Highly favourable outcomes with peptide receptor radionuclide therapy (PRRT) for metastatic rectal neuroendocrine neoplasia (NEN)

[Systemic treatment of patients with metastatic neuroendocrine Neoplasia]

Due to the complexity and heterogeneity of metastatic NEN an interdisciplinary expert team should be involved in an individualized treatment strategy. SSA is the mainstay of antisecretory treatment in most functioning tumors. In antiproliferative intention SSA are first line treatment in receptor positive low proliferative NET. In intestinal metastatic disease PRRT is best established second line treatment. Further options are Everolimus (labeled) and tyrosine kinase inhibitors (off-label). Everolimus is the only approved drug for antiproliferative treatment in patients with metastatic lung NET, whereas in pancreatic NET more therapeutic options are available (SSA, chemotherapy, PRRT, Sunitinib, Everolimus) without a standard of best sequence. In patients with metastatic NEC standard first line treatment (platinum + etoposide) has not changed for decades and new treatment options for this fatal disease are urgently needed. Benefit of immunotherapy is limited to a small subset of patients - new combinations are under investigation. This review summarizes the standard of care, criteria of treatment selection and new developments for systemic therapy in patients with metastatic NEN.

Role of FDG PET/CT in Management of Patients with Prostate Cancer

Prostate cancer is the second most common cancer in men worldwide. [18F]FDG PET/CT imaging, a well-known and effective technique for detecting malignancies, has not been considered a useful tool for prostate cancer imaging by many because of its perceived low [18F]FDG uptake. Incidentally detected focal [18F]FDG uptake in the prostate is not uncommon, and typically benign. Imaging features that would increase concern for an underlying prostatic carcinoma, include focal uptake in the periphery near the gland margin without calcifications. [18F]FDG PET/CT imaging provides little value in the initial staging of prostate cancer, particularly in the era of prostate specific membrane antigen (PSMA) radiotracer. In cases of biochemical recurrence, the value of [18F]FDG PET/CT increases notably when Grade group 4 or 5 and elevated PSA levels are present. Active research is underway for theranostic approaches to prostate cancer, including [177Lu]Lu-PSMA therapy. Dual tracer staging using FDG and PSMA imaging significantly enhances the accuracy of disease site assessment. Specifically, the addition of [18F]FDG PET/CT imaging allows for the evaluation of discordant disease (PSMA negative/FDG positive). The maximal benefit from [177Lu]Lu-PSMA therapy relies on significant PSMA accumulation across all disease sites, and the identification of discordant disease suggests that these patients may derive less benefit from the treatment. The genuine value of [18F]FDG PET/CT imaging lies in advanced prostate cancer, PSMA-negative disease, as a prognostic biomarker, and the realm of new targeted theranostic agents.

Targeted radionuclide therapy in endocrine-related cancers: advances in the last decade

Targeted radionuclide therapy plays an increasingly important role in managing endocrine-related tumors and significantly advances the therapeutic landscape for patients with these diseases. With increasing FDA-approved therapies and advances in the field, come an increased knowledge of the potential for long-term toxicities associated with these therapies and the field must develop new strategies to increase potency and efficacy while individualizing the selection of patients to those most likely to respond to treatment. Novel agents and modalities of therapy are also being explored. This review will discuss the current landscape and describe the avenues for growth in the field currently being explored.

Theranostic Nuclear Medicine with Gallium-68, Lutetium-177, Copper-64/67, Actinium-225, and Lead-212/203 Radionuclides

