Capecitabine and temozolomide in grade 1/2 neuroendocrine tumors: a Spanish multicenter experience

A Comprehensive Review on Neuroendocrine Neoplasms: Presentation, Pathophysiology and Management

Neuroendocrine neoplasms (NENs) are a group of heterogeneous tumors with neuroendocrine differentiation that can arise from any organ. They account for 2% of all malignancies in the United States. A significant proportion of NEN patients experience endocrine imbalances consequent to increased amine or peptide hormone secretion, impacting their quality of life and prognosis. Over the last decade, pathologic categorization, diagnostic techniques and therapeutic choices for NENs-both well-differentiated neuroendocrine tumors (NETs) and poorly differentiated neuroendocrine carcinomas (NECs)-have appreciably evolved. Diagnosis of NEN mostly follows a suspicion from clinical features or incidental imaging findings. Hormonal or non-hormonal biomarkers (like serum serotonin, urine 5-HIAA, gastrin and VIP) and histology of a suspected NEN is, therefore, critical for both confirmation of the diagnosis and classification as an NET or NEC. Therapy for NENs has progressed recently based on a better molecular understanding, including the involvement of mTOR, VEGF and peptide receptor radionuclide therapy (PRRT), which add to the growing evidence supporting the possibility of treatment beyond complete resection. As the incidence of NENs is on the rise in the United States and several other countries, physicians are more likely to see these cases, and their better understanding may support earlier diagnosis and tailoring treatment to the patient. We have compiled clinically significant evidence for NENs, including relevant changes to clinical practice that have greatly updated our diagnostic and therapeutic approach for NEN patients.

Chemotherapy in Well Differentiated Neuroendocrine Tumors (NET) G1, G2, and G3: A Narrative Review

Neuroendocrine tumors (NETs) are rare neoplasms with a wide spectrum of clinical behavior, from the long survival of well-differentiated NETs to the dismal prognosis of high-grade neuroendocrine carcinomas (NECs), being G3 NETs a recently recognized intermediate entity. While the role of chemotherapy is well established in NECs, data on NETs mostly derives from small studies, experts' opinions, and extrapolating results from small-cell lung cancer studies. This narrative review aims to summarize available evidence about the use of chemotherapy in the setting of G1-2 NETs and G3 NETs. We performed literature research in PubMed Library for all articles published up to September 2022 about the efficacy of chemotherapy in NETs. Treatment regimens with STZ-5FU, CAPTEM, and anti-metabolite-based treatment are the most active and tolerated in gastroenteropancreatic NETs (GEP-NETs) G1-G2, while platinum-based regimens (FOLFOX/XELOX) and TEM/CAPTEM showed the best activity in thoracic NETs. Solid evidence about chemotherapy efficacy in G3 NETs is still lacking. Literature data support the use of chemotherapy in low-intermediate grade NETs after the failure of other therapies or if tumor shrinkage is needed. Studies assessing G3 NETs independently from NECs are needed to better understand the role of chemotherapy in this setting.

Capecitabine and Temozolomide (CAPTEM) in Advanced Neuroendocrine Neoplasms (NENs): A Systematic Review and Pooled Analysis

Background

Retrospective studies and single center experiences suggest a role of capecitabine combined with temozolomide (CAPTEM) in neuroendocrine tumors (NENs).

Methods

We performed a systematic review to assess the efficacy and safety of CAPTEM in patients affected with NENs, with the aim to better clarify the role of this regimen in the therapeutic algorithm of NENs.

Results

A total of 42 articles and 1818 patients were included in our review. The overall disease control rate was 77% (range 43.5%-100%). The median progression free survival ranged from 4 to 38.5 months, while the median overall survival ranged from 8 to 103 months. Safety analysis showed an occurrence of G3-G4 toxicities in 16.4% of the entire population. The most common toxicities were hematological (27.2%), gastrointestinal (8.3%,) and cutaneous (3.2%).

Conclusion

This systematic review demonstrated that CAPTEM was an effective and relatively safe treatment for patients with advanced well-moderate differentiated NENs of gastroenteropancreatic, lung and unknown origin.

