The emerging role of targeted therapies for advanced well-differentiated gastroenteropancreatic neuroendocrine tumors

A Comparison of the Outcomes of Transarterial Chemoembolization and Transarterial Radioembolization in the Management of Neuroendocrine Liver Metastases in Adults: A Systematic Review

The purpose of this article is to review the existing English scientific literature and determine the superior modality between transarterial chemoembolization (TACE) and radioembolization (TARE) in the treatment of neuroendocrine liver metastases (NELMs). To that end, we followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines to search PubMed, the Cochrane Library, and Google Scholar. We identified 14 observational studies and no randomized controlled trials (RCTs) investigating the use of TACE or TARE to treat NELM. We used the Newcastle-Ottawa Scale to assess the risk of bias in these studies. We concluded that TACE and TARE appeared to have similar outcomes when comparing overall survival, progression-free survival, radiological response, symptomatic response, and the incidence of severe adverse events. Further large-scale RCTs are needed to identify the superior modality conclusively. We also identified several unique prognostic factors for overall survival, such as the neutrophil-lymphocyte ratio, volumetric multiparametric magnetic resonance imaging, serum albumin, alkaline phosphatase, and pancreastatin.

Predictive Factors for Resistant Disease with Medical/Radiologic/Liver-Directed Anti-Tumor Treatments in Patients with Advanced Pancreatic Neuroendocrine Neoplasms: Recent Advances and Controversies

Simple Summary

Tumor resistance, both primary and acquired, is leading to increased complexity in the nonsurgical treatment of patients with advanced panNENs, which would be greatly helped by reliable prognostic/predictive factors. The importance in identifying resistance is being contributed to by the increased array of possible treatments available for treating resistant advanced disease; the variable clinical course as well as response to any given treatment approach of patients within one staging or grading system, the advances in imaging which are providing increasing promising results/parameters that correlate with grading/outcome/resistance, the increased understanding of the molecular pathogenesis providing promising prognostic markers, all of which can contribute to selecting the best treatment to overcome resistance disease. Several factors have been identified that have prognostic/predictive value for identifying development resistant disease and affecting overall survival (OS)/PFS with various nonsurgical treatments of patients with advanced panNENs. Prognostic factors identified for patients with advanced panNENs for both OS/PFSs include various clinically-related factors (clinical, laboratory/biological markers, imaging, treatment-related factors), pathological factors (histological, classification, grading) and molecular factors. Particularly important prognostic factors for the different treatment modalities studies are the recent grading systems. Most prognostic factors for each treatment modality for OS/PFS are not specific for a given treatment option. These advances have generated several controversies and new unanswered questions, particularly those related to their possible role in predicting the possible sequence of different anti-tumor treatments in patients with different presentations. Each of these areas is reviewed in this paper.

Abstract

Purpose: Recent advances in the diagnosis, management and nonsurgical treatment of patients with advanced pancreatic neuroendocrine neoplasms (panNENs) have led to an emerging need for sensitive and useful prognostic factors for predicting responses/survival. Areas covered: The predictive value of a number of reported prognostic factors including clinically-related factors (clinical/laboratory/imaging/treatment-related factors), pathological factors (histological/classification/grading), and molecular factors, on therapeutic outcomes of anti-tumor medical therapies with molecular targeting agents (everolimus/sunitinib/somatostatin analogues), chemotherapy, radiological therapy with peptide receptor radionuclide therapy, or liver-directed therapies (embolization/chemoembolization/radio-embolization (SIRTs)) are reviewed. Recent findings in each of these areas, as well as remaining controversies and uncertainties, are discussed in detail, particularly from the viewpoint of treatment sequencing. Conclusions: The recent increase in the number of available therapeutic agents for the nonsurgical treatment of patients with advanced panNENs have raised the importance of prognostic factors predictive for therapeutic outcomes of each treatment option. The establishment of sensitive and useful prognostic markers will have a significant impact on optimal treatment selection, as well as in tailoring the therapeutic sequence, and for maximizing the survival benefit of each individual patient. In the paper, the progress in this area, as well as the controversies/uncertainties, are reviewed.

