Safety and outcomes of 177 Lu-DOTATATE for neuroendocrine tumours: experience in New South Wales, Australia

SPECT/CT Image-Derived Absorbed Dose to Red Marrow Correlates with Hematologic Toxicity in Patients Treated with [177Lu]Lu-DOTATATE

Hematologic toxicity, although often transient, is the most common limiting adverse effect during somatostatin peptide receptor radionuclide therapy. This study investigated the association between Monte Carlo-derived absorbed dose to the red marrow (RM) and hematologic toxicity in patients being treated for their neuroendocrine tumors. Methods: Twenty patients each receiving 4 treatment cycles of [177Lu]Lu-DOTATATE were included. Multiple-time-point 177Lu SPECT/CT imaging-based RM dosimetry was performed using an artificial intelligence-driven workflow to segment vertebral spongiosa within the field of view (FOV). This workflow was coupled with an in-house macroscale/microscale Monte Carlo code that incorporates a spongiosa microstructure model. Absorbed dose estimates to RM in lumbar and thoracic vertebrae within the FOV, considered as representations of the whole-body RM absorbed dose, were correlated with hematologic toxicity markers at about 8 wk after each cycle and at 3- and 6-mo follow-up after completion of all cycles. Results: The median of absorbed dose to RM in lumbar and thoracic vertebrae within the FOV (D median,vertebrae) ranged from 0.019 to 0.11 Gy/GBq. The median of cumulative absorbed dose across all 4 cycles was 1.3 Gy (range, 0.6-2.5 Gy). Hematologic toxicity was generally mild, with no grade 2 or higher toxicity for platelets, neutrophils, or hemoglobin. However, there was a decline in blood counts over time, with a fractional value relative to baseline at 6 mo of 74%, 97%, 57%, and 97%, for platelets, neutrophils, lymphocytes, and hemoglobin, respectively. Statistically significant correlations were found between a subset of hematologic toxicity markers and RM absorbed doses, both during treatment and at 3- and 6-mo follow-up. This included a correlation between the platelet count relative to baseline at 6-mo follow up: D median,vertebrae (r = -0.64, P = 0.015), D median,lumbar (r = -0.72, P = 0.0038), D median,thoracic (r = -0.58, P = 0.029), and D average,vertebrae (r = -0.66, P = 0.010), where D median,lumbar and D median,thoracic are median absorbed dose to the RM in the lumbar and thoracic vertebrae, respectively, within the FOV and D average,vertebrae is the mass-weighted average absorbed dose of all vertebrae. Conclusion: This study found a significant correlation between image-derived absorbed dose to the RM and hematologic toxicity, including a relative reduction of platelets at 6-mo follow up. These findings indicate that absorbed dose to the RM can potentially be used to understand and manage hematologic toxicity in peptide receptor radionuclide therapy.

Specific Uptake in the Bone Marrow Causes High Absorbed Red Marrow Doses During [177Lu]Lu-DOTATATE Treatment