Chemotherapy in Neuroendocrine Tumors

The role for cytotoxic chemotherapy in patients with well-differentiated neuroendocrine tumors (NETs) remains debated. Compared to patients with poorly differentiated neuroendocrine carcinomas (NECs) where chemotherapy is utilized ubiquitously, chemotherapy may play a more select role in patients with certain types of NETs (e.g., pancreatic tumors, higher grade tumors, and tumors possessing DNA damage repair defects). The primary types of chemotherapy that have been tested in patients with NETs include alkylating agent- and platinum agent-based combinations. Across regimens, chemotherapy appears to elicit greater antitumor activity in patients with pancreatic or grade 3 NETs. The role for chemotherapy in lower grade extra-pancreatic NETs remains undefined. Furthermore, while chemotherapy has demonstrated clinically meaningful benefit for patients in the systemic setting, its role in the adjuvant or neoadjuvant setting is as-of-yet undetermined. Finally, efforts to combine chemotherapy with targeted therapy and peptide receptor radionuclide therapy are ongoing, in hopes of improving the cytoreductive treatment options for patients with NETs.

Chemotherapy in NEN: still has a role?

Neuroendocrine neoplasms (NENs) comprise a broad spectrum of tumors with widely variable biological and clinical behavior. Primary tumor site, extent of disease, tumor differentiation and expression of so matostatin receptors, proliferation and growth rates are the major prognostic factors that determine the therapeutic strategy. Treatment options for advanced disease have considerably expanded in recent years, particularly for well differentiated tumors (NETs). Novel drugs approved over the past decade in this context include somatostatin analogues and ¹⁷⁷Lu-oxodotreotide for somatostatin-receptor-positive gastroenteropancreatic (GEP) NETs, sunitinib for pancreatic NETs (P-NETs), and everolimus for P-NETs and non-functioning lung or gastrointestinal NETs. Nevertheless, chemotherapy remains an essential component of the treatment armamentarium of patients with NENs, particularly of patients with P-NETs or those with bulky, symptomatic or rapidly progressive tumors (generally G3 or high-G2 NENs). In this manuscript we will comprehensively review available evidence related to the use of chemotherapy in lung and GEP NENs and will critically discuss its role in the treatment algorithm of this family of neoplasms.

Temozolomide alone or in combination with capecitabine in patients with advanced neuroendocrine neoplasms: an Italian multicenter real-world analysis

PURPOSE

Temozolomide (TEM) has been reported to be active alone or in combination with capecitabine (CAP) in patients with neuroendocrine neoplasms (NENs). We retrospectively evaluated activity and toxicity of TEM-based chemotherapy in patients with advanced NENs and explored the potential correlation with clinical/biological factors.

METHODS

Patients received oral TEM alone or in combination with CAP. Objective response rate (ORR) [complete response + partial response (PR)], median progression-free survival (mPFS), and toxicity were calculated. The O⁶-methylguanine-DNA-methyltransferase (MGMT) gene inactivation status in tumor tissue was evaluated by pyrosequencing.

RESULTS

From September 2008 to April 2020, 170 patients (84% progressive on different therapies) were consecutively treated, 114 (67%) patients received TEM-CAP and 56 (33%) TEM alone. Primary tumor sites were: pancreas 98 (58%), gastrointestinal tract 21 (12%), lung 35 (21%), and unknown 16 (9%). The ORR was 28% for the whole population (33% for TEM-CAP and 18% for TEM as single agent). The median OS (mOS) and mPFS of the whole population were 35.6 months (32.6-48.7) and 14.7 months (10.1-18.3), respectively. There were 48% PR in the MGMT hypermethylated, mainly in pancreatic NENs. Vomiting and leukopenia were the most frequent grade 3/4 toxicity.

CONCLUSIONS

This large retrospective analysis suggested that a TEM-based chemotherapy is active in advanced, pretreated NEN patients. It generated solid hypotheses that warrant a future prospective study in a biological homogeneous NEN population and clinical setting.

A Ki-67 Index to Predict Treatment Response to the Capecitabine/Temozolomide Regimen in Neuroendocrine Neoplasms: A Retrospective Multicenter Study

OBJECTIVE

The efficacy of the capecitabine/temozolomide (CAPTEM) regimen has been demonstrated in metastatic neuroendocrine neoplasms (NENs), but because of varying response rates among the patients, biomarkers to predict its response are greatly needed. Here, we investigated the clinical utility of a Ki-67 index to predict the CAPTEM regimen objective responses and select patients who could benefit from this regimen.