Molecular changes in malignant tissue can lead to an increase in the expression levels of various proteins or receptors that can be used to target the disease. In oncology, diagnostic imaging and radiotherapy of tumors is possible by attaching an appropriate radionuclide to molecules that selectively bind to these target proteins. The term "theranostics" describes the use of a diagnostic tool to predict the efficacy of a therapeutic option. Molecules radiolabeled with γ-emitting or β+-emitting radionuclides can be used for diagnostic imaging using single photon emission computed tomography or positron emission tomography. Radionuclide therapy of disease sites is possible with either α-, β-, or Auger-emitting radionuclides that induce irreversible damage to DNA. This Focus Review centers on the chemistry of theranostic approaches using metal radionuclides for imaging and therapy. The use of tracers that contain β+-emitting gallium-68 and β-emitting lutetium-177 will be discussed in the context of agents in clinical use for the diagnostic imaging and therapy of neuroendocrine tumors and prostate cancer. A particular emphasis is then placed on the chemistry involved in the development of theranostic approaches that use copper-64 for imaging and copper-67 for therapy with functionalized sarcophagine cage amine ligands. Targeted therapy with radionuclides that emit α particles has potential to be of particular use in late-stage disease where there are limited options, and the role of actinium-225 and lead-212 in this area is also discussed. Finally, we highlight the challenges that impede further adoption of radiotheranostic concepts while highlighting exciting opportunities and prospects.

The relationship between tumour dosimetry, response, and overall survival in patients with unresectable Neuroendocrine Neoplasms (NEN) treated with 177Lu DOTATATE (LuTate)

Peptide Receptor Radionuclide Therapy (PRRT) delivers targeted radiation to Somatostatin Receptor (SSR) expressing Neuroendocrine Neoplasms (NEN). We sought to assess the predictive and prognostic implications of tumour dosimetry with respect to response by 68 Ga DOTATATE (GaTate) PET/CT molecular imaging tumour volume of SSR (MITVSSR) change and RECIST 1.1, and overall survival (OS).

METHODS

Patients with gastro-entero-pancreatic (GEP) NEN who received LuTate followed by quantitative SPECT/CT (Q-SPECT/CT) the next day (Jul 2010 to Jan 2019) were retrospectively reviewed. Single time-point (STP) lesional dosimetry was performed for each cycle using population-based pharmacokinetic modelling. MITVSSR and RECIST 1.1 were measured at 3-months post PRRT.

RESULTS

Median of 4 PRRT cycles were administered to 90 patients (range 2-5 cycles; mean 27.4 GBq cumulative activity; mean 7.6 GBq per cycle). 68% received at least one cycle with radiosensitising chemotherapy (RSC). RECIST 1.1 partial response was 24%, with 70% stable and 7% progressive disease. Cycle 1 radiation dose in measurable lesions was associated with local response (odds ratio 1.5 per 50 Gy [95% CI: 1.1-2.0], p = 0.002) when adjusted by tumour grade and RSC. Median change in MITVSSR was -63% (interquartile range -84 to -29), with no correlation with radiation dose to the most avid lesion on univariable or multivariant analyses (5.6 per 10 Gy [95% CI: -1.6, 12.8], p = 0.133). OS at 5-years was 68% (95% CI: 56-78%). Neither baseline MITVSSR (hazard ratio 1.1 [95% CI: 1.0, 1.2], p = 0.128) nor change in baseline MITVSSR (hazard ratio 1.0 [95% CI: 1.0, 1.1], p = 0.223) were associated with OS when adjusted by tumour grade and RSC but RSC was (95% CI: 0.2, 0.8, p = 0.012).

CONCLUSION

Radiation dose to tumour during PRRT was predictive of radiologic response but not survival. Survival outcomes may relate to other biological factors. There was no evidence that MITVSSR change was associated with OS, but a larger study is needed.

European Neuroendocrine Tumor Society (ENETS) 2023 guidance paper for colorectal neuroendocrine tumours

This ENETS guidance paper, developed by a multidisciplinary working group, provides an update on the previous colorectal guidance paper in a different format. Guided by key clinical questions practical advice on the diagnosis and management of neuroendocrine tumours (NET) of the caecum, colon, and rectum is provided. Although covered in one guidance paper colorectal NET comprises a heterogeneous group of neoplasms. The most common rectal NET are often small G1 tumours that can be treated by adequate endoscopic resection techniques. Evidence from prospective clinical trials on the treatment of metastatic colorectal NET is limited and discussion of patients in experienced multidisciplinary tumour boards strongly recommended. Neuroendocrine carcinomas (NEC) and mixed neuroendocrine non-neuroendocrine neoplasms (MiNEN) are discussed in a separate guidance paper.