Bone marrow suppression is a common side effect after [177Lu]Lu-DOTATATE treatment of neuroendocrine neoplasms. Neuroendocrine neoplasms share expression of somatostatin receptor type 2 with CD34-positive hematopoietic progenitor cells, potentially leading to active uptake in the radiosensitive red marrow region where these cells are located. This study aimed to identify and quantify specific red marrow uptake using SPECT/CT images collected after the first treatment cycle. Methods: Seventeen patients diagnosed with neuroendocrine neoplasms were treated with [177Lu]Lu-DOTATATE. Seven of them had confirmed bone metastases. After the first treatment cycle, each patient went through 4 SPECT/CT imaging sessions 4, 24, 48, and 168 h after administration. Monte Carlo-based reconstructions were used to quantify activity concentrations in tumors and multiple skeletal sites presumed to house red marrow: the T9-L5 vertebrae and the ilium portion of the hip bones. The activity concentration from the descending aorta was used as input in a compartment model intended to establish a pure red marrow biodistribution by separating the nonspecific blood-based contribution from the specific activity concentration in red marrow. The biodistributions from the compartment model were used to perform red marrow dosimetry at each skeletal site. Results: Increased uptake of [177Lu]Lu-DOTATATE was observed in the T9-L5 vertebrae and hip bones in all 17 patients compared with activity concentrations in the aorta. The mean specific red marrow uptake was 49% (range, 0%-93%) higher than the nonspecific uptake. The median (±SD) total absorbed dose to the red marrow was 0.056 ± 0.023 Gy/GBq and 0.043 ± 0.022 Gy/GBq for the mean of all vertebrae and hip bones, respectively. The patients with bone metastases had an absorbed dose of 0.085 ± 0.046 Gy/GBq and 0.069 ± 0.033 Gy/GBq for the vertebrae and hip bones, respectively. The red marrow elimination phase was statistically slower in patients with fast tumor elimination, which is in line with transferrin transport of 177Lu back to the red marrow. Conclusion: Our results suggest that specific red marrow uptake of [177Lu]Lu-DOTATATE is in line with observations of somatostatin receptor type 2-expressing hematopoietic progenitor cells within the bone marrow. Blood-based dosimetry methods fail to account for the prolonged elimination of specific uptake and underestimate the absorbed dose to red marrow.

Single-centre experience with peptide receptor radionuclide therapy for neuroendocrine tumours (NETs): results using a theranostic molecular imaging-guided approach

AIM

To summarise our centre's experience managing patients with neuroendocrine tumours (NETs) in the first 5 years after the introduction of peptide receptor radionuclide therapy (PRRT) with [177Lu]Lu-DOTA-octreotate (LUTATE). The report emphasises aspects of the patient management related to functional imaging and use of radionuclide therapy.

METHODS

We describe the criteria for treatment with LUTATE at our centre, the methodology for patient selection, and the results of an audit of clinical measures, imaging results and patient-reported outcomes. Subjects are treated initially with four cycles of ~ 8 GBq of LUTATE administered as an outpatient every 8 weeks.

RESULTS

In the first 5 years offering LUTATE, we treated 143 individuals with a variety of NETs of which approx. 70% were gastroentero-pancreatic in origin (small bowel: 42%, pancreas: 28%). Males and females were equally represented. Mean age at first treatment with LUTATE was 61 ± 13 years with range 28-87 years. The radiation dose to the organs considered most at risk, the kidneys, averaged 10.6 ± 4.0 Gy in total. Median overall survival (OS) from first receiving LUTATE was 72.5 months with a median progression-free survival (PFS) of 32.3 months. No evidence of renal toxicity was seen. The major long-term complication seen was myelodysplastic syndrome (MDS) with a 5% incidence.

CONCLUSIONS

LUTATE treatment for NETs is a safe and effective treatment. Our approach relies heavily on functional and morphological imaging informing the multidisciplinary team of NET specialists to guide appropriate therapy, which we suggest has contributed to the favourable outcomes seen.

Long-Term Outcomes of Submaximal Activities of Peptide Receptor Radionuclide Therapy with 177Lu-DOTATATE in Neuroendocrine Tumor Patients

