Nordic guidelines 2021 for diagnosis and treatment of gastroenteropancreatic neuroendocrine neoplasms

Peptide Receptor Radionuclide Therapy of Neuroendocrine Tumors: Agonist, Antagonist and Alternatives

Peptide receptor radionuclide therapy (PRRT) today is a well-established treatment strategy for patients with neuroendocrine tumors (NET). First performed already more than 30 years ago, PRRT was incorporated only in recent years into the major oncology guidelines, based on its proven efficacy and safety in clinical trials. Following the phase 3 NETTER-1 trial, which led to the final registration of the radiopharmaceutical Luthatera® for G1/G2 NET patients in 2017, the long-term results of the phase 3 NETTER-2 trial may pave the way for a new treatment option also for advanced G2/G3 patients as first-line therapy. The growing knowledge about the synergistic effect of combined therapies could also allow alternative (re)treatment options for NET patients, in order to create a tailored treatment strategy. The evolving thera(g)nostic concept could be applied for the identification of patients who might benefit from different image-guided treatment strategies. In this scenario, the use of dual tracer PET/CT in NET patients, using both [18F]F-FDG/[68Ga]Ga-DOTA-somatostatin analog (SSA) for diagnosis and follow-up, is under discussion and could also result in a powerful prognostic tool. In addition, alternative strategies based on different metabolic pathways, radioisotopes, or combinations of different medical approaches could be applied. A number of different promising "doors" could thus open in the near future for the treatment of NET patients - and the "key" will be thera(g)nostic!

A case of early-stage type 3 gastric neuroendocrine tumor in the upper body of the stomach: is endoscopic resection feasible?

Although gastric neuroendocrine tumors (NETs) are uncommon compared with gastric carcinomas, the incidence of NETs has been recently increasing. Gastric NETs are classified into three subgroups, and among these, gastrin-independent sporadic type 3 gastric NETs have a poor prognosis because of frequent lymph node or distant metastasis. We experienced a case of an early-stage type 3 gastric NET associated with lymphovascular and submucosal invasion. In a 54 year-old woman, esophagogastroduodenoscopy performed during a health screening identified an elevated lesion of the upper body of the stomach. The results of immunohistochemical analyses of endoscopic biopsy specimens obtained from the lesion were positive for chromogranin A and synaptophysin, indicating an NET. Because the patient's serum gastrin level was normal and she had no predisposing conditions for NET development, the tumor was diagnosed as a type 3 gastric NET. The patient underwent local resection of the tumor and regional lymph node dissection. The resected specimen indicated a diagnosis of type 3 gastric NET with invasion into the submucosa and lymphatic duct. This is an extremely rare case of an early-stage type 3 gastric NET. Our discussion provides insight into the pathogenesis and development of these tumors and the appropriate therapeutic strategy.

Molecular Classification of Gastrointestinal and Pancreatic Neuroendocrine Neoplasms: Are We Ready for That?

In the last two decades, the increasing availability of technologies for molecular analyses has allowed an insight in the genomic alterations of neuroendocrine neoplasms (NEN) of the gastrointestinal tract and pancreas. This knowledge has confirmed, supported, and informed the pathological classification of NEN, clarifying the differences between neuroendocrine carcinomas (NEC) and neuroendocrine tumors (NET) and helping to define the G3 NET category. At the same time, the identification genomic alterations, in terms of gene mutation, structural abnormalities, and epigenetic changes differentially involved in the pathogenesis of NEC and NET has identified potential molecular targets for precision therapy. This review critically recapitulates the available molecular features of digestive NEC and NET, highlighting their correlates with pathological aspects and clinical characteristics of these neoplasms and revising their role as predictive biomarkers for targeted therapy. In this context, the feasibility and applicability of a molecular classification of gastrointestinal and pancreatic NEN will be explored.

Hypoalbuminemia, but not derived neutrophil to lymphocyte ratio (dNLR), predicts overall survival in neuroendocrine tumours undergoing peptide receptor radionuclide therapy: A retrospective, cohort study of 557 patients

Several inflammation scores have shown association with survival outcomes for patients with neuroendocrine tumours (NET) treated with peptide receptor radionuclide therapy (PRRT). However, whether these scores add value to established prognostic factors remains unknown. In this retrospective, cohort study of 557 NET patients undergoing PRRT in a tertiary referral centre from 2005 to 2015, we examined inflammatory markers and scores previously associated with cancer outcomes, using Cox proportional hazard models and Akaike's information criterion. Lower albumin (hazard ratio [95% confidence interval], .91 [.87-.95] per unit), as well as higher C-reactive protein (CRP; 1.02 [1.01-1.02]), Glasgow Prognostic Score (GPS; 1 vs. 0: 1.67 [1.14-2.44], 2 vs. 0 3.60 [2.24-5.79]), CRP/albumin ratio (1.84 [1.43-2.37]) and platelet count (Plt) × CRP, but not white blood cell, neutrophil and thrombocyte counts or derived neutrophil to lymphocyte ratio (dNLR), were associated with shorter median overall survival (OS) in an adjusted analysis. The addition of parameters based on albumin and CRP, but not dNLR, to a base model including age, chromogranin A, the cell proliferation marker Ki-67, performance status, tumour site and previous treatments improved the predictive accuracy of the base model. In an exploratory analysis of patients with available erythrocyte sedimentation rate (ESR) and CRP, ESR emerged as the most powerful predictor. When added to a prognostic model for OS in NET patients treated with PRRT, most inflammation scores further improved the model. Albumin was the single marker adding most value to the set of established prognostic markers, whereas dNLR did not seem to improve the model's prognostic ability.

