Radiolabelled somatostatin analogue treatment in gastroenteropancreatic neuroendocrine tumours: factors associated with response and suggestions for therapeutic sequence

Efficacy and tolerability of somatostatin analogues according to gender in patients with neuroendocrine tumors

As the incidence of neuroendocrine tumors has been rising, gender differences in epidemiology and clinical behavior have emerged, and interest into a gender-driven management of these tumors has grown with the aim to improve survival and quality of life of these patients. Somatostatin Analogues represent the first line of systemic treatment of both functional and non-functional neuroendocrine tumors, through the expression of somatostatin receptors (SSTRs) in the tumor cells, and proved effective in controlling hormonal hypersecretion and inhibiting tumor growth, improving progression-free survival and overall survival of these patients. Aim of the present review is to investigate any differences by gender in efficacy and safety of SSTS-targeted therapies, that represent the mainstay treatment of neuroendocrine tumors, as they emerge from studies of varying design and intent. Although preclinical studies have provided evidence in favor of differences by gender in tumor expression of SSTR, as well as of the role of sex hormones and related receptors in modulating SSTRs expression and function, the clinical studies conducted so far have not shown substantial differences between males and females in either efficacy or toxicity of SSTR-targeted therapies, even if with sometimes inconsistent results. Moreover, in most studies gender was not a predictor of response to treatment. Studies specifically designed to address this issue are needed to develop gender-specific therapeutic algorithms, improving patients' prognosis and quality of life.

Radioligand therapy (RLT) as neoadjuvant treatment for inoperable pancreatic neuroendocrine tumors: a literature review

In the last 10 years, several literature reports supported radioligand therapy (RLT) in neoadjuvant settings for pancreatic neuroendocrine tumors (PanNETs). Indeed, primary tumor shrinkage has been frequently reported following RLT in unresectable or borderline resectable PanNETs. Moreover, RLT-induced intratumoral modifications facilitate surgery, both on primary tumor and metastasis, having a great impact on progression free survival (PFS), overall survival (OS) and quality of life (QoL). However, prospective controlled investigations are necessary to confirm preliminary data and to define the best RLT scheme and the ideal patient that, in a multidisciplinary approach, should be referred to neoadjuvant RLT.

Factors Contributing to Tumor Shrinkage after Peptide Receptor Radionuclide Therapy in Patients with Unresectable Neuroendocrine Tumors

Peptide receptor activation therapy (PRRT) is a promising treatment option for metastatic neuroendocrine tumors (NETs). However, predicting tumor shrinkage before treatment is challenging. We analyzed the shrinkage rate of each metastatic tumor lesion to identify predictive factors related to shrinkage. Patients with metastatic NET who underwent PRRT were included in this retrospective study. For each patient, between one to five metastatic lesions were selected in descending order of size, and the change in the maximum tumor diameter after treatment was defined as the shrinkage rate per lesion (L-SR). We analyzed the relationship between pretreatment clinicopathological factors and L-SR. The median L-SR of all 75 lesions in 20 patients was 20% (95% CI: 4.8−26.1%). While previous treatment with cytotoxic agents (34.4%, p < 0.05) and primary tumor of the pancreas (27.8%, p < 0.05) were significantly favorable factors, a primary tumor of the rectum was significantly more resistant to shrinkage (−20.5%, p < 0.001). Therefore, lesion-based analysis of PRRT for NETs showed that pancreatic NET and previous treatment with cytotoxic agents were favorable factors for tumor shrinkage; however, rectal NET was a factor associated with resistance to shrinkage.

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.

Peptide Receptor Radionuclide Therapy Targeting the Somatostatin Receptor: Basic Principles, Clinical Applications and Optimization Strategies

Simple Summary

Peptide receptor radionuclide therapy (PRRT) is a systemic treatment consisting of the administration of a tumor-targeting radiopharmaceutical into the circulation of a patient. The radiopharmaceutical will bind to a specific peptide receptor leading to tumor-specific binding and retention. This will subsequently cause lethal DNA damage to the tumor cell. The only target that is currently used in widespread clinical practice is the somatostatin receptor, which is overexpressed on a range of tumor cells, including neuroendocrine tumors and neural-crest derived tumors. Academia played an important role in the development of PRRT, which has led to heterogeneous literature over the last two decades, as no standard radiopharmaceutical or regimen has been available for a long time. This review focuses on the basic principles and clinical applications of PRRT, and discusses several PRRT-optimization strategies.

Abstract

Peptide receptor radionuclide therapy (PRRT) consists of the administration of a tumor-targeting radiopharmaceutical into the circulation of a patient. The radiopharmaceutical will bind to a specific peptide receptor leading to tumor-specific binding and retention. The only target that is currently used in clinical practice is the somatostatin receptor (SSTR), which is overexpressed on a range of tumor cells, including neuroendocrine tumors and neural-crest derived tumors. Academia played an important role in the development of PRRT, which has led to heterogeneous literature over the last two decades, as no standard radiopharmaceutical or regimen has been available for a long time. This review provides a summary of the treatment efficacy (e.g., response rates and symptom-relief), impact on patient outcome and toxicity profile of PRRT performed with different generations of SSTR-targeting radiopharmaceuticals, including the landmark randomized-controlled trial NETTER-1. In addition, multiple optimization strategies for PRRT are discussed, i.e., the dose–effect concept, dosimetry, combination therapies (i.e., tandem/duo PRRT, chemoPRRT, targeted molecular therapy, somatostatin analogues and radiosensitizers), new radiopharmaceuticals (i.e., SSTR-antagonists, Evans-blue containing vector molecules and alpha-emitters), administration route (intra-arterial versus intravenous) and response prediction via molecular testing or imaging. The evolution and continuous refinement of PRRT resulted in many lessons for the future development of radionuclide therapy aimed at other targets and tumor types.

