 mL 4 x a day by mouth; the metastases were left untouched. The status of the liver and lungs was followed by ultrasound investigations, without the use of a contrast agent. Participants were followed for five years. The analyses are based on per-protocol data only analysing 223 participants. We judged the trial to be at high risk of bias. After excluding 'nonevaluable patients', the groups seemed comparable for baseline characteristics. Mortality due to disease spread at five-year follow-up was 98% in the electrocoagulation group (57/58 evaluable people); 87% in the electrocoagulation plus allopurinol group (46/53 evaluable people); 86% in the electrocoagulation plus dimethyl sulphoxide group (49/57 evaluable people); and 100% in the control group (55/55 evaluable people). We observed no difference in mortality between the electrocoagulation alone group versus the control group (risk ratio (RR) 0.98, 95% confidence interval (CI) 0.94 to 1.03; 113 participants; very low-certainty evidence). We observed lower mortality in the electrocoagulation combined with allopurinol or dimethyl sulphoxide group versus the control group (RR 0.87, 95% CI 0.80 to 0.95; 165 participants; low-certainty evidence). We are very uncertain regarding post-operative deaths between the electrocoagulation alone group versus the control group (RR 1.03, 95% CI 0.07 to 16.12; 152 participants; very low-certainty evidence) and between the electrocoagulation combined with allopurinol or dimethyl sulphoxide groups versus the control group (RR 1.00, 95% CI 0.09 to 10.86; 231 participants; very low-certainty evidence). The trial authors did not report data on number of participants with other adverse events and complications, recurrence of liver metastases, time to progression of liver metastases, tumour response measures, and health-related quality of life. Data on failure to clear liver metastases were not provided for the control group. There was no information on funding or conflict of interest. We identified no ongoing trials.

AUTHORS' CONCLUSIONS

The evidence on the beneficial and harmful effects of electrocoagulation alone or in combination with allopurinol or dimethyl sulphoxide in people with liver metastases is insufficient, as it is based on one randomised clinical trial at low to very low certainty. It is very uncertain if there is a difference in all-cause mortality and post-operative mortality between electrocoagulation alone versus control. It is also uncertain if electrocoagulation in combination with allopurinol or dimethyl sulphoxide may result in a slight reduction of all-cause mortality in comparison with a vehicle solution of allopurinol (control). It is very uncertain if there is a difference in post-operative mortality between the electrocoagulation combined with allopurinol or dimethyl sulphoxide group versus control. Data on other adverse events and complications, failure to clear liver metastases or recurrence of liver metastases, time to progression of liver metastases, tumour response measures, and health-related quality of life were most lacking or insufficiently reported for analysis. Electrocoagulation by diathermy is no longer used in the described way, and this may explain the lack of further trials.

Currently available treatment options for neuroendocrine liver metastases

Neuroendocrine neoplasms (NEN) are frequently characterized by a high propensity for metastasis to the liver, which appears to be a dominant site of distant-stage disease, affecting quality of life and overall survival. Liver surgery with the intention to cure is the treatment of choice for resectable neuroendocrine liver metastases (NELM), aiming to potentially prolong survival and ameliorate hormonal symptoms refractory to medical control. Surgical resection is indicated for patients with NELM from well-differentiated NEN, while its feasibility and complexity are largely dictated by the degree of liver involvement. As a result of advances in surgical techniques over the past decades, complex 1- and 2-stage, or repeat liver resections are performed safely and effectively by experienced surgeons. Furthermore, liver transplantation for the treatment of NELM should be anchored in a multimodal and multidisciplinary therapeutic strategy and restricted only to highly selected individual cases. A broad spectrum of interventional radiology treatments for NELM have recently been available, with expanding indications that are more applicable, as they are less limited by patient- and tumor-related parameters, being therefore important adjuncts or alternatives to surgery. Overall, liver-targeted treatment modalities may precede the administration of systemic molecular targeted agents and chemotherapy for patients with liver-dominant metastatic disease; these appear to be a crucial component of multimodal management of patients with NEN. In the present review, we discuss surgical and non-surgical liver-targeted treatment approaches for NELM, each complementing the other, with a view to assisting physicians in optimizing multimodal NEN patient care.