Liver metastases

Liver metastases are commonly detected in a range of malignancies including colorectal cancer (CRC), pancreatic cancer, melanoma, lung cancer and breast cancer, although CRC is the most common primary cancer that metastasizes to the liver. Interactions between tumour cells and the tumour microenvironment play an important part in the engraftment, survival and progression of the metastases. Various cells including liver sinusoidal endothelial cells, Kupffer cells, hepatic stellate cells, parenchymal hepatocytes, dendritic cells, resident natural killer cells as well as other immune cells such as monocytes, macrophages and neutrophils are implicated in promoting and sustaining metastases in the liver. Four key phases (microvascular, pre-angiogenic, angiogenic and growth phases) have been identified in the process of liver metastasis. Imaging modalities such as ultrasonography, CT, MRI and PET scans are typically used for the diagnosis of liver metastases. Surgical resection remains the main potentially curative treatment among patients with resectable liver metastases. The role of liver transplantation in the management of liver metastasis remains controversial. Systemic therapies, newer biologic agents (for example, bevacizumab and cetuximab) and immunotherapeutic agents have revolutionized the treatment options for liver metastases. Moving forward, incorporation of genetic tests can provide more accurate information to guide clinical decision-making and predict prognosis among patients with liver metastases.

The Landmark Series: Pancreatic Neuroendocrine Tumors

Pancreatic neuroendocrine tumors (PNETs) comprise a heterogeneous group of neoplasms arising from pancreatic islet cells that remain relatively rare but are increasing in incidence worldwide. While significant advances have been made in recent years with regard to systemic therapies for patients with advanced disease, surgical resection remains the standard of care for most patients with localized tumors. Although formal pancreatectomy with regional lymphadenectomy is the standard approach for most PNETs, pancreas-preserving approaches without formal lymphadenectomy are acceptable for smaller tumors at low risk for lymph node metastases. Furthermore, observation of small, asymptomatic, low-grade PNETs is a safe, initial strategy and is generally recommended for tumors < 1 cm in size. In this Landmark Series review, we highlight the critical studies that have defined the surgical management of PNETs.

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.

Contemporary indications for and outcomes of hepatic resection for neuroendocrine liver metastases

BACKGROUND

Although surgical resection is associated with the best long-term outcomes for neuroendocrine liver metastases (NELM), the current indications for and outcomes of surgery for NELM from a population perspective are not well understood.

AIM

To determine the current indications for and outcomes of liver resection (LR) for NELM using a population-based cohort.

METHODS

A retrospective review of the 2014-2017 American College of Surgeons National Surgical Quality Improvement Program and targeted hepatectomy databases was performed to identify patients who underwent LR for NELM. Perioperative characteristics and 30-d morbidity and mortality were analyzed.

RESULTS

Among 669 patients who underwent LR for NELM, the median age was 60 (interquartile range: 51-67) and 51% were male. While the number of metastases resected ranged from 1 to 9, the most common (45%) number of tumors resected was one. The majority (68%) of patients had a largest tumor size of < 5 cm. Most patients underwent partial hepatectomy (71%) while fewer underwent a right or left hepatectomy or trisectionectomy. The majority of operations were open (82%) versus laparoscopic (17%) or robotic (1%). In addition, 30% of patients underwent intraoperative ablation while 45% had another concomitant operation including cholecystectomy (28.8%), bowel resection (20.2%), or partial pancreatectomy (3.4%). Overall 30-d morbidity and mortality was 29% and 1.3%, respectively. On multivariate analysis, American Society of Anesthesiologists class ≥ 3 [odds ratios (OR), OR = 2.089, 95% confidence intervals (CI): 1.197-3.645], open approach (OR = 1.867, 95%CI: 1.148-3.036), right hepatectomy (OR = 1.618, 95%CI: 1.014-2.582), and prolonged operative time of > 230 min (OR = 1.731, 95%CI: 1.168-2.565) were associated with higher 30-d morbidity while intraoperative ablation and concomitant procedures were not.

CONCLUSION

LR for NELM was performed with relatively low postoperative morbidity and mortality. Concomitant procedures performed at the time of LR did not increase morbidity.