PRRT: identikit of the perfect patient

Peptide receptor radionuclide therapy (PRRT) has been strengthened since the publication of NETTER-1. Nevertheless, the correct positioning in the therapeutic algorithm is debated, and no optimal sequence has yet been standardized. Possible criteria to predict the response to PRRT in neuroendocrine tumors (NET) have been proposed. The aim of this review is to define the perfect identity of the eligible patient who can mostly benefit from this therapy. Possible predictive criteria which have been analysed were: primary tumor site, grading, tumor burden, FDG PET and ⁶⁸Ga-PET uptake. Primary tumor site and ⁶⁸Ga-PET uptake do not play a pivotal role in predicting the response, while tumor burden, FDG PET uptake and grading seem to represent predictive/prognostic factors for response to PRRT. The heterogeneity in trial designs, patient populations, type of radionuclides, previous therapies and measurement of outcomes, inevitably limits the strength of our conclusions, therefore care must be taken in applying these results to clinical practice. In conclusion, the perfect patient, selected by ⁶⁸Ga-PET uptake, will likely have a relatively limited liver tumor burden, a ki67 index <20% and will respond to PRRT irrespective to primary tumor. Nevertheless, we have mostly prognostic than predictive factors to predict the efficacy of PRRT in individual patients, while a promising tool could be the NETest. However, to date, the identikit of the perfect patient for PRRT is a puzzle without some pieces and still we cannot disregard a multidisciplinary discussion of the individual case to select the patients who will mostly benefit from PRRT.

Prior Resection of the Primary Tumor Prolongs Survival After Peptide Receptor Radionuclide Therapy of Advanced Neuroendocrine Neoplasms

OBJECTIVE

The aim of the study was to compare impact on survival after resection of primary tumors (PTs) after peptide receptor radionuclide therapy (PRRT).

BACKGROUND

PRRT is a highly effective therapeutic option to treat locally advanced or metastatic neuroendocrine neoplasms (NENs).

METHODS

We retrospectively analyzed the data of 889 patients with advanced NEN (G1-G3, stage IV) treated with at least 1 cycle of PRRT. In 486 of 889 patients (55%, group 1), PT had been removed before PRRT. Group 2 constituted 403 patients (45%) with no prior PT resection. Progression-free survival (PFS) and overall survival (OS) was determined by 68Ga SSTR-PET/CT in all patients applying RECIST and EORTC.

RESULTS

Most patients had their PT in pancreas (n = 335; 38%) and small intestine (n = 284; 32%). Both groups received a mean of 4 cycles of PRRT (P = 0.835) with a mean cumulative administered radioactivity of 21.6 ± 11.7 versus 22.2 ± 11.2 GBq (P = 0.407). Median OS in group 1 was 134.0 months [confidence interval (CI): 118-147], whereas OS in group 2 was 67.0 months (CI: 60-80; hazard ratio 2.79); P < 0.001. Likewise, the median progression-free survival after first PRRT was longer in group 1 with 18.0 (CI: 15-20) months as compared to group 2 with 14.0 (CI: 15-18; hazard ratio 1.21) months; P = 0.012.

CONCLUSIONS

A previous resection of the PT before PRRT provides a significant survival benefit in patients with NENs stage IV.

Current status of medical treatment for gastroenteropancreatic neuroendocrine neoplasms and future perspectives

Neuroendocrine neoplasms (NENs) constitute a heterogeneous group of tumors. In this review, we summarize the results of various clinical trials that have been conducted to investigate the efficacy and safety of various therapeutic options for NENs. Based on the encouraging results obtained from these trials, various therapeutic options have been established for the treatment of NENs, including somatostatin analogs (SSAs), molecularly targeted drugs and cytotoxic agents. In addition, peptide receptor radionucleotide therapy has recently been evaluated for the treatment of various NENs. We also discuss the approach for selecting the appropriate drugs and sequence of treatment with the various drug classes, as recommended by different treatment guidelines. Finally, we discuss the scope for future research in this field, especially into the merits of combination therapy with molecularly targeted drugs plus SSAs, along with ongoing studies.

Peptide Receptor Radionuclide Therapy of Pulmonary Neuroendocrine Neoplasms: a Single-Centre Experience

Purpose

Peptide receptor radionuclide therapy represents a therapeutic option for neuroendocrine neoplasms; to date, experiences with peptide receptor radionuclide therapy of pulmonary neuroendocrine neoplasms are still limited. We report our experience with peptide receptor radionuclide therapy of pulmonary neuroendocrine neoplasm patients.

Materials and Methods

Clinical records of 14 pulmonary neuroendocrine neoplasm patients (7 female and 7 male) who received at least 2 cycles of peptide receptor radionuclide therapy were retrospectively reviewed. Tumoural uptake of somatostatin analogues at pre-treatment imaging was graded as 2 to 3 in all patients. RECIST criteria were used to evaluate response.

Results

No treated patient had significant toxicity. Partial response was found in 3 (21.4%) patients, stable disease in 7 (50%), and progressive disease in 4 (28.6%). A statistically significant difference between disease state at enrolment and after peptide receptor radionuclide therapy was found.

Conclusions

Our data furtherly support peptide receptor radionuclide therapy as a safe and effective treatment of patients affected by pulmonary neuroendocrine neoplasms allowing disease control in about 71% of patients without showing significant toxicity. Other studies are needed to confirm our results.