In the literature, up to 45% of neuroendocrine tumor (NET) patients who are treated with ¹⁷⁷Lu-DOTATATE peptide receptor radionuclide therapy (PRRT) do not receive the intended cumulative activity of 29.6 GBq (800 mCi). The aim of this study was to analyze the efficacy of submaximal activities of PRRT in patients who discontinued treatment for non-disease-related reasons. Methods: We retrospectively included patients with well-differentiated and advanced NETs who underwent PRRT from 2000 until 2019 and did not receive 29.6 GBq of ¹⁷⁷Lu-DOTATATE. For comparison, we selected control NET patients who received the intended cumulative activity of 29.6 GBq of ¹⁷⁷Lu-DOTATATE between 2000 and 2012. Primary outcomes were progression-free survival (PFS) and tumor response, and the secondary outcome was overall survival (OS). Results: In total, 243 patients received 3.7-27.8 GBq. In 130 patients, the submaximal activity was unrelated to disease (e.g., bone marrow and renal toxicity in 48% and maximal renal absorbed dose in 23%), and they were included. Patients receiving a reduced activity had more bone metastases, a lower body mass index and albumin level, a higher alkaline phosphatase level, and fewer grade 1 tumors than the 350 patients included in the control group. The disease control rate in the reduced-activity group was 85%, compared with 93% for the control group (P = 0.011). The median PFS (95% CI) was 23 mo (range, 21-26 mo) for the reduced-activity group and 31 mo (range, 27-35 mo) for the control group (P = 0.001), and the median OS (95% CI) was 34 mo (range, 28-40 mo) and 60 mo (range, 53-67 mo), respectively (P < 0.0001). With adjustment for relevant confounders in the multivariable Cox regression analyses, cumulative activity was an independent predictor of both PFS and OS. Conclusion: In NET patients treated with a cumulative activity of less than 29.6 GBq of ¹⁷⁷Lu-DOTATATE, PRRT was less efficacious in tumor response and survival than in patients who received 29.6 GBq.

A Clinical Guide to Peptide Receptor Radionuclide Therapy with 177Lu-DOTATATE in Neuroendocrine Tumor Patients

Peptide receptor radionuclide therapy (PRRT) with [¹⁷⁷Lu]Lu-[DOTA⁰,Tyr³]-octreotate (¹⁷⁷Lu-DOTATATE) has become an established second- or third-line treatment option for patients with somatostatin receptor (SSTR)-positive advanced well-differentiated gastroenteropancreatic (GEP) neuroendocrine tumors (NETs). Clinical evidence of the efficacy of PRRT in tumor control has been proven and lower risks of disease progression or death are seen combined with an improved quality of life. When appropriate patient selection is performed, PRRT is accompanied by limited risks for renal and hematological toxicities. Treatment of NET patients with PRRT requires dedicated clinical expertise due to the biological characteristics of PRRT and specific characteristics of NET patients. This review provides an overview for clinicians dealing with NET on the history, molecular characteristics, efficacy, toxicity and relevant clinical specifics of PRRT.

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.

Quantitative SPECT/CT for dosimetry of peptide receptor radionuclide therapy

Neuroendocrine tumors (NETs) are uncommon malignancies of increasing incidence and prevalence. As these slow growing tumors usually overexpress somatostatin receptors (SSTRs), the use of ⁶⁸Ga-DOTA-peptides (gallium-68 chelated with dodecane tetra-acetic acid to somatostatin), which bind to the SSTRs, allows for PET based imaging and selection of patients for peptide receptor radionuclide therapy (PRRT). PRRT with radiolabeled somatostatin analogues such as ¹⁷⁷Lu-DOTATATE (lutetium-177-[DOTA,Tyr³]-octreotate), is mainly used for the treatment of metastatic or inoperable NETs. However, PRRT is generally administered at a fixed injected activity in order not to exceed dose limits in critical organs, which is suboptimal given the variability in radiopharmaceutical uptake among patients. Advances in SPECT (single photon emission computed tomography) imaging enable the absolute quantitative measure of the true radiopharmaceutical distribution providing for PRRT dosimetry in each patient. Personalized PRRT based on patient-specific dosimetry could improve therapeutic efficacy by optimizing effective tumor absorbed dose while limiting treatment related radiotoxicity.