Rectal neuroendocrine neoplasms: what the radiologists should know

Neuroendocrine neoplasms of the rectum (R-NENs) are rare; however, their incidence has increased almost threefold in the last few decades. Imaging of R-NENs includes two primary categories: anatomic/morphologic imaging comprised of endoscopic ultrasound (EUS), computed tomography (CT), magnetic resonance imaging (MRI), and functional/molecular imaging comprising of planar scintigraphy, single-photon emission computed tomography (SPECT), and positron emission tomography (PET). The management depends on stage, dimension, atypical features, histological grade, and lymphovascular invasion (LVI). Low-risk local R-NENs can be resected endoscopically, and high-risk or locally advanced neoplasms can be treated with radical surgery and lymphadenectomy and/or chemoradiation. The review article focuses on imaging illustrations and discusses applications of different imaging modalities in diagnosing and managing R-NENs.

Diagnostic performance and impact on patient management of [68Ga]Ga-DOTA-TOC PET/CT in colorectal neuroendocrine tumors derived from hindgut

The main purpose of this retrospective study was to determine the diagnostic performance of [68Ga]Ga-DOTA-D-Phe1-Try3-octreotide(DOTA-TOC) positron emission tomography/computed tomography (PET/CT) in patients with well-differentiated colorectal Neuroendocrine Tumours (NETs) originating from the hindgut. The other aims were to assess the impact of the examination on patient management and to analyze the results of 2-[18F]FDG and/or 6-[18F]FDOPA PET/CT when they were performed. [68Ga]Ga-DOTA-TOC PET/CT and clinical data from 30 patients with biopsy-proven well-differentiated NETs originating from the hindgut were retrospectively reviewed and analyzed by comparing the [68Ga]Ga-DOTA-TOC PET/CT findings with pathological and/or follow-up data. We also compared the [68Ga]Ga-DOTA-TOC PET/CT results with 2-[18F]FDG and/or 6-[18F]FDOPA PET/CT results in 6 patients. The impact on management was determined in hindsight by comparing the patient management decided before and after the TEP examination based on data from multidisciplinary team meetings. On a patient basis, [68Ga]Ga-DOTA-TOC PET/CT was accurate in 30 of the 30 examinations. [68Ga]Ga-DOTA-TOC PET/CT correctly identified the primary tumor in all patients with primary tumors not resected before the examination and allowed the detection of unexpected distant metastases in 36% of the patients referred for initial staging. [68Ga]Ga-DOTA-TOC PET/CT findings affected patient management in 57% of cases with generally major intermodality changes. Intraindividual comparison of the results of the different PET radiopharmaceuticals showed a clear superiority of [68Ga]Ga-DOTA-TOC PET/CT considering both the number of lesions and the intensity of uptake. [68Ga]Ga-DOTA-TOC PET/CT is an accurate imaging modality for the assessment of well-differentiated colorectal NETs that highly impact patient management. Thus, we suggest that [68Ga]Ga-DOTA-TOC PET/CT be employed as a first choice for the assessment of these tumors in nuclear medicine.

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.

Toxicity and Tolerability of 177Lu-DOTA-TATE PRRT with a Modified Administered Activity Protocol in NETs of Variable Origin - A Phase 2 Registry Study

BACKGROUND

Peptide receptor radionuclide therapy (PRRT) has been recently approved for advanced, metastatic, or progressive neuroendocrine tumors (NETs).

OBJECTIVE

This study reports the adverse events (AEs) observed with patient-tailored administered activity.

METHODS

Fifty-two PRRT naive patients were treated with 177Lu-DOTATATE. The administered activity ranges between 2.78 and 5.55 GBq/cycle using the patient's unique characteristics (age, symptoms, blood work, and biomarkers).

RESULTS

The protocol was well tolerated with the overwhelming majority of participants being forty- six (88%), completing all 4 induction therapy cycles. The median cumulative administered activity was 19.6 GBq (ranged 3.8-22.3 GBq). A total of 42/52 (81%) reported at least one symptom, and 43/52 (83%) had evidence of biochemical abnormality at enrollment that would meet grade 1 or 2 criteria for AEs. These symptoms only slightly increase with treatment to 50/52 (96%) and 51/52 (98%), respectively. The most common symptoms were mild fatigue (62%), shortness of breath (50%), nausea (44%), abdominal pain (38%), and musculoskeletal pain (37%). The most common biomarker abnormalities were mild anemia (81%), reduced estimated glomerular filtration rate (eGFR) (58%), increased alkaline phosphatase (ALP) (50%), and leukopenia (37%). Of critical importance, no 177Lu-DOTATATE related grade 3 or 4 AEs were observed.