Role of PET/CT and Therapy Management of Pancreatic Neuroendocrine Tumors

Pancreatic neuroendocrine neoplasms (panNENs) are heterogeneous neoplasms with neuroendocrine differentiation that show peculiar clinical and histomorphological features, with variable prognosis. In recent years, advances in knowledge regarding the pathophysiology and heterogeneous clinical presentation, as well as the availability of different diagnostic procedures for panNEN diagnosis and novel therapeutic options for patient clinical management, has led to the recognition of the need for an active multidisciplinary discussion for optimal patient care. Molecular imaging with positron emission tomography/computed tomography (PET/CT) has become indispensable for the management of panNENs. Several PET radiopharmaceuticals can be used to characterize either panNEN receptor expression or metabolism. The aim of this review is to offer an overview of all the currently used radiopharmaceuticals and of the new upcoming tracers for pancreatic neuroendocrine tumors (panNETs), and their clinical impact on therapy management. [68Ga]Ga-DOTA-peptide PET/CT (SSA-PET/CT) has high sensitivity, specificity, and accuracy and is recommended for the staging and restaging of any non-insulinoma well-differentiated panNEN cases to carry out detection of unknown primary tumor sites or early relapse and for evaluation of in vivo somatostatin receptors expression (SRE) to select patient candidates for peptide receptor radiometabolic treatment (PRRT) with 90Y or 177Lu and/or cold analogs. SSA-PET/CT also has a strong impact on clinical management, leading to a change in treatment in approximately a third of the cases. Its role for treatment response assessment is still under debate due to the lack of standardized criteria, even though some semiquantitative parameters seem to be able to predict response. [18F]FDG PET/CT generally shows low sensitivity in small growing and well-differentiated neuroendocrine tumors (NET; G1 and G2), while it is of utmost importance in the evaluation and management of high-grade NENs and also provides important prognostic information. When positive, [18F]FDG PET/CT impacts therapeutical management, indicating the need for a more aggressive treatment regime. Although FDG positivity does not exclude the patient from PRRT, several studies have demonstrated that it is certainly useful to predict response, even in this setting. The role of [18F]FDOPA for the study of panNET is limited by physiological uptake in the pancreas and is therefore not recommended. Moreover, it provides no information on SRE that has crucial clinical management relevance. Early acquisition of the abdomen and premedication with carbidopa may be useful to increase the accuracy, but further studies are needed to clarify its utility. GLP-1R agonists, such as exendin-4, are particularly useful for benign insulinoma detection, but their accuracy decreases in the case of malignant insulinomas. Being a whole-body imaging technique, exendin-PET/CT gives important preoperative information on tumor size and localization, which is fundamental for surgical planning as resection (enucleation of the lesion or partial pancreatic resection) is the only curative treatment. New upcoming tracers are under study, such as promising SSTR antagonists, which show a favorable biodistribution and higher tumor-to-background ratio that increases tumor detection, especially in the liver. [68Ga]pentixafor, an in vivo marker of CXCR4 expression associated with the behavior of more aggressive tumors, seems to only play a limited role in detecting well-differentiated NET since there is an inverse expression of SSTR2 and CXCR4 in G1 to G3 NETs with an elevation in CXCR4 and a decrease in SSTR2 expression with increasing grade. Other tracers, such as [68Ga]Ga-PSMA, [68Ga]Ga-DATA-TOC, [18F]SiTATE, and [18F]AlF-OC, are also under investigation.

Comparison of different calculation techniques for absorbed dose assessment in patient specific peptide receptor radionuclide therapy

Aim

The present work concerns the comparison of the performances of three systems for dosimetry in RPT that use different techniques for absorbed dose calculation (organ-level dosimetry, voxel-level dose kernel convolution and Monte Carlo simulations). The aim was to assess the importance of the choice of the most adequate calculation modality, providing recommendations about the choice of the computation tool.

Methods

The performances were evaluated both on phantoms and patients in a multi-level approach. Different phantoms filled with a ¹⁷⁷Lu-radioactive solution were used: a homogeneous cylindrical phantom, a phantom with organ-shaped inserts and two cylindrical phantoms with inserts different for shape and volume. A total of 70 patients with NETs treated by PRRT with ¹⁷⁷Lu-DOTATOC were retrospectively analysed.

Results

The comparisons were performed mainly between the mean values of the absorbed dose in the regions of interest. A general better agreement was obtained between Dose kernel convolution and Monte Carlo simulations results rather than between either of these two and organ-level dosimetry, both for phantoms and patients. Phantoms measurements also showed the discrepancies mainly depend on the geometry of the inserts (e.g. shape and volume). For patients, differences were more pronounced than phantoms and higher inter/intra patient variability was observed.

Conclusion

This study suggests that voxel-level techniques for dosimetry calculation are potentially more accurate and personalized than organ-level methods. In particular, a voxel-convolution method provides good results in a short time of calculation, while Monte Carlo based computation should be conducted with very fast calculation systems for a possible use in clinics, despite its intrinsic higher accuracy. Attention to the calculation modality is recommended in case of clinical regions of interest with irregular shape and far from spherical geometry, in which Monte Carlo seems to be more accurate than voxel-convolution methods.