Quantitative 68Ga-DOTATATE PET/CT Parameters for the Prediction of Therapy Response in Patients with Progressive Metastatic Neuroendocrine Tumors Treated with 177Lu-DOTATATE

The aim of this study was to determine whether quantitative PET parameters on baseline 68Ga-DOTATATE PET/CT and interim PET (iPET) performed before the second cycle of therapy are predictive of the therapy response and progression-free survival (PFS). Methods: Ninety-one patients with well-differentiated neuroendocrine tumors (mean Ki-67 index, 8.3%) underwent 68Ga-DOTATATE PET/CT to determine suitability for peptide receptor radionuclide therapy as part of a prospective multicenter study. The mean follow-up was 12.2 mo. Of the 91 patients, 36 had iPET. The tumor metrics evaluated were marker lesion-based measures (mean SUVmax and ratio of the mean lesion SUVmax to the SUVmax in the liver or the SUVmax in the spleen), segmented 68Ga-DOTATATE tumor volumes (DTTVs), SUVmax and SUVmean obtained with the liver and spleen as thresholds, and heterogeneity parameters (coefficient of variation, kurtosis, and skewness). The Wilcoxon rank sum test was used for the association between continuous variables and the therapy response, as determined by the clinical response. Univariable and multivariable Cox proportional hazards models were used for the association with PFS. Results: There were 71 responders and 20 nonresponders. When marker lesions were used, higher mean SUVmax and ratio of the mean lesion SUVmax to the SUVmax in the liver were predictors of the therapy response (P = 0.018 and 0.024, respectively). For DTTV parameters, higher SUVmax and SUVmean obtained with the liver as a threshold and lower kurtosis were predictors of a favorable response (P = 0.025, 0.0055, and 0.031, respectively). The latter also correlated with a longer PFS. The iPET DTTV SUVmean obtained with the liver as a threshold and the ratio of mean SUVmax obtained from target lesions at iPET to baseline PET correlated with the therapy response (P = 0.024 and 0.048, respectively) but not PFS. From the multivariable analysis with adjustment for age, primary site, and Ki-67 index, the mean SUVmax (P = 0.019), ratio of the mean lesion SUVmax to the SUVmax in the liver (P = 0.018), ratio of the mean lesion SUVmax to the SUVmax in the spleen (P = 0.041), DTTV SUVmean obtained with the liver (P = 0.0052), and skewness (P = 0.048) remained significant predictors of PFS. Conclusion: The degree of somatostatin receptor expression and tumor heterogeneity, as represented by several metrics in our analysis, were predictive of the therapy response or PFS. Changes in these parameters after the first cycle of peptide receptor radionuclide therapy did not correlate with clinical outcomes.

Neuroendocrine Tumors: Imaging Perspective

This article summarizes the role of PET imaging for detection, characterization, and theranostic/therapy planning for neuroendocrine tumors. Topics in this article span overall imaging accuracy with mostly ⁶⁸Ga-DOTA-peptide imaging as well as basic principles of individualized dosimetry. There is also some discussion around further specialized approaches in dosimetry in theranostics. In addition, an overview of the literature on functional imaging in neuroendocrine tumors and the current understanding of imaging-derived clinical outcome prediction are presented.

Laboratory, Clinical, and Survival Outcomes Associated With Peptide Receptor Radionuclide Therapy in Patients With Gastroenteropancreatic Neuroendocrine Tumors

IMPORTANCE

Peptide receptor radionuclide therapy (PRRT) is approved in the US for treatment of gastroenteropancreatic neuroendocrine tumors (NETs), but data on PRRT outcomes within US populations remain scarce.

OBJECTIVE

To analyze the first 2 years of PRRT implementation at a US-based NET referral center.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study was conducted using medical records of patients with metastatic NET receiving PRRT from 2018 through 2020 in a NET program at a tertiary referral center. Included patients were those at the center with metastatic NETs who received at least 1 dose of PRRT over the study period. Laboratory toxic effects were assessed using Common Terminology Criteria for Adverse Events version 5.0. Tumor response was determined using Response Evaluation Criteria in Solid Tumors 1.1. Survival analysis was conducted to identify factors associated with progression-free survival (PFS) and overall survival. Data were analyzed from August 2018 through August 2020.

EXPOSURES

Receiving 4 cycles of lutetium-177-dotatate infusion, separated by 8-week intervals targeted to 7.4 GBq (200 mCi) per dose.

