Long-Term Hematotoxicity After Peptide Receptor Radionuclide Therapy with 177Lu-Octreotate

Safety and Efficacy of 177 Lu-DOTATATE in Children and Young Adult Population : A Single-Center Experience

PURPOSE

This single-center retrospective study explores the safety and efficacy of 177 Lu-DOTATATE in children and young adult population with metastatic/inoperable neuroendocrine tumors (NETs).

PATIENTS AND METHODS

This study is a retrospective analysis of all children and young adult patients (≤29 years) with advanced inoperable/metastatic epithelial or nonepithelial NETs who were administered a median of 4 cycles of 177 Lu-DOTATATE therapy and low-dose oral capecitabine as a radiosensitizer every 8-12 weeks, except 2 patients who received CAPTEM chemotherapy. The radiological response was assessed using RECIST 1.1 on interim and end-of-treatment 68 Ga-DOTANOC PET/CT. The primary endpoint was objective response rate, whereas disease control rate, toxicity profile, progression-free survival, and overall survival were secondary endpoints.

RESULTS

Nineteen biopsy-proven NET patients (median age, 22 ± 10 years) with 8 of them adolescents (10-18 years) and the remaining young adults (19-29 years) were included. Fourteen patients had gastroenteropancreatic neuroendocrine tumor (pancreas being most common primary site), whereas the rest had non-gastroenteropancreatic neuroendocrine tumor. A total of 65 cycles of 177 Lu-DOTATATE (range, 1-6 cycles) were administered with a median cumulative activity of 600 mCi (range, 100-1000 mCi). The objective response rate and disease control rate were 41% and 94%, respectively. Grade 1 and 2 adverse events were observed in 14 (74%) and 5 (26%) of 19 patients, respectively. In a total of 8 events (42%), 4 events each of disease progression and death occurred during a median follow-up of 80.1 months with an estimated 5-year progression-free survival and overall survival of 54% (95% confidence interval, 30-78) and 63% (95% confidence interval, 39-87), respectively.

CONCLUSIONS

177 Lu-DOTATATE appears safe and effective in children and young adults with metastatic/inoperable NETs. Large prospective trials are required to validate these results.

177Lu-DOTATATE PRRT Safety and Organ-at-Risk Dosimetry in Patients With Gastroenteropancreatic Neuroendocrine Tumors: Data From the Prospective Phase 2 LUMEN Study

PURPOSE

The aim of this study was to assess the association among toxicity, dosimetry of organs-at-risk, and disease progression in patients with gastroenteropancreatic neuroendocrine tumors (GEP-NETs) treated with 177Lu-DOTATATE.

PATIENTS AND METHODS

Thirty-seven patients with GEP-NETs underwent 177Lu-DOTATATE peptide receptor radionuclide therapy (PRRT) in a single-arm, prospective, phase 2 study, where patients were followed up with blood tests, isotopic glomerular filtration rate (iGFR), and imaging examinations (CT/MRI and PET) every 6 months until disease progression. Adverse events (AEs) graded per CTCAEv4.03 and occurring during treatment were collected and followed up until resolution. Dosimetry, including biologically effective doses (BEDs) to kidneys, BED to bone marrow, and absorbed dose (AD) to spleen, was performed after each PRRT cycle. Statistical analyses explored associations among dosimetry, toxicity, and patient progression free-survival.

RESULTS

The most common AEs were anemia and lymphopenia (65%), followed by thrombocytopenia and fatigue (each 51%), alopecia (46%), and nausea (41%). The most common grade ≥3 AE was lymphopenia (43%). There was no grade ≥3 nephrotoxicity. The median iGFR % decrease was 11% (P < 0.001), at a median follow-up of 23 months. iGFR %decrease and renal BED did not correlate (Spearman ρ = -0.09). Similarly, no significant association was found between bone marrow BED or spleen AD and the grades of hematological toxicities. We observed no association between progression free-survival and either the decline of renal function or the occurrence of hematological toxicities during PRRT.

CONCLUSIONS

This study confirms the safety profile of 177Lu-DOTATATE PRRT in patients with GEP-NETs irrespective of the dosimetry of organs at risk. Kidney, bone marrow, and spleen dosimetry measures were not associated with renal or hematological toxicity.