METHODS

Metastatic NENs patients treated with the CAPTEM regimen from 4 high-volume medical centers were selected and grouped in a training and validation cohort. The classification and regression tree (CART) was generated to identify the optimal threshold of Ki-67 for stratifying the patients into different Ki-67 range groups based on their response to the CAPTEM regimen.

RESULTS AND CONCLUSIONS

The overall response rate (ORR) and disease control rate of the entire cohort (N = 151) were 26.5 and 76.2%, respectively, with a median progression-free survival (PFS) of 12.0 months. CART analysis showed that patients in the Ki-67 range group 10-40% demonstrated a significantly higher ORR than those in Ki-67 >40 and <10% groups (p < 0.001 in the training cohort and p = 0.036 in the validation cohort). Response to the CAPTEM regimen was not influenced by the expression of O6-methylguanine-DNA methyltransferase or primary tumor location. Multivariate analysis identified the Ki-67 index as the only independent prognostic factor for overall survival (p = 0.031) and PFS (p = 0.006). The proposed Ki-67 index was externally validated and could be used to clinically identify suitable metastatic NENs patients who could achieve an optimal cytoreduction using the CAPTEM regimen.

Advances in the Diagnosis and Management of Well-Differentiated Neuroendocrine Neoplasms

Neuroendocrine neoplasms constitute a diverse group of tumors that derive from the sensory and secretory neuroendocrine cells and predominantly arise within the pulmonary and gastrointestinal tracts. The majority of these neoplasms have a well-differentiated grade and are termed neuroendocrine tumors (NETs). This subgroup is characterized by limited proliferation and patients affected by these tumors carry a good to moderate prognosis. A substantial subset of patients presenting with a NET suffer from the consequences of endocrine syndromes as a result of the excessive secretion of amines or peptide hormones, which can impair their quality of life and prognosis. Over the past 15 years, critical developments in tumor grading, diagnostic biomarkers, radionuclide imaging, randomized controlled drug trials, evidence-based guidelines, and superior prognostic outcomes have substantially altered the field of NET care. Here, we review the relevant advances to clinical practice that have significantly upgraded our approach to NET patients, both in diagnostic and in therapeutic options.

Influence of Gender on Therapy and Outcome of Neuroendocrine Tumors of Gastroenteropancreatic Origin: A Single-Center Analysis

Introduction

Gender-specific treatment is gaining growing attention in various fields of medicine. In gastrointestinal cancer, influence of sex on outcome has been discussed, while this has not been the case in neuroendocrine tumors. Overall, the incidence of neuroendocrine neoplasms is rising, especially for appendiceal neuroendocrine neoplasms in women. Also, women seem to have a slight advantage in response to therapy, especially for liver metastases.

Objectives

This single-center analysis aimed to investigate gender-specific differences in our cohort related to distribution, therapy, and outcome.

Methods

Patients from the NET registry as well as the clinic database were evaluated retrospectively concerning overall survival and response to therapy with respect to gender. A subgroup analysis was carried out for patients with low grading and response to chemotherapy, as well as for patients with good and moderate grading receiving peptide receptor radionuclide therapy and for a group of patients with liver surgery.

Results

No specific differences could be detected for overall survival or response to therapy between male and female patients. Mean survival was estimated with 242.2 months (±10.39 SD) altogether and 221.7 months (± 13.02 SD) for male patients and 253.5 months (±15.24 SD) for female patients from the NET registry from initial diagnosis. There was no significant difference between female and male patients (p = 0.136). For patients receiving chemotherapy, overall survival from initial diagnosis was calculated with 26 months (±2.59) and did not show any significant differences between female and male patients 24.8 months (±2.81 SD) vs. 27.8 months (±3.86 SD, p = 0.87). Patients undergoing peptide receptor radionuclide therapy showed a median progression-free survival of 26.9 months (±2.82 SD), with 16.9 (±5.595 SD) and 26.9 months (±3.019 SD) for male and female patients, respectively (p = 0.2). In the group of patients with liver surgery, female patients reached an estimated overall survival of 64.7 months (±4.16 SD), male patients 65.1 months (±2.79 SD, p = 0.562).