Surgical Management of Neuroendocrine Tumor Liver Metastases

Patients with neuroendocrine tumor liver metastases (NETLMs) may develop carcinoid syndrome, carcinoid heart disease, or other symptoms from overproduction of hormones. Hepatic resection and cytoreduction is the most direct treatment of NETLMs in eligible patients, and cytoreduction improves symptoms, may reduce the sequelae of carcinoid syndrome, and extends survival. Parenchymal-sparing procedures, such as ablation and enucleation, should be considered during cytoreduction to maximize treatment of multifocal tumors while preserving healthy liver tissue. For patients with large hepatic tumor burdens, high-grade disease, or comorbidities precluding surgery, liver-directed and systemic therapies can be used to palliate symptoms and improve progression-free survival.

Liver Embolisation for Patients with Neuroendocrine Neoplasms: Systematic Review

BACKGROUND

Liver embolisation is one of the treatment options available for patients diagnosed with neuro-endocrine neoplasms (NEN). It is still uncertain whether the benefits of the various types of embolisation treatments truly outweigh the complications in NENs. This systematic review assesses the available data relating to liver embolisation in patients with NENs.

METHODS

Eligible studies (identified using MEDLINE-PubMed) were those reporting data on NEN patients who had undergone any type of liver embolisation. The primary end points were best radiological response and symptomatic response; secondary end-points included progression-free survival (PFS), overall survival (OS) and toxicity.

RESULTS

Of 598 studies screened, 101 were eligible: 16 were prospective (15.8%). The eligible studies included a total of 5,545 NEN patients, with a median of 39 patients per study (range 5-214). Pooled rate of partial response was 36.6% (38.9% achieved stable disease) and 55.2% of patients had a symptomatic response to therapy when pooled data were analysed. The median PFS and OS were 18.4 months (95% CI 15.5-21.2) and 40.7 months (95% CI 35.2-46.2) respectively. The most common toxicities were found to be abdominal pain (48.8%) and nausea (48.1%). Outcome did not significantly vary depending on the type of embolisation performed.

CONCLUSION

Liver embolisation provides adequate symptom relief for patients with carcinoid syndrome and is also able to reach partial response in a significant proportion of patients and a reasonable PFS. Quality of studies was limited, highlighting the need of further prospective studies to confirm the most suitable form of liver embolisation in NENs.

Recent developments and ongoing trials in transplant oncology

Over the past two decades since the introduction of the Milan criteria, the field of transplant oncology has undergone a rapid development with a rising proportion of liver transplantations being performed for oncological indications. For many patients with liver tumours, transplantation represents the only chance for cure. However, many challenges remain, such as the adequate patient selection, management of post-transplant recurrence and refinement of neoadjuvant treatment protocols. This review provides an overview of the current state of the art of liver transplantation for oncological indications such as hepatocellular carcinoma, cholangiocarcinoma, colorectal liver metastasis and metastatic neuroendocrine tumours. We also summarize the ongoing research and explore future trends. Clinical trials are currently studying new diagnostic modalities, innovative pharmacological treatments, novel surgical techniques, downstaging regimens and new indications for liver transplantation. These emerging results will continue to shape the field of transplant oncology and provide us with the necessary tools to better select, treat and follow patients with liver tumours qualifying for liver transplantation.

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.