Treatment of poorly differentiated neuroendocrine carcinomas of rectum and anus with chemoradiotherapy: a single-centre evaluation

PURPOSE

Poorly differentiated neuroendocrine carcinoma (PDNEC) of the rectum and anus is a rare disease exhibiting aggressive biological behaviour, even if diagnosed early. Currently, there are no agreed standard treatment approaches and management of locally advanced (LA) and metastatic PDNEC usually follows treatments used in pulmonary neuroendocrine carcinomas because of the similarities with small cell lung cancer. The role of surgery in PDNEC is still debated and the benefit of chemoradiotherapy (CRT) is unknown. This report summarises the experiences of CRT application in anorectal PDNEC in a single Danish institution.

METHODS

All patients with PDNEC treated with concomitant CRT between May 2019 and January 2021 at a University hospital in Denmark were evaluated. Demographics, treatment and survival outcomes were collected and analysed.

RESULTS

Six patients were identified. Five patients received radiotherapy with 50.4 Gy/28 fractions, and four were eligible for curative resection after the CRT. Distant metastasis was observed in four patients at diagnosis. Two patients with synchronous liver metastases were treated with RFA, and one received a liver resection. The treatment was well tolerated with limited side effects. The median follow-up time was 17 months (range 10-36 months), and the median duration of response was 11.2 months (range 8.1 to 24.2 months). One patient achieved a complete response.

CONCLUSION

A multimodal treatment approach with CRT in advanced stages of PDNEC in a highly selected patient group is well tolerated and with a high chance of achieving local control and, combined with surgery, even complete response in a single case.

Gastroenteropancreatic neuroendocrine carcinoma tumor spheroid drug screen reveals vulnerability to tyrosyl-DNA phosphodiesterase 1 inhibitors

BACKGROUND

Gastroenteropancreatic neuroendocrine carcinomas are rare neoplasms with no effective treatments and poor prognosis. Few reliable preclinical models exist for the study of gastroenteropancreatic neuroendocrine carcinomas, limiting investigation of novel treatments. We used tumor spheroids from our recently established gastroenteropancreatic neuroendocrine carcinoma patient-derived xenograft models to systematically screen for compounds with diverse structures to identify potential new categories of therapeutic agents that can target gastroenteropancreatic neuroendocrine carcinomas.

METHODS

Tumor spheroids were derived from our NEC913 and NEC1452 gastroenteropancreatic neuroendocrine carcinoma patient-derived xenograft models. Gastroenteropancreatic neuroendocrine carcinoma spheroids were screened against a library of 885 compounds from the National Cancer Institute Diversity Set VII collection. Cell viability was measured via AlamarBlue assay. After identification of potential therapeutic compounds, synergy screening of a selected group with temozolomide and doxorubicin was performed, and these combinations were further analyzed for γH2AX and phosphorylated-ERK proteins.

RESULTS

We identified 16 compounds that inhibit over 75% of gastroenteropancreatic neuroendocrine carcinoma spheroid survival. Seven are inhibitors of tyrosyl-DNA phosphodiesterase 1, a DNA repair enzyme working closely with the topoisomerase I complex. When combined with temozolomide or doxorubicin, the tyrosyl-DNA phosphodiesterase 1 inhibitor cytarabine increased the cytotoxic effects of these drugs on NEC1452 cells which was further evidenced by increasing γH2AX and decreasing phosphorylated-ERK in combination treatment compared to temozolomide alone.

CONCLUSION

Both NEC913 and NEC1452 gastroenteropancreatic neuroendocrine carcinoma spheroid lines are useful preclinical models for drug testing. Our library screen revealed these gastroenteropancreatic neuroendocrine carcinoma spheroids are highly sensitive to a novel class of anti-cancer drugs that target nuclear genome stability.

Plasma tryptophan pathway metabolites quantified by liquid chromatography-tandem mass spectrometry as biomarkers in neuroendocrine tumor patients

A good and accessible biomarker is of great clinical value in neuroendocrine tumor (NET) patients, especially considering its frequently indolent nature and long-term follow-up. Plasma chromogranin A (CgA) and 5-hydroxyindoleacetic acid (5-HIAA) are currently used as biomarkers in NET, but their sensitivity and specificity are restricted. 5-HIAA is the main metabolite of serotonin, an important neurotransmitter of the tryptophan pathway. The aim of this study is to estabish a sensitive and accurate method for the quantification of tryptophan pathway metabolites in plasma. We further aimed to evaluate its utility as a clinical tool in NET disease. We obtained plasma samples from NET patients and healthy controls recruited from the University Hospital of North Norway, Tromsø. Samples were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and eight metabolites of the tryptophan pathway were quantified. We included 130 NET patients (72/130 small intestinal [SI] NET, 35/130 pancreatic NET, 23/130 other origin) and 20 healthy controls. In the SI-NET group, 26/72 patients presented with symptoms of carcinoid syndrome (CS). We found that combining tryptophan metabolites into a serotonin/kynurenine pathway ratio improved diagnostic sensitivity (92.3%) and specificity (100%) in detecting CS patients from healthy controls compared with plasma 5-HIAA alone (sensitivity 84.6%/specificity 100%). Further, a clinical marker based on the combination of plasma serotonin, 5-HIAA, and 5OH-tryptophan, increased diagnostic capacity identifying NET patients with metastasized disease from healthy controls compared with singular plasma 5-HIAA, serotonin, or CgA. In addition, this marker was positive in 61% of curatively operated SI-NET patients compared with only 10% of healthy controls (p < .001). Our results indicate that simultaneous quantification of several tryptophan metabolites in plasma, using LC-MS/MS, may represent a clinically useful diagnostic tool in NET disease.

Anatomy-based correction of kidney PVE on [Formula: see text] SPECT images

BACKGROUND

In peptide receptor radionuclide therapy (PRRT), accurate quantification of kidney activity on post-treatment SPECT images paves the way for patient-specific treatment. Due to the limited spatial resolution of SPECT images, the partial volume effect (PVE) is a significant source of quantitative bias. In this study, we aimed to evaluate the performance and robustness of anatomy-based partial volume correction (PVC) algorithms to recover the accurate activity concentration of realistic kidney geometries on [Formula: see text]Lu SPECT images recorded under clinical conditions.