Safety and Efficacy of Para-Aminohippurate Coinfusion for Renal Protection During Peptide Receptor Radiotherapy in Patients with Neuroendocrine Tumors

Para-aminohippurate, also known as p-aminohippuric acid (PAH), is used clinically to measure effective renal plasma flow. Preclinically, it was shown to reduce 177Lu-DOTATOC uptake in the kidneys while improving bioavailability compared with amino acid (AA) coinfusion. We report the safety and efficacy of PAH coinfusion during peptide receptor radiotherapy in patients with neuroendocrine tumors. Methods: Twelve patients with metastatic or unresectable gastroenteropancreatic neuroendocrine tumors received 177Lu-DOTATOC in 33 treatment cycles. Either 8 g of PAH or a mixture of 25 g of arginine and 25 g of lysine were coinfused. Safety was assessed by monitoring laboratory data, including hematologic and renal data, as well as electrolytes obtained before and 24 h after treatment. For radiation dosimetry, whole-body scans were performed at 1, 24, and 48 h and a SPECT/CT scan was performed at 48 h, along with blood sampling at 5 min and 0.5, 2, 4, 24, and 48 h after administration. Absorbed dose estimations for the kidneys and bone marrow were performed according to the MIRD concept. Results: In 15 treatment cycles, PAH was coinfused. No changes in mean creatinine level, glomerular filtration rate, and serum electrolytes were observed before or 24 h after treatment when using PAH protection (P ≥ 0.20), whereas serum chloride and serum phosphate increased significantly under AA (both P < 0.01). Kidney-absorbed dose coefficients were 0.60 ± 0.14 Gy/GBq with PAH and 0.53 ± 0.16 Gy/GBq with AA. Based on extrapolated cumulative kidney-absorbed doses for 4 cycles, 1 patient with PAH protection and 1 patient with AA protection in our patient group would exceed the 23-Gy conservative threshold. The bone marrow-absorbed dose coefficient was 0.012 ± 0.004 Gy/GBq with PAH and 0.012 ± 0.003 Gy/GBq with AA. Conclusion: PAH is a promising alternative to AA for renal protection during peptide receptor radiotherapy. Further research is required to systematically investigate the safety profile and radiation dosimetry at varying PAH plasma concentrations.

Repeat Peptide Receptor Radionuclide Therapy in Neuroendocrine Tumors: A NET Center of Excellence Experience

INTRODUCTION

The available data for the safety and efficacy of repeat peptide receptor radionuclide therapy (PRRT) are almost exclusively from European centers. We present an updated experience with repeat PRRT in a cohort of US patients with neuroendocrine tumors (NETs) at our NET center of excellence.

METHODS

We used our single-center longitudinal NET registry to identify patients who had been previously treated with at least one dose of PRRT (PRRT 1, either 177Lu DOTATATE or 90Y DOTATOC) and following radiographic disease progression were re-treated with a second course of PRRT (PRRT 2). We reviewed patient, tumor and treatment characteristics, objective response rates, and toxicities after PRRT 1 and PRRT 2.

RESULTS

A total of 11 patients were included in the analysis. 45.5% (5/11) of patients received 177Lu DOTATATE PRRT only, both for PRRT1 and PRRT 2, while 54.5% (6/11) of patients received 90Y DOTATOC PRRT for PRRT1. At first restaging scan after PRRT2 (3-6 months), 18.2% (2/11), 36.4% (4/11), and 27.3% (3/11) of patients had PR, SD, and PD, respectively; 2/11 patients (18.2%) died before the first restaging scan. Therefore, 5/11 (45.5%) patients were noted to have disease progression. Median PFS for PRRT1 was 25.4 months and median PFS for PRRT2 was 13.1 months (p = 0.0001). We did not find a statistically significant difference between the occurrence of short and long-term hematological toxicities as well as renal toxicity after PRRT1 and PRRT2.

CONCLUSION

We show that repeat PRRT may benefit select patients and have an acceptable safety profile. In our cohort, PFS was significantly lower after PRRT2 as compared to PRRT1.