Surgical management of pancreatic neuroendocrine liver metastases

Pancreatic neuroendocrine tumors (PNET) are a heterogeneous group of neoplasms that vary in their clinical presentation, behavior and prognosis. The most common site of metastasis is the liver. Surgical resection of neuroendocrine liver metastases (NELM) is thought to afford the best long-term outcomes when feasible. Initial preoperative workup should include surveillance for carcinoid syndrome, screening for evidence of liver insufficiency, and performance of imaging specific to neuroendocrine tumors such as a somatostatin receptor positron emission tomography scan. Standard surgical principles apply to hepatic surgery for NELM, namely prioritizing low central venous pressure anesthesia, minimizing blood loss, knowledge of liver anatomy, generous use of intraoperative ultrasound, as well as safe parenchymal transection techniques and practices to avoid bile leakage. Knowledge of established prognostic factors may assist with patient selection, which is important for optimizing short- and long-term outcomes of hepatic resection. Adjunct therapies such as concomitant liver ablation are used frequently and are generally safe when used appropriately. For patients with synchronous resectable NELM, resection of the primary either in a staged or combined fashion is recommended. Primary tumor resection in the setting of unresectable metastatic disease is more controversial, however generally recommended if morbidity is acceptable. For patients who are not surgical candidates, due to either patient performance status or burden of liver disease, several liver-directed therapies such as transarterial embolization, chemoembolization, and radioembolization are available to assist with locoregional control, extend progression-free survival (PFS), and improve symptoms of carcinoid syndrome. Multiple systemic therapy options exist for patients with metastatic PNET which are often prioritized for those patients with advanced or progressive disease. A systematic approach in a multi-disciplinary setting is likely to result in the best long-term outcomes for patients with pancreatic NELM. Ongoing research is needed to determine the optimal patient selection for hepatic surgery as well as the ideal treatment sequencing for those patients with NELM.

Transarterial (chemo)embolisation versus no intervention or placebo for liver metastases

BACKGROUND

The liver is affected by two of the most common groups of malignant tumours: primary liver tumours and liver metastases from colorectal carcinoma or other extrahepatic primary cancers. Liver metastases are significantly more common than primary liver cancer, and long-term survival rate after radical surgical treatment is approximately 50%. However, R0 resection (resection for cure) is not feasible in the majority of people; therefore, other treatments have to be considered. One possible option is based on the concept that the blood supply to hepatic tumours originates predominantly from the hepatic artery. Transarterial chemoembolisation (TACE) of the hepatic artery can be achieved by administering a chemotherapeutic drug followed by vascular occlusive agents, and can lead to selective necrosis of the liver tumour while it may leave normal parenchyma virtually unaffected. This can also be performed without chemotherapy, which is called bland transarterial embolisation (TAE).

OBJECTIVES

To assess the beneficial and harmful effects of TAE or TACE compared with no intervention or placebo in people with liver metastases.

SEARCH METHODS

We searched the Cochrane Hepato-Biliary Group Controlled Trials Register, CENTRAL, MEDLINE, Embase, and four more databases (December 2019). We also searched two trials registers and the US Food and Drug Administration database (September 2019).

SELECTION CRITERIA

Randomised clinical trials assessing beneficial and harmful effects of TAE or TACE compared with no intervention or placebo for liver metastases.

DATA COLLECTION AND ANALYSIS

We followed standard Cochrane methodological procedures. We extracted information on participant characteristics, interventions, study outcomes, study design, and trial methods. Two review authors independently extracted data and assessed risk of bias. We assessed the certainty of evidence with GRADE. We resolved disagreements by discussion.