Conclusion

Our cohort did not reveal significant differences in outcome and response to therapy with regards to gender.

Capecitabine and Temozolomide in Patients with Advanced Pulmonary Carcinoid Tumours

BACKGROUND

Temozolomide and capecitabine (CAPTEM) chemotherapy is known to be active in patients with pancreatic neuroendocrine tumours.

OBJECTIVE

This retrospective analysis set out to describe the efficacy and toxicity of CAPTEM in patients with advanced pulmonary carcinoids (PCs).

METHODS

Patients were included with advanced PC who had been treated with a maximum of 6 cycles of oral temozolomide 200 mg/m2 on days 10-14 and capecitabine 750 mg/m2 b.i.d. on days 1-14, repeated every 28 days, -followed by monthly intramuscular injection of octreotide 30 mg long-acting release as maintenance treatment.

RESULTS

Of the 33 patients, all with well-differentiated PC, 61% had atypical carcinoid, 36% had Ki-67 index >10% and 42% had ≥3 organs involved by metastasis. CAPTEM was administered as first-line treatment in 42% of patients, and 17% had received prior somatostatin analogue treatment. Six patients (18%) achieved a partial response, 19 (58%) had stable disease and 8 (24%) developed progressive disease. After a median time of follow-up of 34.8 months, median progression-free survival (PFS) was 9.0 months and median overall survival 30.4 months. Median duration of disease response was 21.7 months and median duration of disease control 9.7 months. Patients with multi-organ metastasis had shorter PFS, but only when treated as second or third line with CAPTEM (p = 0.023).

CONCLUSIONS

CAPTEM induced a modest response and PFS rate, comparable to other studies with temozolomide in patients with advanced PC. The efficacy of CAPTEM should be compared to that of monotherapy with temozolomide in a prospective clinical trial.

Clinical analysis of 547 patients with neuroendocrine tumors in a Chinese population: A single-center study

BACKGROUND

Neuroendocrine tumors (NETs) are rare, which has resulted in a lack of published data on their epidemiology and clinical features. We therefore aimed to investigate the epidemiology, clinical features, treatments, and prognosis of patients with NETs.

METHODS

The clinicopathologic characteristics of 547 patients who were pathologically diagnosed with NETs were retrospectively analyzed, including age, sex, primary and metastatic sites, symptoms, pathology, treatment, and prognosis.

RESULTS

The 547 patients had a wide age range (9-87 years), with a male to female ratio of 1:1.1. The primary tumor sites included 413 in the digestive system, 74 in the lung, 15 in the mediastinum, 8 in unknown sites, and 37 in other sites. Of the 413 patients with digestive system NETs, the pancreas, rectum, and stomach were the most common primary sites. Blood metastases were found in 84 patients at initial diagnosis, and the liver, bone, and lung were the most frequent sites of metastasis. Lymph node metastases were found in 82 patients at initial diagnosis. Surgery and chemotherapy were the most widely applied treatments. Statistical analysis showed that age <50 years, female sex, lower-grade tumor, no distant metastasis, intestinal NET and surgery indicated a favorable prognosis.

CONCLUSIONS

A difference between China and other countries is that small intestinal NETs are quite common in other countries but are rare in China. In China, the most common primary sites are the pancreas, rectum, and stomach. Furthermore, no unified treatments exist, though prognoses could be improved by using methods such as surgery, targeted therapies, and somatostatin analogs.

CLINICAL TRIAL REGISTRATION

This study was not a clinical trial.

Temozolomide Alone or Combined with Capecitabine for the Treatment of Advanced Pancreatic Neuroendocrine Tumor

BACKGROUND

The combination of capecitabine (CAP) with temozolomide (TEM) chemotherapy in advanced pancreatic neuroendocrine tumors (PanNET) relies on limited evidence. We compared TEM-CAP to TEM alone in patients with advanced PanNET.

METHODS

Consecutive patients with advanced PanNET treated with TEM or TEM-CAP between 2004 and 2017 in three expert centers were included. Progression-free survival (PFS), tolerance, tumor response, and overall survival were compared between the two groups. Propensity-based analyses were performed to reduce confounding bias due to the nonrandomized setting.