METHODS

Based on the CT scan data from patients, three sets of fillable kidneys with surface-to-volume (S:V) ratios ranging from 1.5 to 2.8 cm-1, were 3D printed and attached in a IEC phantom. Quantitative [Formula: see text]Lu SPECT/CT acquisitions were performed on a GE Discovery NM CT 870 DR camera for the three modified IEC phantoms and for 6 different Target-To-Background ratios (TBRs: 2, 4, 6, 8, 10, 12). Two region-based (GTM and Labbé) and five voxel-based (GTM + MTC, Labbé + MTC, GTM + RBV, Labbé + RBV and IY) methods were evaluated with this data set. Additionally, the robustness of PVC methods to Point Spread Function (PSF) discrepancies, registration mismatches and background heterogeneity was evaluated.

RESULTS

Without PVC, the average kidney RCs across all TBRs ranged from 0.66 ± 0.05 (smallest kidney) to 0.80 ± 0.03 (largest kidney). For a TBR of 12, all anatomy-based method were able to recover the kidneys activity concentration with an error < 6%. All methods result in a comparable decline in RC restoration with decreasing TBR. The Labbé method was the most robust against PSF and registration mismatches but was also the most sensitive to background heterogeneity. Among the voxel-based methods, MTC images were less uniform than RBV and IY images at the outer edge of high uptake areas (kidneys and spheres).

CONCLUSION

Anatomy-based PVE correction allows for accurate SPECT quantification of the [Formula: see text]Lu activity concentration with realistic kidney geometries. Combined with recent progress in deep-learning algorithms for automatic anatomic segmentation of whole-body CT, these methods could be of particular interest for a fully automated OAR dosimetry pipeline with PVE correction.

Type 3 gastric neuroendocrine neoplasms: the rising promise of conservative endoscopic management

Gastric neuroendocrine neoplasms (g-NENs) are rare tumors arising from the gastric enterochromaffin-like cells. Recent data suggests an increased detection rate, attributed to more frequent esophagogastroduodenoscopies. While type 3 g-NENs were historically deemed aggressive, emerging research indicates potential for conservative management, especially endoscopic resection, in well-differentiated, small tumors. European guidelines now advocate for endoscopic intervention in selected cases, but North American guidelines remain more conservative. Key factors influencing outcomes are tumor size, grading, and depth of gastric wall infiltration. Endoscopic resection has shown promise for tumors confined to submucosal layers without lymphovascular invasion. Given the complexities, a multidisciplinary team approach is essential for management decisions. Current insights are largely based on retrospective studies, underscoring the need for prospective research to optimize endoscopic approaches.

Recurrence-Free Survival and Disease-Specific Survival in Patients with Pancreatic Neuroendocrine Neoplasms: A Single-Center Retrospective Study of 413 Patients

INTRODUCTION

The prognosis and impact of different prognostic factors in pancreatic neuroendocrine neoplasms (pNEN) remain controversial.

AIM

To investigate prognostic factors for recurrence-free survival and disease-specific survival in patients with pNEN, divided into three groups: patients undergoing surveillance (tumor size < 2 cm, group 1), patients followed after curative-intended surgery (group 2), and patients with unresectable disease or residual tumors after resection (group 3).

METHOD

A single-center retrospective study including consecutive patients over a 20-year period. Multivariate Cox regression analyses were performed to identify risk factors.

RESULTS

413 patients were included, with a mean (SD) age of 62 ± 14 years. In group 1 (n = 51), median (IQR) follow-up was 29 (21-34) months, and tumor size was 1.0 (0.8-1.4) cm. One progressed and had a tumor resection. In group 2 (n = 165), follow-up 59 (31-102) months, median tumor size 2 (1.2-3.4) cm, median Ki-67 index 5 (3-10)%, the 5-year recurrence rate was 21%. Tumor size (p < 0.001), Ki-67 index (p = 0.02), and location in the pancreatic head (p < 0.001) were independent risk factors. In group 3 (n = 197), follow-up 19 (6-46) months, median tumor size 4.2 (2.6-7.0) cm, Ki-67 index 17 (9-64)%, the median disease-specific survival was 22 (6-75) months-99 in NET G1; 54 in NET G2; 14 in NET G3; and 6 months in neuroendocrine carcinomas (NEC). Age (p = 0.029), plasma chromogranin A (p = 0.014), and proliferation, expressed by grade (p = 0.001) and Ki-67 index (p < 0.001), were risk factors.

CONCLUSION

Growth in pNET < 2 cm requiring surgery was observed in 1/51. Tumor size, Ki-67 index, and location in the head were prognostic factors for disease recurrence, while age, plasma chromogranin A, and proliferation predicted mortality in patients with unresectable disease or residual tumors after resection.

Phase II study of everolimus and temozolomide as first-line treatment in metastatic high-grade gastroenteropancreatic neuroendocrine neoplasms

BACKGROUND

The optimal treatment for metastatic high-grade gastroenteropancreatic (GEP) neuroendocrine neoplasms when Ki-67 ≤55% is unknown. A prospective multi-centre phase 2 study was performed to evaluate the efficacy and safety of everolimus and temozolomide as first-line treatment for these patients.

METHODS

Patients received everolimus 10 mg daily continuously and temozolomide 150 mg/m2 for 7 days every 2 weeks. Endpoints included response, survival, safety and quality of life (QoL). Histopathological re-evaluation according to the 2019 WHO classification was performed.