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.

Impact of different models based on blood samples and images for bone marrow dosimetry after 177Lu-labeled somatostatin-receptor therapy

BACKGROUND

Peptide receptor radionuclide therapy with 177Lu-DOTATATE is a recognized option for treating neuroendocrine tumors and has few toxicities, except for the kidneys and bone marrow. The bone marrow dose is generally derived from a SPECT/CT image-based method with four timepoints or from a blood-based method with up to 9 timepoints, but there is still no reference method. This retrospective single-center study on the same cohort of patients compared the calculated bone marrow dose administered with both methods using mono, bi- or tri-exponential models. For the image-based method, the dose was estimated using Planetdose© software. Pearson correlation coefficients were calculated. We also studied the impact of late timepoints for both methods.

RESULTS

The bone marrow dose was calculated for 131 treatments with the blood-based method and for 17 with the image-based method. In the former, the median absorbed dose was 15.3, 20.5 and 28.3 mGy/GBq with the mono-, bi- and tri-exponential model, respectively. With the image-based method, the median absorbed dose was 63.9, 41.9 and 60.8 with the mono-, bi- and tri-exponential model, respectively. Blood samples after 24h post-injection did not evidence any change in the absorbed bone marrow dose with the bi-exponential model. On the contrary, the 6-day post-injection timepoint was more informative with the image-based model.

CONCLUSION

This study confirms that the estimated bone marrow dose is significantly lower with the blood-based method than with the image-based method. The blood-based method with a bi-exponential model proved particularly useful, without the need for blood samples after 24h post-injection. Nevertheless, this blood-based method is based on an assumption that needs to be more validated. The important difference between the two methods does not allow to determine the optimal one to estimate the true absorbed dose and further studies are necessary to compare with biological effects.

A single-institution experience with 177Lu RPT workflow improvements and qualifying the SPECT/CT imaging for dosimetry

Background and purpose

Implementing any radiopharmaceutical therapy (RPT) program requires a comprehensive review of system readiness, appropriate workflows, and training to ensure safe and efficient treatment delivery. A quantitative assessment of the dose delivered to targets and organs at risk (OAR) using RPT is possible by correlating the absorbed doses with the delivered radioactivity. Integrating dosimetry into an established RPT program demands a thorough analysis of the necessary components and system fine-tuning. This study aims to report an optimized workflow for molecular radiation therapy using 177Lu with a primary focus on integrating patient-specific dosimetry into an established radiopharmaceutical program in a radiation oncology setting.

Materials and methods

We comprehensively reviewed using the Plan-Do-Check-Act (PDCA) cycle, including efficacy and accuracy of delivery and all aspects of radiation safety of the RPT program. The GE Discovery SPECT/CT 670DR™ system was calibrated per MIM protocol for dose calculation on MIM SurePlan™ MRT software. Jaszcak Phantom with 15-20 mCi of 177Lu DOTATATE with 2.5 µM EDTA solution was used, with the main energy window defined as 208 keV ±10% (187.6 to 229.2 keV); the upper scatter energy window was set to 240 keV ±5% (228 to 252 keV), while the lower scatter energy window was 177.8 keV ±5% (168.9 to 186.7 keV). Volumetric quality control tests and adjustments were performed to ensure the correct alignment of the table, NM, and CT gantry on SPECT/CT. A comprehensive end-to-end (E2E) test was performed to ensure workflow, functionality, and quantitative dose accuracy.

Results

Workflow improvements and checklists are presented after systematically analyzing over 400 administrations of 177Lu-based RPT. Injected activity to each sphere in the NEMA Phantom scan was quantified, and the MIM Sureplan MRT reconstruction images calculated activities within ±12% of the injected activity. Image alignment tests on the SPECT/CT showed a discrepancy of more than the maximum tolerance of 2.2 mm on any individual axis. As a result of servicing the machine and updating the VQC and COR corrections, the hybrid imaging system was adjusted to achieve an accuracy of <1 mm in all directions.