RESULTS

TEM and TEM-CAP were administered to 38 patients and 100 patients, respectively, with a median age of 58 years. The patients in the TEM group more often had hormonal syndromes (p = 0.03), a longer median delay to diagnosis (p = 0.001), and a higher number of pretreatment lines (p < 0.001). The performance status was 0 in 58% versus 65% of the patients, and tumor's median Ki-67 index was 8% versus 11%, respectively. Tolerance was similar, except that there were more cases of asthenia in the TEM group (p = 0.017) and more cases of hand-foot syndrome in the TEM-CAP group (p = 0.025). The objective response rate was 34% versus 51% (p = 0.088). The raw median PFS was similar with TEM and with TEM-CAP (21.4 vs. 19.8 months, p = 0.84). Although CAP tended to decrease the risk of progression in Cox multivariate analysis (HR 0.65, p = 0.12), it had no effect after adjustment for the propensity score (HR 1.06, p = 0.80).

CONCLUSIONS

TEM-CAP might not prolong PFS but might achieve a higher response rate than TEM alone. Hence, TEM-CAP might be preferred when tumor shrinkage is the main therapeutic objective. Otherwise, TEM might be adequate for patients with an impaired performance status or in case of extrahepatic metastases.

Activity and Safety of Standard and Prolonged Capecitabine/Temozolomide Administration in Patients with Advanced Neuroendocrine Neoplasms

BACKGROUND

Capecitabine and temozolomide combination (CAPTEM) is associated with high response rates in patients with advanced neuroendocrine neoplasms (NENs). We evaluated the real-world activity and safety of CAPTEM from 3 NEN centers.

METHODS

Clinicopathological characteristics and outcomes of patients treated with CAPTEM for bulky or progressive disease (PD) were retrospectively analyzed. -Results: Seventy-nine patients with gastroenteropancreatic (grades 1-2 [n = 38], grade 3 [n = 24]) and lung/thymic (n = 17) NENs were included. Median treatment duration was 12.1 months (range 0.6-55.6). Overall, partial responses (PRs) occurred in 23 (29.1%), stable (SD) in 24 (30.4%), and PD in 28 (35.4%) patients. Median progression-free survival (PFS) and overall survival (OS) were 10.1 (6-14.2) and 102.9 months (43.3-162.5), respectively. On univariate analysis, NENs naive to chemotherapy and low Ki67 were associated with favorable responses (partial response [PR] + SD; p = 0.011 and 0.045), PFS (p < 0.0001 and 0.002) and OS (p = 0.005 and 0.001). Primary site (pancreas and lung/thymus) was also a significant prognostic factor for PFS (p < 0.0001) and OS (p < 0.0001). On multivariate analysis, gastrointestinal and unknown primary NENs (hazard ratio [HR] 0.3, 95% CI 0.1-0.8, p = 0.009 and p = 0.018) and prior surgery (HR 2.4, 95% CI 11-4.9, p = 0.021) were independent prognostic factors for PFS. Ki-67 was a poor predictor for favorable response in receiver operating characteristic analysis (area under the curve 0.678). Safety analysis of CAPTEM indicated rare events of serious (grades 3-4) toxicities (n = 4) and low discontinuation rates (n = 8) even in patients with prolonged administration (>12 months).

CONCLUSIONS

CAPTEM treatment can be an effective and safe treatment even after prolonged administration for patients with NENs of various sites and Ki67 labeling index, associated with significant favorable responses and PFS.

Comparison of Temozolomide-Capecitabine to 5-Fluorouracile-Dacarbazine in 247 Patients with Advanced Digestive Neuroendocrine Tumors Using Propensity Score Analyses

INTRODUCTION

Although chemotherapy combining 5-fluorouracil (5FU)-dacarbazine (DTIC) or temozolomide (TEM)-capecitabine (CAP) is extensively used in patients with neuroendocrine tumors (NET), they were never compared. We compared their tolerance and efficacy in advanced NET.

METHODS

We evaluated the records of consecutive patients with pancreatic or small-intestine advanced NET who received 5FU-DTIC or TEM-CAP between July 2004 and December 2017 in 5 French centers. Tolerance, tumor response and progression-free survival (PFS) were compared. Factors associated with PFS were analyzed using Cox multivariate regression model. To reduce the confounding bias of the nonrandomized design, PFS was compared using propensity score analyses.