RESULTS

For 37 eligible patients, the primary endpoint with 65% disease control rate (DCR) at 6 months (m) was reached. The response rate was 30%, the median progression-free survival (PFS) 10.2 months and the median overall survival (OS) 26.4 months. Considering 26 NET G3 patients, 6 months DCR was 77% vs. 22% among nine NEC patients (p = 0.006). PFS was superior for NET G3 vs. NEC (12.6 months vs. 3.4 months, Log-rank-test: p = 0.133, Breslow-test: p < 0.001). OS was significantly better for NET G3 (31.4 months vs. 7.8 months, p = 0.003). Grade 3 and 4 toxicities were reported in 43% and 38%. QoL remained stable during treatment.

CONCLUSION

Everolimus and temozolomide may be a treatment option for selected GEP-NET G3 patients including careful monitoring. Toxicity did not compromise QoL.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov (NTC02248012).

Optimal surgical approach for digestive neuroendocrine neoplasia primaries: Oncological benefits versus short and long-term complications

The rising incidence and the accumulating prevalence of neuroendocrine neoplasia (NEN) in the population makes this a common, prevalent and a clinically relevant disease group. Surgical resection represents the only potentially curative treatment for digestive NENs. Thus, resection should in principle be considered for all patients with NEN, although taking the patients age, relevant comorbidity, and performance status into account for operability. Patients with insulinomas, NEN of the appendix and rectal NENs are usually cured by surgery alone. However, less than a third of patients are amendable to curative surgery alone at time of diagnosis. Furthermore, recurrence is common and may occur years after primary surgery, hence the long follow-up time recommended in most NENs (>10 years). As many patients with NENs present with locoregional or metastatic disease, there is considerable debate regarding the role of debulking surgery in these settings. However, good long-term survival can be achieved in a considerable proportion of patients, with 50-70% alive up to 10 years after surgery. Location and grade are the main determinants of long-term survival. Here we present considerations to surgery for primary neuroendocrine tumors in the digestive tract.

Potent molecular-targeted therapies for gastro-entero-pancreatic neuroendocrine carcinoma

Neuroendocrine neoplasms (NENs), which are characterized by neuroendocrine differentiation, can arise in various organs. NENs have been divided into well-differentiated neuroendocrine tumors (NETs) and poorly differentiated neuroendocrine carcinomas (NECs) based on morphological differentiation, each of which has a distinct etiology, molecular profile, and clinicopathological features. While the majority of NECs originate in the pulmonary organs, extrapulmonary NECs occur most predominantly in the gastro-entero-pancreatic (GEP) system. Although platinum-based chemotherapy is the main therapeutic option for recurrent or metastatic GEP-NEC patients, the clinical benefits are limited and associated with a poor prognosis, indicating the clinically urgent need for effective therapeutic agents. The clinical development of molecular-targeted therapies has been hampered due to the rarity of GEP-NECs and the paucity of knowledge on their biology. In this review, we summarize the biology, current treatments, and molecular profiles of GEP-NECs based on the findings of pivotal comprehensive molecular analyses; we also highlight potent therapeutic targets for future precision medicine based on the most recent results of clinical trials.

European Neuroendocrine Tumor Society (ENETS) 2023 guidance paper for gastroduodenal neuroendocrine tumours (NETs) G1-G3

The aim of the present guidance paper was to update the previous ENETS guidelines on well-differentiated gastric and duodenal neuroendocrine tumours (NETs), providing practical guidance for specialists in the diagnosis and management of gastroduodenal NETs. Type II gastric NETs, neuroendocrine carcinomas (NECs), and functioning duodenal NETs are not covered, since they will be discussed in other ENETS guidance papers.

Local disease control after stereotactic body radiotherapy in patients with neuroendocrine neoplasms: a cohort study

BACKGROUND

Neuroendocrine neoplasms represent a diverse group of malignancies. Anatomic origin, histology and aggressiveness vary extensively, from low-grade tumours with an indolent prognosis to highly aggressive conditions with poor outcome. Surgery, with a curative intent, is the standard of treatment when possible. Other treatment regimens include local treatment, or systemic therapy. The role of radiotherapy in treating neuroendocrine neoplasms is not yet established, but studies indicate that a high rate of local control can be achieved by high-dose radiotherapy. Stereotactic body radiotherapy (SBRT) is high dose of radiation delivered to a small volume. We aimed to investigate the one-year local control rate of SBRT in patients with neuroendocrine neoplasms.

MATERIAL AND METHODS

Patients with neuroendocrine neoplasms treated with SBRT between 2003 and 2021 were retrospectively identified. Patient characteristics and SBRT-details were collected by review of patient records and the radiotherapy planning charts. All types except for small cell lung cancer and brain metastases were allowed. The prescribed dose was 45-67.8 Gy in three fractions. Progression, both within the target-site and in other sites, was determined based on existing imaging reports. One-year local control rate and systemic control rate was calculated. Descriptive analyses of local response duration, progression-free survival and overall survival were performed.

RESULTS

Twenty-one patients were included. The one-year local control rate was 94%. Four of the patients had local progression. All patients receiving SBRT towards their primary tumour (n = 11) had a bronchopulmonary neuroendocrine neoplasm, and a one-year local control rate of 100%. In patients treated at a metastatic target, 80% developed systemic progression but the local control remained high.

CONCLUSION

Our study suggests that SBRT may offer a feasible and effective treatment of neuroendocrine neoplasms in selected cases. SBRT provides long-term local stability and may be useful in treating patients with localised disease not fit for surgery.