CONCLUSION

Tailoring the administered activity of 177Lu-DOTATATE to the individual patient with a variety of NETs is both safe and well-tolerated. No patient developed severe grade 3 or 4 AEs. Most patients exhibit symptoms or biochemical abnormality before treatment and this only slightly worsens following induction therapy.

Somatostatin and Its Receptor System in Colorectal Cancer

Somatostatin (SST)/somatotropin release-inhibiting factor (SRIF) is a well-known neuropeptide, widely distributed in the central and peripheral nervous systems, that regulates the endocrine system and affects neurotransmission via interaction with five SST receptors (SST1-5). In the gastrointestinal tract, the main SST-producing cells include intestinal enteroendocrine cells (EECs) restricted to the mucosa, and neurons of the submucosal and myenteric plexuses. The action of the SRIF system is based on the inhibition of endocrine and exocrine secretion, as well as the proliferative responses of target cells. The SST1–5 share common signaling pathways, and are not only widely expressed on normal tissues, but also frequently overexpressed by several tumors, particularly neuroendocrine neoplasms (NENs). Furthermore, the SRIF system represents the only peptide/G protein-coupled receptor (GPCR) system with multiple approved clinical applications for the diagnosis and treatment of several NENs. The role of the SRIF system in the histogenesis of colorectal cancer (CRC) subtypes (e.g., adenocarcinoma and signet ring-cell carcinoma), as well as diagnosis and prognosis of mixed adenoneuroendocrine carcinoma (MANEC) and pure adenocarcinoma, is poorly understood. Moreover, the impact of the SRIF system signaling on CRC cell proliferation and its potential role in the progression of this cancer remains unknown. Therefore, this review summarizes the recent collective knowledge and understanding of the clinical significance of the SRIF system signaling in CRC, aiming to evaluate the potential role of its components in CRC histogenesis, diagnosis, and potential therapy.

Multicenter Analysis of Presacral Neuroendocrine Neoplasms-Clinicopathological Characterization and Treatment Outcomes of a Rare Disease

Background and Aims

Neuroendocrine neoplasms (NENs) of the presacral space are an extremely rare disease entity with largely unknown outcome and no established standard of care treatment. Therefore, we wanted to analyze clinical presentation, histopathological findings, treatment outcomes, and prognosis in a multicentric patient cohort.

Methods

We searched local databases of six German NEN centers for patients with presacral NEN. Retrospective descriptive analyses of age, sex, stage at diagnosis, symptoms, grade, immunohistochemical investigations, biomarkers, treatment, and treatment outcome were performed. Kaplan-Meier analysis was used to determine median overall survival.

Results

We identified 17 patients (11 female, 6 male) with a median age of 50 years (range, 35-66) at diagnosis. Twelve cases presented initially with distant metastases including bone metastases in nine cases. On pathological review the majority of patients had well-differentiated G2 tumors. Immunohistochemical profile resembled rectal NENs. All but one patient had non-functioning tumors. Somatostatin receptor imaging was positive in 14 of 15 investigated cases. Eight patients were treated surgically including palliative resections; 14 patients received somatostatin analogs with limited efficacy. With 14 PRRTs completed, 79% showed clinical benefit, whereas only one patient with neuroendocrine carcinoma (NEC) responded to chemotherapy. Treatment with everolimus in three patients was not successful, whereas cabozantinib resulted in a disease stabilization in a heavily pretreated patient. During a median observation period of 44.5 months, 6 patients died. Median overall survival was not reached.

Conclusion

Presacral NEN are histopathologically similar to rectal NENs. Presacral NEN should be considered as possible primary in NEN of unknown primary. The majority of tumors is non-functioning and somatostatin receptor positive. PRRT demonstrated promising activity; tyrosine kinase inhibitors warrant further investigations. Further molecular characterization and prospective evaluation of this rare tumor entity are needed.