RESULTS

Ninety-four (5FU-DTIC) patients and 153 (TEM-CAP) patients were included. Pancreatic NET represented 82.3% of cases and 17.1, 61.8 and 10.9% of patients had G1, G2 or G3 NET respectively. Progression at baseline was reported in 92.7% of patients with available data. Grades 3-4 adverse events occurred in 24.7 and 8.5% of TEM-CAP and 5FU-DTIC patients respectively (p = 0.002). The overall response rate was 38.3 and 39.2% respectively (p = 0.596). Median PFS on raw analysis was similar to 5FU-DTIC and TEM-CAP (13.9 vs. 18.3 months, respectively p = 0.86). TEM-CAP was associated with an increased risk of progression on the raw multivariate analysis (hazard ratio [HR] 1.90, 95% CI [1.32-2.73], p = 0.001) and when adjusted on propensity score (HR 1.65, 95% CI [1.18-2.31], p = 0.004).

CONCLUSION

PFS may be longer with 5FU-DTIC than TEM-CAP in patients with advanced NET. Although patients often prefer oral chemotherapy, 5FU-DTIC is a relevant alternative. A randomized comparison is needed to confirm these results.

Current best practice in the management of neuroendocrine tumors

Neuroendocrine neoplasms are rare tumors that display marked heterogeneity with varying natural history, biological behavior, response to therapy and prognosis. Their management is complex, particularly as a number of them may be associated with a secretory syndrome and involve a variety of options. A number of factors such as proliferation rate, degree of differentiation, functionality and extent of the disease are mostly utilized to tailor treatment accordingly, ideally in the context of a multidisciplinary team. In addition, a number of relevant scientific societies have published therapeutic guidelines in an attempt to direct and promote evidence-based treatment. Surgery remains the treatment of choice with an intention to cure while it may also be recommended in some cases of metastatic disease and difficult to control secretory syndromes. Long-acting somatostatin analogs constitute the main treatment for the majority of functioning tumors, whereas specific evolving agents such as telotristat may be used for the control of carcinoid syndrome and related sequelae. In patients with advanced disease not amenable to surgical resection, treatment options include locoregional therapies, long-acting somatostatin analogs, molecular targeted agents, radionuclides, chemotherapy and recently immunotherapy, alone or in combination. However, the ideal time of treatment initiation, sequence of administration of different therapies and identification of robust prognostic markers to select the most appropriate treatment for each individual patient still need to be defined.

Safety and efficacy of combining capecitabine and temozolomide (CAPTEM) to treat advanced neuroendocrine neoplasms: A meta-analysis

Retrospective studies have suggested that capecitabine combined with temozolomide (CAPTEM) is effective for treating patients with advanced neuroendocrine neoplasms (NENs); however, the efficacy and safety of this regimen needs to be verified by high-quality evidence or results of randomized controlled trials.We carried out a meta-analysis to evaluate the safety and effectiveness of a CAPTEM protocol for patients with advanced NENs. Systematic electronic literature searches were conducted using PubMed, EMBASE, and the Cochrane Library, and among meeting abstracts of the American Society of Clinical Oncology, European Society for Medical Oncology, European Neuroendocrine Tumor Society, and North American Neuroendocrine Tumor Society, up to June 30, 2017. We selected studies describing CAPTEM regimens for treating advanced NENs and reported on tumor response and/or toxicities according to clear World Health Organization (WHO) grading of patients. Three reviewers independently and repeatedly identified studies, extracted data, and assessed the quality of the literature. A single-proportion meta-analysis was applied to included articles.Fifteen studies with a total of 384 individuals were included. Medium overall survival in most studies was more than 12 months, whereas medium progression-free survival was similar or slightly higher than that in studies using other treatment regimes. Disease control rate of CAPTEM administration for patients with NENs was 72.89% (95% confidence interval, 64.04-81.73%; I = 82.4%; P < .01). WHO grade 3 to 4 toxicities, such as thrombocytopenia (3.36%), neutropenia (0.69%), lymphopenia (0.65%), anemia (0.59%), mucositis (0.57%), fatigue (0.54%), diarrhea (0.49%), nausea (0.39%), and transaminase elevation (0.13%) were reported in the trials included.CAPTEM is effective and relatively safe for treating patients with advanced NENs.