An Investigation of Lesion Detection Accuracy for Artificial Intelligence-Based Denoising of Low-Dose 64Cu-DOTATATE PET Imaging in Patients with Neuroendocrine Neoplasms

Frequent somatostatin receptor PET, for example, 64Cu-DOTATATE PET, is part of the diagnostic work-up of patients with neuroendocrine neoplasms (NENs), resulting in high accumulated radiation doses. Scan-related radiation exposure should be minimized in accordance with the as-low-as-reasonably achievable principle, for example, by reducing injected radiotracer activity. Previous investigations found that reducing 64Cu-DOTATATE activity to below 50 MBq results in inadequate image quality and lesion detection. We therefore investigated whether image quality and lesion detection of less than 50 MBq of 64Cu-DOTATATE PET could be restored using artificial intelligence (AI). Methods: We implemented a parameter-transferred Wasserstein generative adversarial network for patients with NENs on simulated low-dose 64Cu-DOTATATE PET images corresponding to 25% (PET25%), or about 48 MBq, of the injected activity of the reference full dose (PET100%), or about 191 MBq, to generate denoised PET images (PETAI). We included 38 patients in the training sets for network optimization. We analyzed PET intensity correlation, peak signal-to-noise ratio (PSNR), structural similarity index (SSIM), and mean-square error (MSE) of PETAI/PET100% versus PET25%/PET100% Two readers assessed Likert scale-defined image quality (1, very poor; 2, poor; 3, moderate; 4, good; 5, excellent) and identified lesion-suspicious foci on PETAI and PET100% in a subset of the patients with no more than 20 lesions per organ (n = 33) to allow comparison of all foci on a 1:1 basis. Detected foci were scored (C1, definite lesion; C0, lesion-suspicious focus) and matched with PET100% as the reference. True-positive (TP), false-positive (FP), and false-negative (FN) lesions were assessed. Results: For PETAI/PET100% versus PET25%/PET100%, PET intensity correlation had a goodness-of-fit value of 0.94 versus 0.81, PSNR was 58.1 versus 53.0, SSIM was 0.908 versus 0.899, and MSE was 2.6 versus 4.7. Likert scale-defined image quality was rated good or excellent in 33 of 33 and 32 of 33 patients on PET100% and PETAI, respectively. Total number of detected lesions was 118 on PET100% and 115 on PETAI Only 78 PETAI lesions were TP, 40 were FN, and 37 were FP, yielding detection sensitivity (TP/(TP+FN)) and a false discovery rate (FP/(TP+FP)) of 66% (78/118) and 32% (37/115), respectively. In 62% (23/37) of cases, the FP lesion was scored C1, suggesting a definite lesion. Conclusion: PETAI improved visual similarity with PET100% compared with PET25%, and PETAI and PET100% had similar Likert scale-defined image quality. However, lesion detection analysis performed by physicians showed high proportions of FP and FN lesions on PETAI, highlighting the need for clinical validation of AI algorithms.

Prospective Phase II Trial of [68Ga]Ga-NODAGA-E[c(RGDyK)]2 PET/CT Imaging of Integrin αvβ3 for Prognostication in Patients with Neuroendocrine Neoplasms

Integrin α_vβ₃, a subtype of the arginine-glycine-aspartate (RGD)-recognizing cell surface integrins, is upregulated on endothelial cells during angiogenesis and on tumor cells. Because of involvement in tumor growth, invasiveness and metastases, and angiogenesis, integrin α_vβ₃ is an attractive target in cancers. In this study, we applied ⁶⁸Ga-NODAGA-E[c(RGDyK)]₂ for imaging of integrin α_vβ₃ in patients with neuroendocrine neoplasms (NENs) and its potential use for prognostication. We hypothesized that ⁶⁸Ga-NODAGA-E[c(RGDyK)]₂ PET/CT would show tumor lesion uptake and that higher tumor lesion uptake was associated with a poorer prognosis. Methods: Between December 2017 and November 2020 we prospectively enrolled 113 patients with NEN of all grades (2019 World Health Organization classification) for ⁶⁸Ga-NODAGA-E[c(RGDyK)]₂ PET/CT. The scan was acquired 45 min after injection of 200 MBq of ⁶⁸Ga-NODAGA-E[c(RGDyK)]₂ Board-certified specialists in nuclear medicine and radiology analyzed the PET/CT measuring SUV_max in tumor lesions. Positive tumor lesions were defined as those with tumor-to-liver background ≥ 2. Maximal tumor SUV_max for each patient was used as a predictor of outcome. Patients were followed for at least 1 y to assess progression-free survival and overall survival. Results: Of 113 patients enrolled in the trial, 99 underwent ⁶⁸Ga-NODAGA-E[c(RGDyK)]₂ PET/CT, with 97 patients having evaluable lesions. The patients predominantly had small intestinal (64%) or pancreatic (20%) NEN and most had metastatic disease (93%). Most patients had low-grade tumors (78%), whereas 22% had high-grade tumors. During a median follow-up of 31 mo (interquartile range, 26-38 mo), 62 patients (64%) experienced disease progression and 25 (26%) patients died. In total, 76% of patients had positive tumor lesions, and of the patients with high-grade tumors 91% had positive tumor lesions. High integrin α_vβ₃ expression, defined as an SUV_max of at least 5.25, had a hazard ratio of 2.11 (95% CI, 1.18-3.78) and 6.95 (95% CI, 1.64-29.51) for progression-free survival and overall survival, respectively (P = 0.01 for both). Conclusion: Tumor lesion uptake of ⁶⁸Ga-NODAGA-E[c(RGDyK)]₂ was evident in patients with all grades of NEN. High uptake was associated with a poorer prognosis. Further studies are warranted to establish whether ⁶⁸Ga-NODAGA-E[c(RGDyK)]₂ PET/CT may become a prediction tool for identification of patients eligible for treatments targeting integrin α_vβ_3.

Case report: Metastatic pancreatic neuroendocrine tumour associated with portal vein thrombosis; successful management with subsequent pregnancies

BACKGROUND

Splanchnic vein thrombosis due to co-existing metastatic pancreatic neuroendocrine tumour (pNET) and JAK2V617F mutation is a rare condition.