Conclusion

Workflows and checklists, after analysis of system readiness and adequate training for staff and patients, are presented. Hardware and software components for patient-specific dosimetry are presented with a focus on hybrid image registration and correcting any errors that affect dosimetric quantification calculation. Moreover, this manuscript briefly overviews the necessary quality assurance requirements for converting diagnostic images into dosimetry measurement tools and integrating dosimetry for RPT based on 177Lu.

Risk of treatment-altering haematological toxicity and its dependence on bone marrow doses in peptide receptor radionuclide therapy

BACKGROUND

Peptide receptor radionuclide therapy is effective in treating neuroendocrine tumours, but treatment may be limited by kidney and bone marrow toxicity. In this work, the absorbed dose burden to the bone marrow was estimated using image-based dosimetry and its potential use for predicting treatment-altering toxicity was studied. Peripheral blood samples taken before and after 229 treatments with 177Lu-DOTATATE in 59 patients were studied. In connection to the treatments, a total of 940 blood sample occasions provided data on white blood cell, neutrophil granulocyte, platelet, erythrocyte and haemoglobin concentrations. SPECT/CT image data were collected at two or three time points after each treatment. Absorbed doses to bone marrow were calculated from the activity concentration in a metastasis-free lumbar vertebra. The rate of delayed and aborted treatments was analysed based on medical records.

RESULTS

The average absorbed dose to the bone marrow was 0.42 Gy (median 0.33 Gy, SD 0.27 Gy) per treatment. Dose-response relationships between white blood cells, neutrophil granulocytes and haemoglobin concentrations were observed, most prominently at 31-45 days after each treatment. The correlations were stronger in patients with skeletal metastases. The rates of haematological toxicity-related delays and aborted treatments were 6% and 12%, respectively. None of the studied bone marrow dosimetric parameters could clearly predict treatment-related toxicity. However, patients with skeletal metastases had higher risk of treatment-altering toxicity (odds ratio = 6.0).

CONCLUSIONS

Treatment-altering haematological toxicity in peptide receptor radionuclide therapy is relatively rare and appears difficult to fully predict from post-therapeutic image-based dosimetry. However, for patients with skeletal metastases, the haematological dose-response relationships are stronger. Future studies may focus on this patient group, to further investigate the usefulness of dosimetry in predicting decreases in blood values.

A radiomic- and dosiomic-based machine learning regression model for pretreatment planning in 177 Lu-DOTATATE therapy

BACKGROUND

Standardized patient-specific pretreatment dosimetry planning is mandatory in the modern era of nuclear molecular radiotherapy, which may eventually lead to improvements in the final therapeutic outcome. Only a comprehensive definition of a dosage therapeutic window encompassing the range of absorbed doses, that is, helpful without being detrimental can lead to therapy individualization and improved outcomes. As a result, setting absorbed dose safety limits for organs at risk (OARs) requires knowledge of the absorbed dose-effect relationship. Data sets of consistent and reliable inter-center dosimetry findings are required to characterize this relationship.

PURPOSE

We developed and standardized a new pretreatment planning model consisting of a predictive dosimetry procedure for OARs in patients with neuroendocrine tumors (NETs) treated with 177 Lu-DOTATATE (Lutathera). In the retrospective study described herein, we used machine learning (ML) regression algorithms to predict absorbed doses in OARs by exploiting a combination of radiomic and dosiomic features extracted from patients' imaging data.

METHODS

Pretreatment and posttreatment data for 20 patients with NETs treated with 177 Lu-DOTATATE were collected from two clinical centers. A total of 3412 radiomic and dosiomic features were extracted from the patients' computed tomography (CT) scans and dose maps, respectively. All dose maps were generated using Monte Carlo simulations. An ML regression model was designed based on ML algorithms for predicting the absorbed dose in every OAR (liver, left kidney, right kidney, and spleen) before and after the therapy and between each therapy session, thus predicting any possible radiotoxic effects.