Current Chemotherapy Use in Neuroendocrine Tumors

The role of chemotherapy in neuroendocrine tumors (NETs) has evolved with the development of other effective systemic therapies. At the same time, the evolving classification of NETs by grade has allowed for prognostic stratification. Chemotherapy is not routinely used for grade 1 to 2 NETs, but capecitabine (CAPTEM) or streptozocin-based regimens may be used, particularly for pancreatic NETs. In contrast, poorly differentiated grade 3 NETs are usually treated with platinum doublet chemotherapy. There is no consensus for the treatment of well-differentiated G3 NETs, but platinum doublets or CAPTEM are reasonable options.

The Treatment Landscape and New Opportunities of Molecular Targeted Therapies in Gastroenteropancreatic Neuroendocrine Tumors

Neuroendocrine neoplasms (NENs) are a heterogeneous group of neoplasms that originate from neuroendocrine stem cells and express both neural and endocrine markers. They are found in almost every organ, and while NENs are mostly associated with slow growth, complications due to the uncontrolled secretion of active peptides, and metastatic disease, may significantly impair the quality of life and can ultimately lead to the death of affected individuals. Expanding knowledge of the genetic, epigenetic, and proteomic landscapes of NENs has led to a better understanding of their molecular pathology and consequently increased treatment options for patients. Here, we review the principal breakthroughs in NEN treatment management, owing largely to omics technologies over the last few years, current recommendations of systemic treatment, and ongoing research into the identification of predictive and response biomarkers based on molecular targeted therapies.

The Role of Cytotoxic Chemotherapy in Advanced Pancreatic Neuroendocrine Tumors

BACKGROUND

Pancreatic neuroendocrine tumors (PNETs) are rare neoplasms accounting for less than 5% of all pancreatic malignancies. These tumors are characterized by clinical and prognostical heterogeneity and are predominantly diagnosed in a metastatic stage. Cytotoxic chemotherapy, along with alkylating agents and antimetabolites as well as molecular targeted agents (everolimus, sunitinib), is used in the treatment of advanced PNETs. After the approval of lanreotide for unresectable PNETs, an additional therapeutic option has become available; however, the best sequence of therapies and patient stratification to different treatments remains challenging. Furthermore, no randomized phase-3 trials or head-to-head comparisons are available to support treatment decisions.

SUMMARY

The publication of 3 large single-center retrospective studies on streptozocin-(STZ)-based chemotherapy in advanced PNETs in 2015 confirmed the effectiveness of this treatment as described in previously reported trials. All studies investigated markers for progression-free and overall survival and strongly supported the value of the Ki-67 index as a robust prognostic marker. Interestingly, chemotherapy consistently displayed antitumor efficacy in different therapeutic lines. Moreover, a recent study of dacarbazine (DTIC) in a cohort of patients predominantly with PNETs demonstrated that a once monthly infusional DTIC schedule was well tolerated and yielded similar response rates (RR) as STZ-based schedules. Given the overall good tolerability of a monthly infusion and RR similar to STZ schedules, DTIC thus represents a feasible alternative or additional treatment option for PNETs. In this article, we review the current standard and summarize the most recent advances in the field of cytotoxic chemotherapy for PNET patients. Key Messages: (1) Despite the lack of phase3 trials, cytotoxic chemotherapy offers efficacy for patients with advanced PNETs; (2) the best therapeutic option and sequence remain open since comparable randomized studies are lacking; (3) careful patient selection and treatment stratification may increase overall outcome; and (4) currently, no biomarkers for clinical routine exist to predict response to chemotherapy.