Histopathological and Immunophenotypic Changes of Pancreatic Neuroendocrine Tumors after Neoadjuvant Peptide Receptor Radionuclide Therapy (PRRT)

Peptide Receptor Radionuclide Therapy (PRRT) is an emerging therapeutic option for pancreatic neuroendocrine tumors (PanNETs). A possible role for PRRT as a neoadjuvant agent is still largely undetermined, explored only in case reports or small case series. Likewise, the histopathological and immunophenotypic changes induced by PRRT are poorly characterized. In the present study, 24 patients who underwent neoadjuvant PRRT on the basis of their disease's characteristics were retrospectively matched with 24 patients who underwent upfront surgery. A comprehensive morphological and immunohistochemical evaluation was conducted to identify the differences in the two groups. The most significant findings were that the total percentage of stroma increased significantly in patients who underwent PRRT (p < 0.0001) and the characteristics of the stroma were different in the two groups. The somatostatin receptors type 2A (SSTR2A) were retained in most patients (87%) after PRRT. The density of CD163+ M2-polarized macrophages was greater in the PRRT group (p = 0.022), and M2-polarized macrophages tended to assume an epithelioid morphology (p = 0.043). In the neoadjuvant PRRT group, none of the histological parameters considered were associated with progression-free survival (PFS). Neoadjuvant PRRT in PanNETs is associated with reduced tumor diameter, an increased percentage of stroma, preserved SSTR2A expression in most of the cases, and an increased CD163+ M2-polarized macrophages density.

Peptide Receptor Radionuclide Therapy for the Treatment of Pancreatic Neuroendocrine Tumors: Recent Insights

Peptide receptor radionuclide therapy (PRRT) is a paradigm shifting approach to the treatment of neuroendocrine tumors. Although there are no prospective randomized trials directly studying PRRT in pancreatic neuroendocrine tumors (panNETs), there are data to suggest benefit in this patient population. Collectively, the data, consisting of two prospective and six retrospective studies, show a median PFS ranging from 20 to 39 months and a median OS ranging from 37 to 79 months. There are ongoing (and upcoming) prospective, randomized trials of PRRT in panNETs, which will provide further evidence to support this approach.

The North American Neuroendocrine Tumor Society Consensus Paper on the Surgical Management of Pancreatic Neuroendocrine Tumors

This manuscript is the result of the North American Neuroendocrine Tumor Society consensus conference on the surgical management of pancreatic neuroendocrine tumors from July 19 to 20, 2018. The group reviewed a series of questions of specific interest to surgeons taking care of patients with pancreatic neuroendocrine tumors, and for each, the available literature was reviewed. What follows are these reviews for each question followed by recommendations of the panel.

Efficacy of 177Lu Peptide Receptor Radionuclide Therapy for the Treatment of Neuroendocrine Tumors: A Meta-analysis

OBJECTIVE

The purpose of this study was to assess the efficacy of Lu-labeled peptide receptor radionuclide therapy (PRRT) induction treatments for patients with unresectable metastatic neuroendocrine tumors.

METHODS

MEDLINE, EMBASE, and Ovid were systematically searched with keywords "lutetium," "Lu-177," "PRRT," "neuroendocrine," and "prognosis." Studies evaluating treatment with Lu-labeled PRRT were assessed for disease response and/or disease control rate by Response Evaluation Criteria in Solid Tumors (RECIST) 1.0 or 1.1, modified RECIST, Southwest Oncology Group (SWOG), or modified SWOG criteria. Pooled proportions of disease response and control rates were calculated for both fixed- and random-effects models.

RESULTS

Eighteen studies with 1920 patients were included (11 with 1268 patients using RECIST and 6 with 804 patients using SWOG). By RECIST criteria, the pooled disease response rate by random-effects model was 29.1% (95% confidence interval [CI], 20.2%-38.9%), and disease control rate was 74.1% (95% CI, 67.8%-80.0%). By SWOG criteria, the pooled disease response rate by random-effects model was 30.6% (95% CI, 20.7%-41.5%), and disease control rate was 81.1% (95% CI, 76.4%-85.4%).

CONCLUSIONS

Induction therapy, typically 4 treatments, with Lu PRRT is an effective method of treating unresectable metastatic neuroendocrine tumors with significant disease response and control rates.

Neuroendocrine Tumor Therapy: 177Lu-DOTATATE

OBJECTIVE

The purposes of this article are to increase understanding of the concepts of theranostics and peptide receptor radionuclide therapy (PRRT) as they apply to neuroendocrine tumors (NETs); review the key 1, 2, and 3 clinical trial data leading to the approval of ¹⁷⁷Lu-tetraazacyclododecanetetraacetic acid-octreotide (¹⁷⁷Lu-DOTATATE); and foster understanding of the practical aspects and future directions of PRRT for NETs.

CONCLUSION

In January 2018, ¹⁷⁷Lu-DOTATATE therapy was approved in the United States (previously approved in Europe in September 2017) for adult patients with somatostatin receptor-positive gastroenteropancreatic neuroendocrine tumors, including those of the foregut, midgut, and hindgut. The results of the phase 3 Neuroendocrine Tumors Therapy (NETTER-1) trial show favorable outcomes with respect to the primary endpoint of progression-free survival and a host of secondary objectives, including overall survival, objective response rate, and quality of life measures. Patient selection is based on a number of specific factors and should be sequenced carefully with respect to other available therapies, ideally in multidisciplinary cancer conferences. Establishing the therapy at a new institution can be somewhat involved, but once it is established, the therapy is fairly straightforward to administer and is well tolerated with limited side-effects and toxicity. A number of approaches and issues are still to be worked out, and this therapy will continue to be studied and optimized.

Safety and Effectiveness of 177Lu-DOTATATE Peptide Receptor Radionuclide Therapy After Regional Hepatic Embolization in Patients With Somatostatin-Expressing Neuroendocrine Tumors

PURPOSE

Peptide receptor radionuclide therapy (PRRT) with Lu-DOTATATE is shown to be an effective therapeutic option for somatostatin-expressing neuroendocrine neoplasms. Some concerns are raised over safety of this modality in patients with a history of regional chemoembolization and radionuclide hepatic embolization (CRHE) and is cause of reluctance among some physicians for suggesting Lu-DOTATATE in this patient population.