CASE REPORT

Here we present a case of a young woman with complete remission of a non-functioning grade 2 pNET with unresectable liver metastases, coexisting with JAK2V617F mutation. Splenectomy and distal pancreatectomy were performed. Neither surgical removal, nor radiofrequency ablation of the liver metastases was possible. Therefore, somatostatin analogue (SSA) and enoxaparine were started. Peptide receptor radionuclide therapy (PRRT) was given in 3 cycles 6-8 weeks apart. Genetic testing revealed no multiple endocrine neoplasia type 1 (MEN-1) gene mutations. After shared decision making with the patient, she gave birth to two healthy children, currently 2 and 4 years old. On pregnancy confirmation, SSA treatment was interrupted and resumed after each delivery. Ten years after the diagnosis of pNET, no tumour is detectable by MRI or somatostatin receptor scintigraphy. PRRT followed by continuous SSA therapy, interrupted only during pregnancies, resulted in complete remission and enabled the patient to complete two successful pregnancies.

The NET G3 enigma: dealing with a “new” entity

Neuroendocrine neoplasms of the gastroenteropancreatic system (GEP-NENs) have historically been graded into well-differentiated neuroendocrine tumors (NETs) G 1 and 2 and undifferentiated neuroendocrine carcinomas (NEC) G3 according to the proliferative index Ki-67, with the latter being larger than 20% for G3 NENs. However, clinical and pathological findings have suggested G3 NENs to be heterogeneous, and the most recent World Health Organization (WHO) classification has further subdivided G3 NENs into NET G3 with differentiated features and a usually lower Ki-67 (20–55%) as opposed to undifferentiated NECs. Currently, however, no standard approach to patients with NET G3 has been defined. As opposed to NET G1/G2, application of somatostatin analogues is not recommended, and the response to platinum-based chemotherapy is inferior when compared to NEC. The objective of this short review is to summarize pathological characteristics as well as therapeutic data obtained in patients with NET G3.

Prospective Phase II Trial of Prognostication by 68Ga-NOTA-AE105 uPAR PET in Patients with Neuroendocrine Neoplasms: Implications for uPAR-Targeted Therapy

The clinical course for patients with neuroendocrine neoplasms (NENs) ranges from indolent to highly aggressive. Noninvasive tools to improve prognostication and guide decisions on treatment are warranted. Expression of urokinase plasminogen activator receptor (uPAR) is present in many cancer types and associated with a poor outcome. Therefore, using an in-house-developed uPAR PET tracer [⁶⁸Ga]Ga-NOTA-Asp-Cha-Phe-D-Ser-D-Arg-Tyr-Leu-Trp-Ser-OH (⁶⁸Ga-NOTA-AE105), we aimed to assess uPAR expression in NENs. We hypothesized that uPAR expression was detectable in a significant proportion of patients and associated with a poorer outcome. In addition, as uPAR-targeted radionuclide therapy has previously proven effective in preclinical models, the study would also indicate the potential for uPAR-targeted radionuclide therapy in NEN patients. Methods: In a prospective clinical phase II trial, we included 116 patients with NENs of all grades, of whom 96 subsequently had uPAR PET/CT performed with evaluable lesions. PET/CT was performed 20 min after injection of approximately 200 MBq of ⁶⁸Ga-NOTA-AE105. uPAR target-to-liver ratio was used to define lesions as uPAR-positive when lesion SUV_max-to-liver SUV_mean ratio was at least 2. Patients were followed for at least 1 y to assess progression-free and overall survival. Results: Most patients had small intestinal NENs (n = 61) and metastatic disease (n = 86). uPAR-positive lesions were seen in 68% (n = 65) of all patients and in 75% (n = 18) of patients with high-grade (grade 3) NENs. During follow-up (median, 28 mo), 59 patients (62%) experienced progressive disease and 28 patients (30%) died. High uPAR expression, defined as a uPAR target-to-liver ratio above median, had a hazard ratio of 1.87 (95% CI, 1.11-3.17) and 2.64 (95% CI, 1.19-5.88) for progression-free and overall survival, respectively (P < 0.05 for both). Conclusion: When ⁶⁸Ga-NOTA-AE105 PET was used to image uPAR in patients with NENs, uPAR-positive lesions were seen in most patients, notably in patients with both low-grade and high-grade NENs. Furthermore, uPAR expression was associated with a worse prognosis. We suggest that uPAR PET is relevant for risk stratification and that uPAR may be a promising target for therapy in patients with NENs.

A convolutional neural network for total tumor segmentation in [64Cu]Cu-DOTATATE PET/CT of patients with neuroendocrine neoplasms

Background

Segmentation of neuroendocrine neoplasms (NENs) in [⁶⁴Cu]Cu-DOTATATE positron emission tomography makes it possible to extract quantitative measures useable for prognostication of patients. However, manual tumor segmentation is cumbersome and time-consuming. Therefore, we aimed to implement and test an artificial intelligence (AI) network for tumor segmentation. Patients with gastroenteropancreatic or lung NEN with [⁶⁴Cu]Cu-DOTATATE PET/CT performed were included in our training (n = 117) and test cohort (n = 41). Further, 10 patients with no signs of NEN were included as negative controls. Ground truth segmentations were obtained by a standardized semiautomatic method for tumor segmentation by a physician. The nnU-Net framework was used to set up a deep learning U-net architecture. Dice score, sensitivity and precision were used for selection of the final model. AI segmentations were implemented in a clinical imaging viewer where a physician evaluated performance and performed manual adjustments.

Results

Cross-validation training was used to generate models and an ensemble model. The ensemble model performed best overall with a lesion-wise dice of 0.850 and pixel-wise dice, precision and sensitivity of 0.801, 0.786 and 0.872, respectively. Performance of the ensemble model was acceptable with some degree of manual adjustment in 35/41 (85%) patients. Final tumor segmentation could be obtained from the AI model with manual adjustments in 5 min versus 17 min for ground truth method, p < 0.01.