RESULTS

We evaluated nine ML regression algorithms. Our predictive model achieved a mean absolute dose error (MAE, in Gy) of 0.61 for the liver, 1.58 for the spleen, 1.30 for the left kidney, and 1.35 for the right kidney between pretherapy 68 Ga-DOTATOC positron emission tomography (PET)/CT and posttherapy 177 Lu-DOTATATE single photon emission (SPECT)/CT scans. Τhe best predictive performance observed was based on the gradient boost for the liver, the left kidney and the right kidney, and on the extra tree regressor for the spleen. Evaluation of the model's performance according to its ability to predict the absorbed dose in each OAR in every possible combination of pretherapy 68 Ga-DOTATOC PET/CT and any posttherapy 177 Lu-DOTATATE treatment cycle SPECT/CT scans as well as any 177 Lu-DOTATATE SPECT/CT treatment cycle and the consequent 177 Lu-DOTATATE SPECT/CT treatment cycle revealed mean absorbed dose differences ranges from -0.55 to 0.68 Gy. Incorporating radiodosiomics features from the 68 Ga-DOTATOC PET/CT and first 177 Lu-DOTATATE SPECT/CT treatment cycle scans further improved the precision and minimized the standard deviation of the predictions in nine out of 12 instances. An average improvement of 57.34% was observed (range: 17.53%-96.12%). However, it's important to note that in three instances (i.e., Ga,C.1 → C3 in spleen and left kidney, and Ga,C.1 → C2 in right kidney) we did not observe an improvement (absolute differences of 0.17, 0.08, and 0.05 Gy, respectively). Wavelet-based features proved to have high correlated predictive value, whereas non-linear-based ML regression algorithms proved to be more capable than the linear-based of producing precise prediction in our case.

CONCLUSIONS

The combination of radiomics and dosiomics has potential utility for personalized molecular radiotherapy (PMR) response evaluation and OAR dose prediction. These radiodosiomic features can potentially provide information on any possible disease recurrence and may be highly useful in clinical decision-making, especially regarding dose escalation issues.

Efficacy, Toxicity, and Prognostic Factors of Re-treatment With [177Lu]Lu-DOTA-TATE in Patients With Progressing Neuroendocrine Tumors: The Experience of a Single Center

PURPOSE

Peptide receptor radionuclide therapy (PRRT) is an effective and safe treatment of unresectable or metastatic, progressive neuroendocrine tumours (NETs). However, if progression occurs after the initial PRRT, treatment options remain limited. Our aim was to evaluate the efficacy and safety of a repeat 177Lutetium-[DOTA°,Tyr3]octreotate ([177Lu]Lu-DOTA-TATE) PRRT course in patients with progressive NET after the first [177Lu]Lu-DOTA-TATE PRRT (peptide receptor radionuclide therapy first treatment (PRRT1)).

METHODS

This is a nine-year retrospective observational study of 20 patients who were re-treated with PRRT (peptide receptor radionuclide therapy retreatment (PRRTR)) after PRRT1.

RESULTS

The median progression-free survival (PFS) following PRRT1 was 32 months (interquartile range (IQR): 16.5-44.5). After PRRT1, all 20 patients progressed. Of the 20 patients included, two were lost during follow-up. The median PFS after PRRTR was 17.5 months (IQR: 7-39). At the time of analysis, 15/18 patients progressed, and 3/18 had stable disease after PRRTR. Among those patients who progressed, the median time to progression was nine months (IQR: 0-17). The median overall survival from the time of the first cycle of PRRT1 was 66 months (IQR: 65-90). No significant renal or liver toxicity was reported, nor was there a drop in haemoglobin. The decrease in platelet count after PRRTR was statistically significant (p=0.03). Two cycles at PRRTR (vs. 1) were associated with a longer PFS (p=0.014) and the presence of metastases pre-PRRTR was associated with a shorter time to progression following PRRTR (p=0.04).  Conclusion: Patients who progressed after PRRT1 can achieve good PFS and minor toxicity. Our study reinforces the efficacy and safety of PRRTR and provides an analysis of factors associated with better outcomes, which can aid clinicians in clinical decision-making.

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.