MAIN RESULTS

We included one randomised clinical trial with 61 participants (43 male and 18 female) with colorectal cancer with liver metastases: 22 received transarterial embolisation (TAE; hepatic artery embolisation), 19 received transarterial chemoembolisation (TACE; 5-fluorouracil hepatic artery infusion chemotherapy with degradable microspheres), and 20 received 'no active therapeutic intervention' as a control. Most tumours were synchronous, unresectable metastases involving up to 75% of the liver. Participants were followed for a minimum of seven months. The trial was at high risk of bias. Very-low-certainty evidence found inconclusive results for mortality at 44 months between the TAE and TACE versus no intervention groups (risk ratio (RR) 0.88, 95% confidence interval (CI) 0.74 to 1.06; 61 participants). Local recurrence was reported in 10 participants without any details about the group allocation. Very-low-certainty evidence found little or no difference in mortality between the TAE and no intervention groups (RR 0.91, 95% CI 0.75 to 1.10; 42 participants). Median survival was 7 months from trial entry (range 2 to 44 months) in the TAE group and 7.9 months (range 1 to 26 months) in the control group, and 8.7 months after diagnosis (range 2 to 49 months) in the TAE group and 9.6 months (range 1 to 27 months) in the control group. The trial authors reported the differences were not statistically significant. There were no reported side effects in the control group. In the TAE group, 18 participants experienced short-term symptoms of 'post-embolisation syndrome', which were relieved with symptomatic treatment; one participant also had a local puncture site haematoma. Very-low-certainty evidence found little or no difference in mortality between the TACE and no intervention groups (RR 0.83, 95% CI 0.65 to 1.07; 39 participants). Median survival in the TACE group was 10.7 months (range 3 to 38 months) from trial entry, and 13.0 months (range 3 to 38 months) after diagnosis. The trial authors reported that differences between groups were not statistically significant. All participants experienced short-term nausea, with or without vomiting, immediately after treatment; one participant developed a wound infection, and one developed deep vein thrombosis. The trial did not measure failure to clear liver metastases, time to progression of liver metastases, tumour response measures, or health-related quality of life. Cancer Research Campaign, a non-profit organisation, provided a grant for the trial; Pharmacia Ltd. delivered the Port-a-Cath arterial delivery systems and degradable starch microspheres. We identified one ongoing trial comparing TACE plus chemotherapy versus chemotherapy alone in people with unresectable colorectal liver metastases who failed with first-line chemotherapy (NCT03783559).

AUTHORS' CONCLUSIONS

Based on one, small randomised trial at high risk of bias, the evidence is very uncertain about the effect of TAE or TACE versus no active therapeutic intervention on mortality for people with liver metastases as the true effect may be substantially different. The trial did not measure failure to clear liver metastases, time to progression of liver metastases, tumour response measures, or health-related quality of life. Short-term, minor adverse events were recorded in the intervention groups only. Large trials, following current standards of conduct and reporting, are required to explore the benefits and harms of TAE or TACE compared with no intervention or placebo in people with resectable and unresectable liver metastasis.

Percutaneous ethanol injection for liver metastases

BACKGROUND

The liver is affected by two of the most common groups of malignant tumours: primary liver tumours and liver metastases from colorectal carcinoma or other extrahepatic primary cancers. Liver metastases are significantly more common than primary liver cancer, and the reported long-term survival rate after radical surgical treatment is approximately 50%. However, R0 resection (resection for cure) is not feasible in the majority of patients; therefore, other treatments have to be considered. One of these is percutaneous ethanol injection (PEI), which causes dehydration and necrosis of tumour cells, accompanied by small-vessel thrombosis, leading to tumour ischaemia and destruction of the tumour.

OBJECTIVES

To assess the beneficial and harmful effects of percutaneous ethanol injection (PEI) compared with no intervention, other ablation methods, or systemic treatments in people with liver metastases.

SEARCH METHODS

We searched the following databases up to 10 September 2019: the Cochrane Hepato-Biliary Group Controlled Trials Register; the Cochrane Central Register of Controlled Trials (CENTRAL), in the Cochrane Library; MEDLINE Ovid; Embase Ovid; Science Citation Index Expanded; Conference Proceedings Citation Index - Science; Latin American Caribbean Health Sciences Literature (LILACS); and the Cumulative Index to Nursing and Allied Health Literature (CINAHL). We also searched clinical trials registers such as ClinicalTrials.gov, the International Clinical Trials Registry Platform (ICTRP), and the US Food and Drug Administration (FDA) (17 September 2019).