METHODS

We retrospectively reviewed 143 patients with somatostatin-expressing neuroendocrine tumors who underwent Lu-DOTATATE PRRT. Statistical analysis was performed on effect of Lu-DOTATATE in patients with and without prior CRHE using resampling procedures and correlation coefficient (r).

RESULTS

Proportion of toxicity in patients with and without CRHE was comparable (P = 0.246). No statistically significant correlation (r) found between any toxicity and prior CRHE (r = -0.3 to -0.03) or time elapsed between embolization and the first cycle of PRRT (r = -0.59 to 0.17). Following PRRT, 76.5% of patients with CRHE experienced benefit (partial response + stable disease), whereas 23.4% experienced progressive disease. Patients with CRHE showed more stable disease (P = 0.048) and less progressive disease (P = 0.046) following PRRT compared with no CRHE. The CRHE and no-CRHE status shared same probability for developing partial response/complete response following PRRT (P = 0.50).

CONCLUSIONS

Treatment with Lu-DOTATATE did not show clinically or statistically significant toxicity in CRHE patients regardless of frequency of embolization or time interval between embolization and first PRRT. Results suggested a statistically significant higher response rate in patients with a history of CRHE. A prior history of CRHE is not a contraindication to subsequent PRRT.

Theranostics of Neuroendocrine Tumors

Somatostatin receptor positron emission tomography/computed tomography using ⁶⁸Ga-labeled somatostatin analogs is the mainstay for the evaluation of receptor status in neuroendocrine tumors (NETs). This translates towards better therapy options, with increasing evidence of peptide receptor radionuclide therapy (PRRT) as the treatment of choice for advanced or progressive NETs. There are benefits in progression-free and overall survival as well as a significant improvement in clinical condition. In patients with progressive NETs, fractionated, personalized PRRT results in good therapeutic responses with no significant severe hematological and/or renal toxicity, thus improving quality of life.

Neoadjuvant peptide receptor radionuclide therapy and modified multivisceral transplantation for an advanced small intestinal neuroendocrine neoplasm: an updated case report

Small intestinal neuroendocrine neoplasms (SI-NEN) frequently metastasise to regional lymph nodes, and surgery is the mainstay of therapy for such patients. However, despite the possible use of advanced surgical techniques, the resection of both primary and locoregional diseases is not always attainable. Intestinal and multivisceral transplantation has been performed in a small number of patients with conventionally nonresectable, slow-growing tumours threatening the mesenteric root but has remained controversial. The use of donor skin in “sentinel flaps” in transplantation theoretically offers advantages in tailoring immunosuppression and monitoring for rejection. We represent (with extended follow-up) the first case of a patient with inoperable extensive mesenteric metastases from SI-NEN, who underwent neoadjuvant peptide receptor radionuclide therapy before a modified multivisceral transplant with a concomitant vascularised sentinel forearm flap. At 48 months after transplantation, our patient remained at full physical activity with no evidence of disease recurrence on either tumour biochemistry or radiological imaging.

Real-world treatment patterns in advanced pancreatic neuroendocrine tumors in the era of targeted therapy: perspectives from an academic tertiary center and community oncology practices

Pancreatic neuroendocrine tumors (pNETs) are rare, slow-growing cancers. Optimal treatment of advanced pNETs is unclear. The aim of this study was to examine treatment patterns and preferences among an academic tertiary medical center and community-based oncology practices. Retrospective chart review was performed for patients with newly diagnosed locally advanced, metastatic, or unresectable pNET diagnosed between January 2010 and December 2013 at an academic tertiary cancer center [University of California, San Francisco (UCSF)] or a large network of community oncology practices [Altos Solutions' OncoEMR database (ALTOS)]. Fifty-four eligible patients (N _UCSF = 23; N _ALTOS = 31) were identified. Median time to treatment initiation was 1.1 months; median follow-up time was 22.9 months. UCSF patients underwent more lines of therapy than ALTOS patients despite similar follow-up times. UCSF tended toward more invasive treatment than ALTOS. The median time to treatment discontinuation was statistically significantly shorter for patients on chemotherapy than on targeted therapy in the combined UCSF and ALTOS groups (chemotherapy = 2.1 months vs. targeted = 18.6 months, p < 0.001). Treatment patterns and duration for newly diagnosed advanced pNETs vary widely both within and between different practice settings. Further studies are warranted to investigate the significant difference in duration of targeted therapy compared to chemotherapy.

Imaging approaches to assess the therapeutic response of gastroenteropancreatic neuroendocrine tumors (GEP-NETs): current perspectives and future trends of an exciting field in development

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are a family of neoplasms with a complex spectrum of clinical behavior. Although generally more indolent than carcinomas, once they progress beyond surgical resectability, they are essentially incurable. Systemic treatment options have substantially expanded in recent years for the management of advanced disease. Imaging plays a major role in new drug development, as it is the main tool used to objectively evaluate response to novel agents. However, current standard response criteria have proven suboptimal for the assessment of the antiproliferative effect of many targeted agents, particularly in the context of slow-growing tumors such as well-differentiated NETs. The aims of this article are to discuss the advantages and limitations of conventional radiological techniques and standard response assessment criteria and to review novel imaging modalities in development as well as alternative cancer- and therapy-specific criteria to assess drug efficacy in the field of GEP-NETs.