Conclusion

We implemented and validated an AI model that achieved a high similarity with ground truth segmentation and resulted in faster tumor segmentation. With AI, total tumor segmentation may become feasible in the clinical routine.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13550-022-00901-2.

Advances in the Diagnosis and Therapeutic Management of Gastroenteropancreatic Neuroendocrine Neoplasms (GEP-NENs)

Neuroendocrine neoplasms (NENs) are an increasingly common cause of neoplastic diseases. One of the largest groups of NENs are neoplasms localized to the gastroenteropancreatic system, which are known as gastroenteropancreatic NENs (GEP-NENs). Because of nonspecific clinical symptoms, GEP-NEN patient diagnosis and, consequently, their treatment, might be difficult and delayed. This situation has forced researchers all over the world to continue progress in the diagnosis and treatment of patients with GEP-NENs. Our review is designed to present the latest reports on the laboratory diagnostic techniques, imaging tests and surgical and nonsurgical treatment strategies used for patients with these rare neoplasms. We paid particular attention to the nuclear approach, the use of which has been applied to GEP-NEN patient diagnosis, and to nonsurgical and radionuclide treatment strategies. Recent publications were reviewed in search of reports on new strategies for effective disease management. Attention was also paid to those studies still in progress, but with successful results. A total of 248 papers were analyzed, from which 141 papers most relevant to the aim of the study were selected. Using these papers, we highlight the progress in the development of diagnostic and treatment strategies for patients with GEP-NENs.

Surgery in Patients with Gastro-Entero-Pancreatic Neuroendocrine Carcinomas, Neuroendocrine Tumors G3 and High Grade Mixed Neuroendocrine-Non-Neuroendocrine Neoplasms

OPINION STATEMENT

In the 2019 WHO guidelines, the classification of gastro-entero-pancreatic neuroendocrine neoplasms (GEP NEN) has changed from one being based on Ki-67 proliferation index alone to one that also includes tumor differentiation. Consequently, GEP NENs are now classified as well-differentiated neuroendocrine tumor (NET), NET G1 (Ki-67 <3%), NET G2 (Ki-67 3-20%) and NET G3 (Ki-67 >20%), and poorly differentiated neuroendocrine carcinoma (NEC) (Ki-67 >20%). It has been suggested that NET G3 should be treated as NET G2 with respect to surgery, while surgical management of NEC should be expanded from local disease to also include patients with advanced disease where curative surgery is possible. High grade mixed neuroendocrine-non-neuroendocrine neoplasms (MiNEN) have a neuroendocrine and a non-neuroendocrine component mostly with a poor prognosis. All studies evaluating the effect of surgery in NEC and MiNEN are observational and hold a risk of selection bias, which may overestimate the beneficial effect of surgery. Further, only a few studies on the effect of surgery in MiNEN exist. This review aims to summarize the data on the outcome of surgery in patients with GEP NET G3, GEP NEC and high grade MiNEN. The current evidence suggests that patients with NEN G3 and localized disease and NEN G3 patients with metastatic disease where curative surgery can be achieved may benefit from surgery. In patients with MiNEN, it is currently not possible to evaluate on the potential beneficial effect of surgery due to the low number of studies.

An update on the diagnosis of gastroenteropancreatic neuroendocrine neoplasms

Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) arise from neuroendocrine cells found throughout the gastrointestinal tract and islet cells of the pancreas. The incidence and prevalence of GEP-NENs have been increasing each year due to higher awareness, improved diagnostic modalities, and increased incidental detection on cross-sectional imaging and endoscopy for cancer screening and other conditions and symptoms. GEP-NENs are a heterogeneous group of tumors and have a wide range in clinical presentation, histopathologic features, and molecular biology. Clinical presentation most commonly depends on whether the GEP-NEN secretes an active hormone. The World Health Organization recently updated the classification of GEP-NENs to introduce a distinction between high-grade neuroendocrine tumors and neuroendocrine carcinomas, which can be identified using histology and molecular studies and are more aggressive with a worse prognosis compared to high-grade neuroendocrine tumors. As our understanding of the biology of GEP-NENs has grown, new and improved diagnostic modalities can be developed and optimized. Here, we discuss clinical features and updates in diagnosis, including histopathological analysis, biomarkers, molecular techniques, and radiology of GEP-NENs. We review established diagnostic tests and discuss promising novel diagnostic tests that are currently in development or require further investigation and validation prior to broad utilization in patient care.

Activity Dose Reduction in 64Cu-DOTATATE PET in Patients with Neuroendocrine Neoplasms: Impact on Image Quality and Lesion Detection Ability

PURPOSE

Patients with neuroendocrine neoplasms (NEN) engage in lifelong follow-up with frequent somatostatin receptor PET, e.g. [⁶⁴Cu]Cu-DOTATATE PET, and continued measures to reduce radiation exposures should be in pursued in accordance with the as-low-as-reasonably-achievable (ALARA) principle. We therefore aimed to determine the lowest achievable [⁶⁴Cu]Cu-DOTATATE dose while maintaining image quality and lesion detection rate.

PROCEDURES

We included scans from 38 patients with NEN referred to routine [⁶⁴Cu]Cu-DOTATATE PET/CT. Using reconstruction of under-sampled PET list-mode data, we simulated [⁶⁴Cu]Cu-DOTATATE activity dose-reduced PET equivalents with median [range] 142 MBq [127;157], 95 MBq [85;105], and 48 MBq [42;52], corresponding to 75% (PET_75%), 50% (PET_50%), and 25% (PET_25%) of the full-dose 191 MBq [169;209] (PET_100%). Three blinded readers independently assessed image quality (scores 1-5), lesion confidence (scores 0-2), and counted lesions grouped by organs and regions. Number of lesions, proportions of patients with diagnostic image quality (reader-median image quality ≥ 4), diagnostic lesion confidence (reader-median lesion confidence ≥ 1), and per-patient sensitivities and specificities for organ-specific disease on PET_75-25% were compared with PET_100%.