Theranostic implications of molecular imaging phenotype of well-differentiated pulmonary carcinoid based on 68Ga-DOTATATE PET/CT and 18F-FDG PET/CT

PURPOSE

This study aimed to analyse the molecular imaging (MI) phenotype of typical carcinoid (TC) and atypical carcinoid (AC) by ⁶⁸Ga-DOTATATE (GaTATE) and ¹⁸F-FDG (FDG) PET/CT with the emphasis on its potential theranostic implications for peptide receptor radionuclide therapy (PRRT).

METHODS

Retrospective review of patients with biopsy-proven TC or AC undergoing both GaTATE and FDG PET/CT at presentation. Based on correlative CT or MRI, positive lesions on either scan were defined by uptake above liver parenchyma. Per patient MI phenotypic pattern was classified as score 1, if all lesions were negative on both scans; score 2, if all were GaTATE positive/FDG negative; score 3, if all lesions were GaTATE positive but some or all were also FDG positive and score 4, if there were any GaTATE negative/FDG positive lesions. Scores 1 and 4 were deemed unsuitable for PRRT.

RESULTS

Of 56 patients (median age 66.5 years, 32 female), 22 had TC, and 34 had AC. Distant metastases were seen in 32% of TC and 94% of AC. At a median follow-up of 37 months for TC and 38 months for AC, 100% and 63% were alive, respectively. Median OS for AC was 56 months (95% CI 43, not reached [NR]), and TC was NR. On inter-patient dual-tracer analysis, scores 1, 2, 3 and 4 were 23%, 18%, 36% and 23% in TC and 3%, 15%, 32% and 50% in AC, respectively. In 16 patients (score 2, N = 3; score 3, N = 12; score 4, N = 1) who were treated with PRRT, disease control rate at 3 months and OS were, 85% and 54.6 months (95% CI 44-70), respectively.

CONCLUSIONS

TC and AC showed a wide inter-patient phenotypic heterogeneity on GaTATE and FDG with around half of patients (46% TC and 53% AC) having an unsuitable phenotype for PRRT. Dual-tracer MI phenotype can be used to select the most suitable patients for PRRT.

Peptide Receptor Radionuclide Therapy with 67Cu-CuSarTATE Is Highly Efficacious Against a Somatostatin-Positive Neuroendocrine Tumor Model

Peptide receptor radionuclide therapy (PRRT) using radiolabeled octreotate is an effective treatment for somatostatin receptor 2-expressing neuroendocrine tumors. The diagnostic and therapeutic potential of ⁶⁴Cu and ⁶⁷Cu, respectively, offers the possibility of using a single somatostatin receptor-targeted peptide conjugate as a theranostic agent. A sarcophagine cage amine ligand, MeCOSar (5-(8-methyl-3,6,10,13,16,19-hexaaza-bicyclo[6.6.6]icosan-1-ylamino)-5-oxopentanoic acid), conjugated to (Tyr³)-octreotate, called ⁶⁴Cu-CuSarTATE, was demonstrated to be an imaging agent and potential prospective dosimetry tool in 10 patients with neuroendocrine tumors. This study aimed to explore the antitumor efficacy of ⁶⁷Cu-CuSarTATE in a preclinical model of neuroendocrine tumors and compare it with the standard PRRT agent, ¹⁷⁷Lu-LuDOTA-Tyr³-octreotate (¹⁷⁷Lu-LuTATE). Methods: The antitumor efficacy of various doses of ⁶⁷Cu-CuSarTATE in AR42J (rat pancreatic exocrine) tumor-bearing mice was compared with ¹⁷⁷Lu-LuTATE. Results: Seven days after a single administration of ⁶⁷Cu-CuSarTATE (5 MBq), tumor growth was inhibited by 75% compared with vehicle control. Administration of ¹⁷⁷Lu-LuTATE (5 MBq) inhibited tumor growth by 89%. Survival was extended from 12 d in the control group to 21 d after treatment with both ⁶⁷Cu-CuSarTATE and ¹⁷⁷Lu-LuTATE. In a second study, the efficacy of fractionated delivery of PRRT was assessed, comparing the efficacy of 30 MBq of ⁶⁷Cu-CuSarTATE or ¹⁷⁷Lu-LuTATE, either as a single intravenous injection or as two 15-MBq fractions 2 wk apart. Treatment of tumors with 2 fractions significantly improved survival over delivery as a single fraction (⁶⁷Cu-CuSarTATE: 47 vs. 36 d [P = 0.036]; ¹⁷⁷Lu-LuTATE: 46 vs. 29 d [P = 0.040]). Conclusion: This study demonstrates that ⁶⁷Cu-CuSarTATE is well tolerated in BALB/c nude mice and highly efficacious against AR42J tumors in vivo. Administration of ⁶⁷Cu-CuSarTATE and ¹⁷⁷Lu-LuTATE divided into 2 fractions over 2 wk was more efficacious than administration of a single fraction. The antitumor activity of ⁶⁷Cu-CuSarTATE in the AR42J tumor model demonstrated the suitability of this novel agent for clinical assessment in the treatment of somatostatin receptor 2-expressing neuroendocrine tumors.