Tumor Contrast-Enhancement for Monitoring of PRRT 177Lu-DOTATATE in Pancreatic Neuroendocrine Tumor Patients

Background: Therapy monitoring of cancer treatment by contrast-enhanced CT (CECT), applying response evaluation criteria in solid tumors criteria version 1. 1 (RECIST 1.1) is less suitable for neuroendocrine tumors (NETs) which, when responding, tend to show stabilization rather than shrinkage. New methods are needed to further classify patients in order to identify non-responders at an early stage and avoid unnecessary adverse effects and costs. Changes in arterial tumor attenuation and contrast-enhancement could be used to identify the effect of therapy, perhaps even in early stages of treatment.

Methods: Patients with metastatic pancreatic NETs (PNETs) receiving peptide receptor radionuclide therapy (PRRT) with ¹⁷⁷Lu-DOTATATE underwent CECT at baseline, mid-treatment (PRRT cycles 3–5) and at follow-up, 3 months after the last PRRT cycle. At baseline CECT, the liver metastasis with the highest arterial attenuation was identified in each patient. The fold changes in arterial tumor attenuation (Hounsfield Units, HU), contrast-enhancement (HU), and transversal tumor area (cm²) between CECT at baseline, mid-treatment and follow-up were calculated. Correlation of the tumor metrics to outcome parameters such as progression-free survival (PFS) and time to best response was performed.

Results: Fifty-two patients were included (27 men, 25 women), median age 60 years (range 29–80), median Ki-67 8% (range 1–30). Six patients had grade 1 PNETs, forty had grade 2 and four had grade 3 tumors. As an internal control, it was first tested and established that the tumor contrast-enhancement was not merely related to that of the abdominal aorta. The mean ± SD arterial attenuation of the liver metastases was similar at baseline, 217 ± 62 HU and at mid-treatment, 238 ± 80 HU and then decreased to 198 ± 62 HU at follow-up, compared to baseline (p = 0.024, n = 52) and mid-treatment (p = 0.0004, n = 43). The transversal tumor area decreased 25% between baseline and follow-up (p = 0.013, n = 52). Tumor contrast-enhancement increased slightly from baseline to mid-treatment and these fold changes correlated with PFS (R² = 0.33, p = 0.0002, n = 37) and with time to best response (R² = 0.34, p < 0.0001, n = 37).

Conclusions: Early changes in contrast-enhancement and arterial attenuation in PNET liver metastases may for CECT monitoring of PRRT yield complementary information to evaluation by RECIST 1.1.

Transarterial Chemoembolization vs Radioembolization for Neuroendocrine Liver Metastases: A Multi-Institutional Analysis

BACKGROUND

Liver-directed hepatic arterial therapies are associated with improved survival and effective symptom control for patients with unresectable neuroendocrine liver metastases (NELM). Whether transarterial chemoembolization (TACE) or transarterial radioembolization (TARE) with yttrium-90 (y-90) are associated with improved short- or long-term outcomes is unknown.

STUDY DESIGN

A retrospective review was performed of all patients with NELM undergoing transarterial therapies, from 2000 to 2018, at 2 academic medical centers. Postoperative morbidity, radiographic response according to response evaluation criteria in solid tumors (RECIST) criteria, and long-term outcomes were compared between patients who underwent TACE vs TARE.

RESULTS

Among 248 patients with NELM, 197 (79%) received TACE and 51 (21%) received TARE. While patients who underwent TACE were more likely to have carcinoid syndrome, larger tumors, and higher chromogranin A levels, there was no difference in tumor differentiation, primary site, bilobar disease, or synchronous presentation. Nearly all TARE treatments (92%) were performed as outpatient procedures, while 99% of TACE patients spent at least 1 night in the hospital. There were no differences in overall morbidity (TARE 13.7% vs TACE 22.6%, p = 0.17), grade III/IV complication (5.9% vs 9.2%, p = 0.58), or 90-day mortality. The disease control rate (DCR) on first post-treatment imaging (RECIST partial/complete response or stable disease) was greater for TACE compared with TARE (96% vs 83%, p < 0.01). However, there was no difference in median overall survival (OS, 35.9 months vs 50.1 months, p = 0.3) or progression-free survival (PFS, 15.9 months vs 19.9 months, p = 0.37).

CONCLUSIONS

In this retrospective multi-institutional analysis, both TACE and TARE with Y-90 were safe and effective liver-directed therapies for unresectable NELM. Although TARE was associated with a shorter length of hospital stay, TACE demonstrated improved short-term DCR, and both resulted in comparable long term outcomes.