SELECTION CRITERIA

Randomised clinical trials assessing beneficial and harmful effects of percutaneous ethanol injection and its comparators (no intervention, other ablation methods, systemic treatments) for liver metastases.

DATA COLLECTION AND ANALYSIS

We followed standard methodological procedures as outlined by Cochrane. We extracted information on participant characteristics, interventions, study outcomes, study design, and trial methods. Two review authors performed data extraction and assessed risk of bias independently. We assessed the certainty of evidence by using GRADE. We resolved disagreements by discussion.

MAIN RESULTS

We identified only one randomised clinical trial comparing percutaneous intratumour ethanol injection (PEI) in addition to transcatheter arterial chemoembolisation (TACE) versus TACE alone. The trial was conducted in China and included 48 trial participants with liver metastases: 25 received PEI plus TACE, and 23 received TACE alone. The trial included 37 male and 11 female participants. Mean participant age was 49.3 years. Sites of primary tumours included colon (27 cases), stomach (12 cases), pancreas (3 cases), lung (3 cases), breast (2 cases), and ovary (1 case). Seven participants had a single tumour, 15 had two tumours, and 26 had three or more tumours in the liver. The bulk diameter of the tumour on average was 3.9 cm, ranging from 1.2 cm to 7.6 cm. Participants were followed for 10 months to 43 months. The trial reported survival data after one, two, and three years. In the PEI + TACE group, 92%, 80%, and 64% of participants survived after one year, two years, and three years; in the TACE alone group, these percentages were 78.3%, 65.2%, and 47.8%, respectively. Upon conversion of these data to mortality rates, the calculated risk ratio (RR) for mortality at last follow-up when PEI plus TACE was compared with TACE alone was 0.69 (95% confidence interval (CI) 0.36 to 1.33; very low-certainty evidence) after three years of follow-up. Local recurrence was 16% in the PEI plus TACE group and 39.1% in the TACE group, resulting in an RR of 0.41 (95% CI 0.15 to 1.15; very low-certainty evidence). Forty-five out of a total of 68 tumours (66.2%) shrunk by at least 25% in the PEI plus TACE group versus 31 out of a total of 64 tumours (48.4%) in the TACE group. Trial authors reported some adverse events but provided very few details. We did not find data on time to mortality, failure to clear liver metastases, recurrence of liver metastases, health-related quality of life, or time to progression of liver metastases. The single included trial did not provide information on funding nor on conflict of interest.

AUTHORS' CONCLUSIONS

Evidence for the effectiveness of PEI plus TACE versus TACE in people with liver metastases is of very low certainty and is based on one small randomised clinical trial at high risk of bias. Currently, it cannot be determined whether adding PEI to TACE makes a difference in comparison to using TACE alone. Evidence for benefits or harms of PEI compared with no intervention, other ablation methods, or systemic treatments is lacking.

Non-Pharmacological Therapeutic Options for Liver Metastases in Advanced Neuroendocrine Tumors

The incidence of liver metastasis in digestive neuroendocrine tumors is high. Their presence appears as an important prognostic factor in terms of quality of life and survival. These tumors may be symptomatic because of the tumor burden itself and/or the hormonal hyper-secretion induced by the tumor. Surgery is the treatment of choice for resectable tumors and metastasis. Nevertheless, surgery is only possible in a small number of cases. The management of non-resectable liver metastasis is a challenge. The literature is rich but consists predominantly in small retrospective series with a low level of proof. Thus, the choice of one technique over another could be difficult. Local ablative techniques (radiofrequency) or trans-catheter intra-arterial liver-directed treatments (hepatic artery embolization, chemo-embolization, and radio-embolization) are frequently considered for liver metastasis. In the present review, we focus on these different therapeutic approaches in advanced neuroendocrine tumors, results (clinical and radiological), and overall efficacy, and summarize recommendations to help physicians in their clinical practice.