Developments in 177Lu-based radiopharmaceutical therapy and dosimetry

177Lu is a radioisotope that has become increasingly popular as a therapeutic agent for treating various conditions, including neuroendocrine tumors and metastatic prostate cancer. 177Lu-tagged radioligands are molecules precisely designed to target and bind to specific receptors or proteins characteristic of targeted cancer. This review paper will present an overview of the available 177Lu-labelled radioligands currently used to treat patients. Based on recurring, active, and completed clinical trials and other available literature, we evaluate current status, interests, and developments in assessing patient-specific dosimetry, which will define the future of this particular treatment modality. In addition, we will discuss the challenges and opportunities of the existing dosimetry standards to measure and calculate the radiation dose delivered to patients, which is essential for ensuring treatments' safety and efficacy. Finally, this article intends to provide an overview of the current state of 177Lu- tagged radioligand therapy and highlight the areas where further research can improve patient treatment outcomes.

Clinical Pharmacokinetics of Radiopharmaceuticals from SPECT/CT Image Acquisition by Contouring in Patients with Gastroenteropancreatic Neuroendocrine Tumors: Lu-177 DOTATATE (Lutathera®) Case

BACKGROUND AND OBJECTIVE

Lu-177 DOTATATE (Lutathera^®) is a radiolabeled analog of somatostatin administered intravenously in patients with somatostatin receptor-positive gastroenteropancreatic neuroendocrine tumors. Biodistribution of Lu-177 DOTATATE in tumor and healthy tissues can be monitored by serial post-injection scintigraphy imaging. Patient exposure to the drug is variable with the recommended fixed dosage, and hence there is a variable response to treatment. The aim of this work was to study the pharmacokinetics of Lu-177 DOTATATE by a population modeling approach, based on single-photon emission computed tomography (SPECT)/computed tomography (CT) images used as surrogate of plasma concentrations to study the interindividual variability and finally optimize an individual dosage.

METHODS

From a retrospective study, SPECT/CT images were acquired at 4 h, 24 h, 72 h, and 192 h postadministration. From these images, volumic activities were calculated in blood and bone marrow. An individual non-compartmental pharmacokinetic analysis was performed, and the mean pharmacokinetic parameters of each tissue were compared together and with reference data. Blood volumic activities were then used to perform a population pharmacokinetic analysis (NONMEM).

RESULTS

The pharmacokinetic parameters (non-compartmental analysis) obtained from blood (clearance [CL] = 2.65 L/h, volume of distribution at steady state [Vss] = 309 L, elimination half-life [t_1/2] = 86.3 h) and bone marrow (CL =1.68 L/h, Vss = 233 L, t_1/2 = 98.8 h) were statistically different from each other and from reference values (CL = 4.50 L/h, Vss = 460 L, t_1/2 = 71.0 h) published in the literature. SPECT/CT blood images were used as a surrogate of plasma concentrations to develop a population pharmacokinetic model. Weight was identified as covariate on volume of the central compartment, reducing the interindividual variability of all population pharmacokinetic parameters.

CONCLUSION

This study is a proof of concept that obtaining pharmacokinetic parameters with image-based blood concentration is possible. Obtaining observed concentrations from SPECT/CT images, without the need for blood sampling, is a real advantage for the patient and the drug monitoring. Pharmacokinetic modeling could be combined with a deep learning model for automatic contouring and allow precise patient-specific dose adjustment in a non-invasive manner.

Integrating Theranostics Into Patient Care Pathways: AJR Expert Panel Narrative Review

Theranostics describes the coupling of a diagnostic biomarker and a therapeutic agent (i.e., a theranostic pair) that have a common target in tumor cells or their microenvironment. The term is increasingly associated with in vivo nuclear medicine oncologic applications that couple diagnostic imaging by means of gamma radiation with concomitant localized high-energy particulate radiation to a tissue expressing the common target. Several theranostic pairs have been translated into clinical practice in the United States and are poised to become a mainstay of cancer treatment. The purposes of this article are to review experience with theranostics for solid-organ malignancies and to address the practical integration into care pathways of β-emitting therapies that include somatostatin analogue radioligands for neuroendocrine tumors, PSMA-directed therapy for prostate cancer, and 131I-MIBG therapy for tumors of neural crest origin. Toxicities related to theranostics administration and indications for cessation of therapy in patients who experience adverse events are also discussed. A multidisciplinary team-based approach for identifying patients most likely to respond to these agents, determining the optimal time for therapy delivery, and managing patient care throughout the therapeutic course is critical to the success of a radiotheranostic program.