Metastatic Insulinoma Pancreatic Neuroendocrine Tumor Treated With 177Lu-DOTATATE Induction and Maintenance Peptide Receptor Radionuclide Therapy: A Suggested Protocol

A 70-year-old woman presented with frequent episodes of hypoglycemia. Imaging revealed a 6-cm pancreatic mass with several liver lesions. The pancreatic mass was resected and confirmed to be a well-differentiated insulinoma. Surgery improved but did not resolve her hypoglycemic episodes, and she was referred for peptide receptor radionuclide therapy with 177Lu-DOTATATE to treat her residual disease. A modified protocol with a continuous IV dextrose infusion was used, and the treatments were well tolerated. After 4 induction and 2 maintenance treatments, her hypoglycemic symptoms resolved completely and her disease stabilized. She has been progression free for 24 months.

Ectopic Corticotropin-Producing Neuroendocrine Tumor of the Pancreas Treated With 177Lu DOTATATE Induction and Maintenance Peptide Receptor Radionuclide Therapy

A 57-year-old woman diagnosed with ectopic Cushing syndrome was found to have a 111In-octreotide-avid corticotropin-producing pancreatic neuroendocrine tumor with liver metastases. She was treated with 4 induction and 4 maintenance cycles of 177Lu-DOTATATE, which normalized her serum corticotropin levels and dramatically reduced the size of the pancreatic primary and liver metastases.

Glucagonoma Pancreatic Neuroendocrine Tumor Treated With 177Lu DOTATATE Induction and Maintenance Peptide Receptor Radionuclide Therapy

A 56-year-old man presented with a history of 2 prior resections of a recurrent pancreatic glucagonoma in the past 4 years. Workup revealed new liver and abdominal nodal metastases with a rising serum glucagon level. He was started on peptide receptor radionuclide therapy with Lu DOTATATE, and his disease stabilized, while his glucagon levels decreased and also stabilized. After 4 induction and 2 maintenance cycles, he remains progression free for 23 months.

(177)Lu-labelled macrocyclic bisphosphonates for targeting bone metastasis in cancer treatment

Background

Metastatic bone lesion is a common syndrome of many cancer diseases in an advanced state. The major symptom is severe pain, spinal cord compression, and pathological fracture, associated with an obvious morbidity. Common treatments including systemic application of bisphosphonate drugs aim on pain reduction and on improving the quality of life of the patient. Particularly, patients with multiple metastatic lesions benefit from bone-targeting therapeutic radiopharmaceuticals. Agents utilizing beta-emitting radionuclides in routine clinical praxis are, for example, [⁸⁹Sr]SrCl₂ and [¹⁵³Sm]Sm-EDTMP. No-carrier-added (n.c.a.) ¹⁷⁷Lu is remarkably suitable for an application in this scope.

Methods

Five 1,4,7,10-tetraazacyclododecane N,N′,N′′,N′′-tetra-acetic acid (DOTA)- and DO2A-based bisphosphonates, including monomeric and dimeric structures and one 1,4,7-triazacyclononane-1,4-diacetic acid (NO2A) derivative, were synthesized and labelled with n.c.a. ¹⁷⁷Lu. Radio-TLC and high-performance liquid chromatography (HPLC) methods were successfully established for determining radiochemical yields and for quality control. Their binding to hydroxyapatite was measured in vitro. Ex vivo biodistribution experiments and dynamic in vivo single photon computed tomography (SPECT)/CT measurements were performed in healthy rats for 5 min and 1 h periods. Data on %ID/g or standard uptake value (SUV) for femur, blood, and soft-tissue organs were analyzed and compared with [¹⁷⁷Lu]citrate.

Results

Radiolabelling yields for [¹⁷⁷Lu]Lu-DOTA and [¹⁷⁷Lu]Lu-NO2A monomeric bisphosphonate complexes were >98 % within 15 min. The dimeric macrocyclic bisphosphonates showed a decelerated labelling kinetics, reaching a plateau after 30 min of 60 to 90 % radiolabelling yields. All ¹⁷⁷Lu-bisphosphonate complexes showed exclusive accumulation in the skeleton. Blood clearance and renal elimination were fast. SUV data (all for 1 h p.i.) in the femur ranged from 3.34 to 5.67. The bone/blood ratios were between 3.6 and 135.6, correspondingly. ¹⁷⁷Lu-bisphosphonate dimers showed a slightly higher bone accumulation (SUV_femur = 4.48 ± 0.38 for [¹⁷⁷Lu]Lu-DO2A(P^BP)₂; SUV_femur = 5.41 ± 0.46 for [¹⁷⁷Lu]Lu-DOTA(M^BP)₂) but a slower blood clearance (SUV_blood = 1.25 ± 0.09 for [¹⁷⁷Lu]Lu-DO2A(P^BP)₂; SUV_blood = 1.43 ± 0.32 for [¹⁷⁷Lu]Lu-DOTA(M^BP)₂).

Conclusions

Lu-complexes of macrocyclic bisphosphonates might become options for the therapy of skeletal metastases in the near future, since they show high uptake in bone together with a very low soft-tissue accumulation.

Is There an Additional Value of Using Somatostatin Receptor Subtype 2a Immunohistochemistry Compared to Somatostatin Receptor Scintigraphy Uptake in Predicting Gastroenteropancreatic Neuroendocrine Tumor Response?

BACKGROUND AND AIMS

It is unknown whether tumoral somatostatin receptor subtype 2a (sst2a) immunohistochemistry (IHC) has additional value compared to somatostatin receptor scintigraphy (SRS) uptake using OctreoScan® in predicting response to peptide receptor radiotherapy using 177Lu-octreotate (PRRT) in patients with gastroenteropancreatic neuroendocrine tumors (GEP-NETs). The aims of this study were: (1) to establish the percentage of sst2a immunopositivity in GEP-NET samples of PRRT-treated patients, (2) to determine the relationship between best GEP-NET response using RECIST 1.0 criteria 1 year after PRRT and tumoral sst2a IHC, and (3) to compare characteristics of patients with sst2a IHC-negative and -positive tumors.