Evaluation of Pan-SSTRs Targeted Radioligand [64Cu]NOTA-PA1 Using Micro-PET Imaging in Xenografted Mice

⁶⁴Cu-labeled new pan-somatostatin receptors (pan-SSTRs) probe PA1 was synthesized, characterized, and evaluated by in vitro and in vivo experiments. [⁶⁴Cu]NOTA-PA1 was obtained with high specific activity, high radiochemical purity, and good stability. Cell uptake of [⁶⁴Cu]NOTA-PA1 was higher than that of [⁶⁴Cu]DOTA-TATE in MCF-7, A549, BGC823, and HT-29 cell lines. [⁶⁴Cu]NOTA-PA1 showed high binding affinity for SSTRs expressed in A549 cells. The in vivo biodistribution and micropositron emission tomography (micro-PET) imaging studies of [⁶⁴Cu]NOTA-PA1 revealed good detection ability in MCF-7 and A549 xenografted nude mice. The radiosynthesis, quality control, and preliminary biological evaluation of [⁶⁴Cu]NOTA-PA1 have broaden the application of radiolabeled octreotide for SSTRs imaging, which could act as a potential multisubtypes targeted radiotracer for imaging SSTRs-positive tumors.

Favorable Outcome in Patients with Pheochromocytoma and Paraganglioma Treated with 177Lu-DOTATATE

Peptide receptor radiotherapy (PRRT) with ¹⁷⁷Lu-DOTATATE has emerged as a promising therapy for neuroendocrine tumors (NETs). This retrospective cohort study aimed to assess the outcome of PRRT for 22 patients with histopathologically confirmed pheochromocytoma (PCC) and paraganglioma (PGL), of which two were localized and 20 metastatic. Radiological response utilized response evaluation criteria in solid tumors 1.1 and toxicity was graded according to common terminology criteria for adverse events version 4. Median 4 (range 3–11) 7.4 GBq cycles of ¹⁷⁷Lu-DOTATATE were administered as first-line therapy (n = 13) or because of progressive disease (n = 9). Partial response (PR) was achieved in two and stable disease (SD) in 20 patients. The median overall survival (OS) was 49.6 (range 8.2–139) months and median progression-free survival (PFS) was 21.6 (range 6.7–138) months. Scintigraphic response >50% was achieved in 9/19 (47%) patients. Biochemical response (>50% decrease) of chromogranin A was found in 6/15 (40%) patients and of catecholamines in 3/12 (25%) patients. Subgroup analysis showed Ki-67 <15% associated with longer OS (p = 0.013) and PFS (p = 0.005). PRRT as first-line therapy was associated with increased OS (p = 0.041). No hematological or kidney toxicity grade 3–4 was registered. ¹⁷⁷Lu-DOTATATE therapy was associated with favorable outcome and low toxicity. High Ki-67 (≥15%) and PRRT received because of progression on previous therapy could constitute negative predictive factors for OS.