Neuroendocrine Tumor Therapy Response Assessment

Peptide receptor radionuclide therapy has become an integral part of management of neuroendocrine neoplasms. Gallium-68- and lutetium-177-labeled somatostatin receptor analogues have replaced yttrium-90- and 111-indium-based tracers. Several newer targeted therapies are also being used in clinical and research settings. It is imperative to accurately evaluate the response to these agents. The characteristics of NENs and the response patterns of the targeted therapies make response assessment in this group challenging. This article provides an overview of the strengths and weaknesses of the various biomarkers available for response assessment.

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.

Active bone marrow S-values for the low-energy electron emitter terbium-161 compared to S-values for lutetium-177 and yttrium-90

Background

Based on theoretical and preclinical results, terbium-161 may be a valid alternative to lutetium-177 and yttrium-90 in radionuclide therapies. The large low-energy electron emission from terbium-161 is a favorable feature in the treatment of disseminated disease, but its impact on the radiosensitive bone marrow needs to be evaluated. Using voxel-based skeletal dosimetry models in which active bone marrow is defined as regions containing stem cells and progenitor cells of the hematopoietic lineage, we generated S-values (absorbed dose per decay) for terbium-161 and evaluated its distribution-dependence in bone marrow cavities.

Methods

S-values in the active bone marrow were calculated for terbium-161, lutetium-177, and yttrium-90 irradiation using two (male/female) image-based bone marrow dosimetry models. The radionuclides were distributed to one of the three structures that define the spongiosa bone region in the skeletal models: (i) active bone marrow, (ii) inactive bone marrow, or (iii) surface or whole volume of the trabecular bone. Decay data from ICRP 107 were combined with specific absorbed fractions to calculate S-values for 13 skeletal sites. To increase the utility, the skeletal site-specific S-values were averaged to produce whole-body average S-values and spongiosa average S-values.

Results

For yttrium-90, the high-energy β particles irradiate the active marrow regardless of the source compartment, consistently generating the highest S-values (65–90% higher). Between terbium-161 and lutetium-177, the largest differences in S-values were with an active marrow source (50%), such as self-irradiation, due to the contribution of the short-ranged conversion and Auger electrons from terbium-161. Their influence decreased as the source moved to inactive marrow or the surface or volume of the trabecular bone, reducing the S-values and the differences between terbium-161 and lutetium-177 (15–35%).

Conclusion

The S-values of terbium-161 for active bone marrow and, consequently, the bone marrow toxicity profile were more dependent on the radionuclide distribution within the bone marrow cavity than the S-values of lutetium-177 and yttrium-90. This effect was attributed to the considerable low-energy electron emission of terbium-161. Therefore, it will be critical to investigate the bone marrow distribution of a particular radiopharmaceutical for accurate estimation of the active bone marrow dose.

Temozolomide duration and secondary hematological neoplasms: A literature review and implications for patients with neuroendocrine neoplasms

Evidence-based recommendations for the optimal duration and sequencing of temozolomide-based treatments in advanced neuroendocrine neoplasms are lacking. Here, we conducted a systematic review of the literature for a descriptive analysis of temozolomide-associated myelodysplasias and leukemias to guide treatment planning. A database search of PubMed and Embase was conducted to identify case reports and/or case series reporting secondary myelodysplasias or leukemias in the setting of temozolomide therapy. Key data items extracted from the studies were the temozolomide dose and duration, latency to hematological disorder, type of secondary malignancy and cytogenetics. Reported cases were summarized graphically. A total of 16 studies with 27 patient cases of therapy-related hematologic neoplasms were identified, all of which were case reports or case series. The median treatment duration and cumulative dose were 19 months and 18,000 mg/m² , respectively. Most patients (21/27) were diagnosed on, or after, 12 months, while only one patient was diagnosed before 6 months of treatment. Most of the patients were diagnosed, while still on treatment with temozolomide. Graphically, cases clustered around a cumulative dose of 10,000 to 30,000 mg/m² and a latency period of 10 to 40 months which translates to an approximate treatment duration of 12.5 to 37.5 months. Taken together, most reported treatment-related hematological neoplasms appear to develop on or beyond the 12-month mark, while patients are still on treatment with temozolomide. For patients with neuroendocrine neoplasms, where sequencing of multiple therapies is important, we suggest an approach to optimizing treatment duration by establishing disease response at 6 months before continuing further treatment and restricting treatment to or establishing closer vigilance beyond 12 months.