Capecitabine and Temozolomide in Neuroendocrine Tumor of Unknown Primary

Incidence of low grade well-differentiated neuroendocrine tumors (NET) is on the rise. The North American Neuroendocrine Tumor Society estimates that the United States has more than 150,000 gastroenteropancreatic NET patients. About 10% of metastatic NETs can be unknown primary, and due to their rarity, dedicated treatment algorithms and regimens are not defined. Combination of capecitabine and temozolomide (CAPTEM) is one of the systemic treatments used in gastroenteropancreatic NETs. We explored clinical activity of CAPTEM in NET of unknown primary. Methods. Retrospective review of NET of unknown primary managed at the University of Kentucky over the past five years (2012–2016). Result. 56 patients with NET of unknown primary were identified; 12 patients were treated with CAPTEM. Median progression-free survival on CAPTEM in grade II and grade III NET of unknown primary was 10.8 and 7 months, respectively. Six patients showed reduction in metastatic tumor volume at three-month CT scan. Three patients had stable disease and three patients showed disease progression at the first surveillance scan. Common side-effects were as follows: four patients developed grade II thrombocytopenia, three patients developed grade I lymphocytopenia, and two patients developed hand foot syndrome (grades I and III). Six patients developed grade I fatigue. Conclusion. CAPTEM should be considered for grades I and II NET of unknown primary, especially in the case of visceral crisis or bulky disease.

Ex vivo activity of cytotoxic drugs and targeted agents in small intestinal neuroendocrine tumors

Small intestinal neuroendocrine tumors (SI-NETs) are generally considered resistant to systemic treatment. To date, predictive markers for drug activity are lacking. Tumor samples from 27 patients with SI-NETs were analyzed ex vivo for sensitivity to a panel of cytotoxic drugs and targeted agents using a short-term total cell kill assay. Samples of renal cancer, colorectal cancer (CRC), ovarian cancer and chronic lymphocytic leukemia (CLL) were included for comparison. For the SI-NET subset, drug sensitivity was analyzed in relation to clinicopathological variables and pre-treatment biomarkers. For cytotoxic drugs, SI-NETs demonstrated similar or higher sensitivity to 5-FU, platinum, gemcitabine and doxorubicin compared with CRC. For several of the targeted kinase inhibitors, SI-NET was among the most sensitive solid tumor types. CLL and ovarian cancer were generally the most sensitive tumor types to both cytotoxic drugs and protein kinase inhibitors. SI-NET was more sensitive to the mTOR inhibitor sirolimus than the other solid tumor types tested. Individual SI-NET samples demonstrated great variability in ex vivo sensitivity for most drugs. Cross-resistance between different drugs also varied considerably, being higher among protein kinase inhibitors. Age, stage, grade, peritoneal carcinomatosis and extra-abdominal metastases as well as serum chromogranin A and urine 5-HIAA concentrations at diagnosis did not correlate to drug sensitivity ex vivo SI-NETs exhibit intermediate sensitivity ex vivo to cytotoxic and targeted drugs. Clinicopathological factors and currently used biomarkers are not clearly associated to ex vivo sensitivity, challenging these criteria for treatment decisions in SI-NET. The great variability in drug sensitivity calls for individualized selection of therapy.

Chemotherapy in NETs: When and how

The majority of neuroendocrine tumours (NETs) are well-differentiated tumours that follow an indolent course, in contrast to a minority of poorly differentiated neuroendocrine carcinomas (NECs) which exhibit an aggressive course and assocaited with an overall short survival. Although surgery is the only curative treatment for NETs it is not always feasible,necessitating the application of other therapies including chemotherapy. Streptozotocin (STZ)-based regimens have long been used for advanced or metastatic well-to-moderately differentiated (G1-G2) NETs, especially those originating from the pancreas (pNETs). In poorly differentiated grade 3 (G3) tumours, platinum-based chemotherapy is recommended as first-line therapy, albeit without durable responses. Although data for temozolomide (TMZ)-based chemotherapy are still evolving, this treatment may replace STZ-based regimens in pNETs due to its better tolerability and side effect profile. In addition, there is evidence that TMZ could also be used in the subgroup of well-differentiated G3 NETs. There is less clear-cut evidence of a benefit for chemotherapy in intestinal NETs, but still evolving data suggest that TMZ may be efficacious in particular patients. In lung and thymic carcinoids, chemotherapy is reserved for patients with progressive metastatic disease in whom other treatment options are unavailable. Overall, chemotherapy is indicated in patients who have progressed on first-line treatment with somatostatin analogues, have extensive tumour load or exhibit rapid growth following a period of follow-up, and/or have a high proliferative rate; it may occasionally can be used in a neo-adjuvant setting. Prospective randomised studies are awaited to substantiate the role of chemotherapy in the therapeutic algorithm of NETs along with other evolving treatments.