METHODS

All 73 consecutive patients were selected for PRRT based on a positive SRS. Radiological response was scored according to RECIST 1.0 criteria. sst2a status was detected on tumor samples by IHC.

RESULTS

In total, 93% of GEP-NET samples showed sst2a IHC positivity. No statistically significant relationship was observed between in vitro sst2a expression and in vivo best GEP-NET response 1 year after PRRT (p = 0.47). Sex, primary tumor site, disease stage, ENETS TNM classification, Ki-67 index, highest serum chromogranin-A level, and highest neuron-specific enolase level were not significantly different between patients with negative and positive sst2a tumoral IHC with the exception of age at diagnosis (p = 0.007).

CONCLUSIONS

sst2a IHC of tumor samples has no additional value compared to SRS uptake using OctreoScan® in predicting tumor response after PRRT.

Radiation exposure to caregivers from patients undergoing common radionuclide therapies: a review

The contribution of radionuclide therapies (RNTs) to effective patient treatment is widely appreciated. The administration of high doses has necessitated investigating the potential radiation hazard to caregivers from patients undergoing RNTs. This work aimed to review the literature regarding measured effective doses to caregivers from such patients. The main selection criterion was the presence of real radiation exposure measurements. The results were categorised according to the treatment protocol and dose parameters. Analysis of the collected data demonstrated that the measured effective dose values were within the dose constraints defined by the International Commission on Radiological Protection, provided that the radiation protection instructions were followed by both patients and caregivers. In conclusion, the radiation risk for caregivers was almost negligible. In this context, treatments could be administered more often on an outpatient basis, once cost-effectiveness criteria were established and radiation protection training and procedures were appropriately applied.

The Challenges of Treating Paraganglioma Patients with (177)Lu-DOTATATE PRRT: Catecholamine Crises, Tumor Lysis Syndrome and the Need for Modification of Treatment Protocols

PURPOSE

A high percentage of paragangliomas express somatostatin receptors that can be utilized for targeted radioisotope therapy. The aim of this study was to describe and discuss the challenges of treating these tumors with (177)Lu-[DOTA(0),Tyr(3)]octreotate (DOTATATE) radioisotope therapy using established protocols.

METHODS AND RESULTS

Three paraganglioma patients were treated with 4-5 cycles of (177)Lu-DOTATATE and were evaluated for side effects and response to therapy. Two of the three patients developed severe adverse reactions following their first (177)Lu-DOTATATE treatment. One patient developed a catecholamine crisis and tumor lysis syndrome within hours of treatment, requiring intensive care unit (ICU) support, and another developed a catecholamine crisis 3 days after treatment, requiring hospitalization. The treatment protocols at our institution were subsequently modified by increasing the radioisotope infusion time from 15 to 30 min, as recommended in the literature, to 2-4 h and by reducing the administered dose of (177)Lu-DOTATATE. Subsequent (177)Lu-DOTATATE treatments utilizing the modified protocols were well tolerated, and response to therapy was achieved in all three patients, resulting in significantly improved quality of life.

CONCLUSION

(177)Lu-DOTATATE is an exciting new therapeutic option in the management of paragangliomas; however, current treatment protocols described in the literature may need to be modified by lengthening the infusion time and/or lowering the initial treatment dose to prevent or reduce the severity of adverse reactions.

Somatostatin receptors in bronchopulmonary neuroendocrine neoplasms: new diagnostic, prognostic, and therapeutic markers

CONTEXT AND OBJECTIVES

Gastroenteropancreatic neuroendocrine neoplasms are known for their overexpression of somatostatin receptors (SSTRs), which provide the molecular basis for diagnostic and therapeutic interventions. In contrast, few data on the SSTR expression profile exist for bronchopulmonary neuroendocrine neoplasms (BP-NEN).

DESIGN AND SETTINGS

A total of 240 formalin-fixed, paraffin-embedded specimens from 26 typical carcinoid (TC), 30 atypical carcinoid (AC), and 34 small cell lung cancer (SCLC) patients were examined retrospectively by immunohistochemistry (IHC) using specific rabbit monoclonal antibodies and evaluated by the immunoreactive score. Adjacent slides from 20 samples of each tumor type were subjected to additional RT-quantitative PCR mRNA analysis.

RESULTS

With different expression patterns, SSTRs were present in most of the tumor sections, at both the protein and mRNA levels. The RT-quantitative PCR data correlated with the IHC scores. SSTR1 was detected in approximately 65% of the TC and AC, but hardly in the SCLC, whereas both SSTR2A and SSTR5 were present in approximately 45% of each entity. Furthermore, the SSTR1 expression level was positively correlated with patient survival.

CONCLUSIONS

Our results suggest that SSTRs can be used as novel diagnostic, prognostic, and therapeutic markers of BP-NEN. The differences in the SSTR expression profile between the three types of BP-NEN may help to set a diagnostic cutoff and predict patient prognosis. Similar to TC and AC, our results also revealed a previously unappreciated high level of SSTR2A expression in SCLC within a subgroup of patients. However, in most cases, pan-somatostatin analogs may represent an additional therapeutic option.