RESULTS

The median [⁶⁴Cu]Cu-DOTATATE activity dose could be reduced from 191 to 142 MBq without decline in diagnostic image quality (P = 0.62), diagnostic lesion confidence (P = 1.0), or number of lesions detected in major organs or regions (P = 0.19-0.71). Sensitivity and specificity for detection of liver disease were 100% (26/26 patients) and 100% (12/12), respectively, for both PET_75% and PET_50%. Overall sensitivity for detection of NEN was 100% (26/26) for both PET_75% and PET_50%, and overall specificities were 92% (11/12) and 100% (12/12) for PET₇₅ and PET₅₀, respectively. Following dose-blinded post hoc review, the PET_75% specificity was adjusted to 100% (12/12).

CONCLUSIONS

The [⁶⁴Cu]Cu-DOTATATE activity dose can be reduced from 191 MBq to at least 142 MBq without losing image quality or lesion detection ability and further reduced to 95 MBq without loss of clinically relevant information.

Clinical and Molecular Characteristics of Rare Malignant Tumors of Colon and Rectum

Simple Summary

Tumors of colon and rectum other than adenocarcinomas represent a neglected issue from clinical and laboratory points of view because of their rarity. In this review, we summarize and describe the rare histologic entities occurring in colon and rectum. Clinical and pathologic characteristics, prognostic behavior, treatments, and altered genes are reported to provide readers with a paramount and comparative perspective. In relation to this, we propose that improvements in registries and multidisciplinary research are warranted to ameliorate their management.

Abstract

The most frequent form of colorectal cancer is represented by adenocarcinoma being about 98% of tumor histological types. However, other rare histotypes can be found in colon and rectum (adenosquamous, goblet cell adenocarcinoma, lymphoma, medullary carcinoma, melanoma, mesenchymal, neuroendocrine, plasmacytoma, signet ring, squamous tumors). Altogether, these forms account for less than 2% of colorectal tumors. There are no specific diagnostic or therapeutic recommended approaches and most of the information available from literature derives from small and retrospective clinical series. In the present study, we provide a paramount and updated view on clinical and biologic characteristics of rare colorectal tumors.

Role of Somatostatin Signalling in Neuroendocrine Tumours

Somatostatin (SST) is a small peptide that exerts inhibitory effects on a wide range of neuroendocrine cells. Due to the fact that somatostatin regulates cell growth and hormone secretion, somatostatin receptors (SSTRs) have become valuable targets for the treatment of different types of neuroendocrine tumours (NETs). NETs are a heterogeneous group of tumours that can develop in various parts of the body, including the digestive system, lungs, and pituitary. NETs are usually slow growing, but they are often diagnosed in advanced stages and can display aggressive behaviour. The mortality rate of NETs is not outstandingly increased compared to other malignant tumours, even in the metastatic setting. One of the intrinsic properties of NETs is the expression of SSTRs that serve as drug targets for SST analogues (SSAs), which can delay tumour progression and downregulate hormone overproduction. Additionally, in many NETs, it has been demonstrated that the SSTR expression level provides a prognostic value in predicting a therapeutic response. Furthermore, higher a SSTR expression correlates with a better survival rate in NET patients. In recent studies, other epigenetic regulators affecting SST signalling or SSA–mTOR inhibitor combination therapy in NETs have been considered as novel strategies for tumour control. In conclusion, SST signalling is a relevant regulator of NET functionality. Alongside classical SSA treatment regimens, future advanced therapies and treatment modalities are expected to improve the disease outcomes and overall health of NET patients.

Practical kidney dosimetry in peptide receptor radionuclide therapy using [177Lu]Lu-DOTATOC and [177Lu]Lu-DOTATATE with focus on uncertainty estimates

Background

Kidney dosimetry after peptide receptor radionuclide therapy using ¹⁷⁷Lu-labelled somatostatin analogues is a procedure with multiple steps. We present the SPECT/CT-based implementation at Aarhus University Hospital and evaluate the uncertainty of the various steps in order to estimate the total uncertainty and to identify the major sources of uncertainty. Absorbed dose data from 115 treatment fractions are reported.

Results

The total absorbed dose with uncertainty is presented for 59 treatments with [¹⁷⁷Lu]Lu-DOTATOC and 56 treatments with [¹⁷⁷Lu]Lu-DOTATATE. For [¹⁷⁷Lu]Lu-DOTATOC the mean and median specific absorbed dose (dose per injected activity) is 0.37 Gy/GBq and 0.38 Gy/GBq, respectively, while for [¹⁷⁷Lu]Lu-DOTATATE the median and mean are 0.47 Gy/GBq and 0.46 Gy/GBq, respectively. The uncertainty of the procedure is estimated to be about 13% for a single treatment fraction, where the absorbed dose calculation is based on three SPECT/CT scans 1, 4 and 7 days post-injection, while it increases to about 19% if only a single SPECT/CT scan is performed 1 day post-injection.

Conclusions

The specific absorbed dose values obtained with the described procedure are comparable to those from other treatment sites for both [¹⁷⁷Lu]Lu-DOTATOC and [¹⁷⁷Lu]Lu-DOTATATE, but towards the lower end of the range of reported values. The estimated uncertainty is also comparable to that from other reports and judged acceptable for clinical and research use, thus proving the kidney dosimetry procedure a useful tool. The greatest reduction in uncertainty can be obtained by improved activity determination, partial volume correction and additional SPECT/CT scans.