MAIN OUTCOMES AND MEASURES

Data were compared from before and after PRRT to determine hematologic, liver, and kidney toxic effects and to assess tumor progression and patient survival.

RESULTS

Among 78 patients receiving at least 1 dose of PRRT, median (interquartile range) age at PRRT initiation was 59.8 (53.5-69.2) years and 39 (50.0%) were men. The most common primary NET sites included small bowel, occurring in 34 patients (43.6%), and pancreas, occurring in 22 patients (28.2%). World Health Organization grade 1 or 2 tumors occurred in 62 patients (79.5%). Among all patients, 56 patients underwent pretreatment with tumor resection (71.8%), 49 patients received nonsomatostatin analogue systemic therapy (62.8%), and 49 patients received liver-directed therapy (62.8%). At least 1 grade 2 or greater toxic effect was found in 47 patients (60.3%). Median PFS was 21.6 months for the study group, was not reached by 22 months for patients with small bowel primary tumors, and was 13.3 months for patients with pancreatic primary tumors. Having a small bowel primary tumor was associated with a lower rate of progression compared with having a pancreatic primary tumor (hazard ratio, 0.19; 95% CI, 0.07-0.55; P = .01). Median overall survival was not reached.

CONCLUSIONS AND RELEVANCE

This cohort study of patients with metastatic NETs found that PRRT was associated with laboratory-measured toxic effects during treatment for most patients and an overall median PFS of 21.6 months. Patients with small bowel NETs had longer PFS after PRRT compared with patients with pancreatic NETs.

Therapy-related chronic myeloid leukemia in a patient receiving peptide receptor radionuclide therapy for pancreatic neuroendocrine tumor

BACKGROUND

Therapy-related leukemia is a well-recognized clinical syndrome. Peptide receptor radionuclide therapy (PRRT) is a modern therapeutic approach using radionuclide combined with somatostatin analog peptide for inoperable or metastatic neuroendocrine tumors.

AIMS

Hematologic toxicities including late-onset myeloid neoplasms have been reported after PRRT; however, therapy-related chronic myeloid leukemia (TR-CML) following PRRT is a relatively rare entity.

METHODS

We present a 64-year-old male who received PRRT for pancreas neuroendocrine tumor and then developed TR-CML 60 months after the initiation of PRRT. The patient responded well to imatinib therapy.

RESULTS

Patients with TR-CML generally have similar tyrosine kinase inhibitor responses and outcomes when compared to de novo cases.

CONCLUSIONS

The physicians should be aware of the short- and long-term hematologic toxicities of PRRT including TR-CML, and careful monitoring is mandatory in this group of patients.

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.

Multidisciplinary Management of Neuroendocrine Neoplasia: A Real-World Experience from a Referral Center

PURPOSE

Multidisciplinary approach is widely advised for an effective care of patients with neuroendocrine neoplasia (NEN). Since data on efficacy of multidisciplinary management of NENs patients in referral centers are scanty, this study aimed at analyzing the modality of presentation and clinical outcome of patients with NENs managed by a dedicated multidisciplinary team.

METHODS

In this prospective observational study, we included all consecutive new patients visiting the Sant'Andrea Hospital in Rome (ENETS-Center of Excellence) between January 2014 and June 2018.

RESULTS

A total of 195 patients were evaluated. The most frequent sites were pancreas (38.5%), small bowel (22%), and lung (9.7%). Median Ki67 was 3%. After the first visit at the center, additional radiological and/or nuclear medicine procedures were requested in 163 patients (83.6%), whereas histological data revision was advised in 84 patients (43.1%) (revision of histological slides: 27.7%, new bioptic sampling: 15.4%). After that, disease imaging staging and grading was modified in 30.7% and 17.9% of patients, respectively. Overall, a change in therapeutic management was proposed in 98 patients (50.3%).

CONCLUSIONS

Multidisciplinary approach in a dedicated team may lead to change of disease imaging staging and grading in a significant proportion of patients. Enhancing referral routes to dedicated-NEN center should be promoted, since it may improve patients' clinical outcome.