Therapeutic strategies for neuroendocrine liver metastases

Patients who have neuroendocrine tumors frequently present with liver metastases. A wide panel of treatment options exists for these patients. Liver resection with curative intent achieves the best long-term results. Highly selected patients may be considered for liver transplantation. Substantial recurrence rates reported after surgical approaches call for neoadjuvant and adjuvant concepts. Liver-directed, locally ablative procedures are recommended for patients with limited, nonresectable tumor burden. Angiographic liver-directed techniques, such as transarterial embolization, transarterial chemoembolization, and selective internal radiotherapy, offer excellent palliation for patients with liver-predominant disease. Peptide receptor radionuclide therapy is a promising palliative procedure for patients with hepatic and/or extrahepatic metastases. The efficacy of these treatment options needs to be evaluated in randomized trials. Somatostatin analogues have demonstrated effectiveness not only for symptomatic relief in patients with secreting tumors but also for the control of proliferation in small intestinal neuroendocrine tumors and most recently also in those originating from the pancreas. Chemotherapy is an option mainly for those with pancreatic neuroendocrine tumors and high-grade tumors irrespective of the origin. Novel drugs targeting specific pathways within the tumor cell have produced improved progression-free survival compared with placebo in patients with pancreatic neuroendocrine tumors. Despite such a diverse armamentarium, there is uncertainty with regard to the optimal treatment regimens. Newly introduced molecular-based markers, along with the conduction of clinical trials comparing the efficacy of treatment modalities, offer a chance to move the treatment of neuroendocrine tumor disease toward personalized patient care. In this report, the authors review the approaches for treatment of neuroendocrine liver metastases, identify shortcomings, and anticipate future perspectives. Furthermore, clinical practice recommendations are provided for currently available treatment options. Although multiple modalities are available for the treatment of neuroendocrine liver metastases, optimal management is unclear. The current knowledge pertaining to these treatment options is analyzed.

PRRT: Defining the paradigm shift to achieve standardization and individualization

Peptide receptor radionuclide therapy is a treatment for inoperable or metastatic neuroendocrine tumors. A key issue is the need to standardize the treatment and develop randomized controlled trials. Standardization would help define the characteristics of response, including progression-free survival; provide homogeneous phase II and III studies; delineate the position of peptide receptor radionuclide therapy in the therapeutic algorithm for neuroendocrine tumors; and establish the basis for approval by the regulatory authorities. Standardization of treatments is the starting point to redefine the treatment paradigm from a one-size-fits-all to a personalized treatment. To delineate the treatment paradigm, treatments should be optimized for efficacy and minimization of long-term toxicity, through dosimetry, and adapted to each individual, including relevant patient characteristics. Although differences in therapy outcomes may be explained by the specific absorbed dose (or biologically effective dose), they may also be related to discrete tumor- and patient-specific features. In this respect, a particular area of investigation is the assessment of genetic elements regulating tumor cell proliferation, especially those involved in the response to cytotoxic therapies.

Management of patients with hepatic metastases from neuroendocrine tumors

Neuroendocrine tumors have a disposition toward metastasis to the liver. A range of treatment modalities for neuroendocrine liver metastases is available in the clinical arena, the indications for which depend on tumor characteristics such as patterns of metastasis, tumor grade, and anatomical origin. The complete surgical resection of liver deposits represents the only option with the intent to cure and is the gold standard approach, whereas cytoreductive resection (debulking) presents another surgical option aiming to ameliorate the symptoms and prolong survival. Liver transplantation is generally an accepted option for highly selected patients. For patients ineligible for radical surgery, liver-directed therapies-transarterial embolization/chemoembolization, selective internal radiotherapy, and local tumor ablation-present alternative strategies. Systemic therapies include peptide receptor radiotherapy, somatostatin analogues, cytotoxic chemotherapeutics, and novel molecularly targeted drugs. However, despite the variety of treatments available, there exists little evidence to guide optimal clinical practice with currently available data predominantly retrospective in nature. In this review, we discuss the diagnostic procedures that influence the trajectory of treatment of patients with neuroendocrine liver metastases before critically appraising the evidence pertaining to these therapeutic strategies.

Assessment of predictors of response and long-term survival of patients with neuroendocrine tumour treated with peptide receptor chemoradionuclide therapy (PRCRT)

PURPOSE

To review the response and outcomes of (177)Lu-DOTA-octreotate chemoradionuclide therapy (LuTate PRCRT) in patients with neuroendocrine tumour (NET) expressing high levels of somatostatin receptors with uncontrolled symptoms or disease progression.

METHODS

A total of 68 patients (39 men; 17 - 76 years of age) who had completed an induction course of at least three cycles of LuTate PRCRT between January 2006 and June 2010 were reviewed. Ten patients were treated for uncontrolled symptoms and 58 had disease progression despite conventional treatment. The majority had four induction LuTate cycles (median treatment duration 5 months and cumulative activity 31 GBq), and 63 patients had concomitant 5-FU radiosensitizing infusional chemotherapy. Factors predicting overall survival were assessed using the log-rank test and Cox proportional hazards regression.

RESULTS

Of those treated for uncontrolled symptoms, 70 % received benefit maintained for at least 6 months after treatment. Among patients with progressive disease 68 % showed stabilization or regression on CT, 67 % on molecular imaging and 56 % biochemically up to 12 months after treatment; 32 patients died. Overall survival rates at 2 and 5 year were 72.1 % and 52.1 %, respectively. Median overall survival was not estimable at a median follow-up of 60 months (range 5 - 86 months). Nonpancreatic primary sites, dominant liver metastases, lesion size <5 cm and the use of 5-FU chemotherapy were statistically significantly associated with objective response. A disseminated pattern and a high disease burden (whole-body retention index) were associated with an increased risk of death. Objective biochemical, molecular imaging and CT responses were all associated with longer overall survival.

CONCLUSION

A high proportion of patients with progressive NET or uncontrolled symptoms received therapeutic benefit from LuTate with concomitant 5-FU chemotherapy. The achievement of objective biochemical, molecular or CT responses within 12 months was associated with improved overall survival. Patients with a primary pancreatic site and larger lesions (>5 cm) appeared to have lower objective response rates and may need a more aggressive treatment approach.