Severe Thrombocytopenia in Patients With Advanced Neuroendocrine Tumor Treated With Peptide Receptor Radioligand Therapy

BACKGROUND

Peptide receptor radioligand therapy (PRRT) was Food and Drug Administration approved in 2018 for the treatment of unresectable somatostatin receptor-positive gastroenteropancreatic neuroendocrine tumors (NETs) and provides an important option for patients with advanced disease. A known adverse effect of this treatment is hematologic toxicity, although usually transient. We present 3 patients with metastatic gastroenteropancreatic NETs treated with PRRT who were evaluated for severe persistent thrombocytopenia.

METHODS

Three patients who commenced therapy with PRRT were known to proceed to a bone marrow (BM) biopsy for persistent severe thrombocytopenia and were included in this study. These patients were identified retrospectively and evaluated for their tumor properties, including immunohistochemical markers, treatment modalities, and clinical outcomes.

RESULTS

All 3 patients had metastatic NETs that progressed on prior lines of therapy and were treated with 1 to 4 doses of 177Lu-DOTATATE 7.4 GBq (200 mCi) before developing grade 3 (25,000 to 50,000/μL) refractory thrombocytopenia. All patients had concurrent bone metastases, and 2 of the 3 had baseline grade 1 thrombocytopenia. In all 3 cases, BM biopsy documented widespread tumor infiltration.

CONCLUSIONS

Severe refractory thrombocytopenia after PRRT is rare and may result from numerous known causes, including radiation-induced myelotoxicity, myelodysplastic syndrome, and tumor BM infiltration. We present 3 cases of thrombocytopenia related to persistent or progressive BM metastasis. Although known bone metastasis is not a contraindication to PRRT, thrombocytopenia may be a manifestation of tumor progression and should be considered when making decisions about continuation of therapy.

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.

Efficacy and safety of 177Lu‑DOTATATE in patients with advanced pancreatic neuroendocrine tumours: data from the NETTER-R international, retrospective study

Purpose

NETTER-R aimed to determine the efficacy, safety and tolerability of ¹⁷⁷Lu-DOTATATE in patients with progressive, advanced pancreatic neuroendocrine tumours (panNETs) using retrospective real-world data from multiple sites.

Methods

This international study retrospectively included patients with panNETs treated with ¹⁷⁷Lu-DOTATATE. The primary endpoint was progression-free survival (PFS) by Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST v1.1). Secondary endpoints included overall survival (OS), safety and tumour response.

Results

In total, 110 patients with panNETs were studied; 65.5% received a cumulative dose of ¹⁷⁷Lu-DOTATATE 29.6 GBq ± 10% (median: 7.4 GBq). In 62 patients with available RECIST v1.1 tumour response, the median PFS was 24.8 months (95% confidence interval [CI]: 17.5–34.5), and the objective response rate was 40.3% (95% CI: 28.1–53.6); all responses were partial. With a median follow up of 24.5 months (range: 2.0–123.4 months) after the first cycle of ¹⁷⁷Lu-DOTATATE, the median OS in the full analysis set (n = 110) was 41.4 months (95% CI: 28.6–50.2). PFS (hazard ratio [HR]: 3.672; p = 0.0009) and OS (HR: 3.360; p < 0.0001) were longer in patients who received no chemotherapy prior to ¹⁷⁷Lu-DOTATATE than those who did. No treatment-emergent adverse events (TEAEs) led to treatment discontinuation. Grade 3 anaemia, lymphopenia and thrombocytopenia occurred in 0.9%, 5.4% and 0.9% of patients, respectively. No acute leukaemia or myelodysplastic syndrome was reported. Six patients (5.5%) had renal TEAEs. All renal grade ≥ 3 events were transient and did not lead to treatment modification.

Conclusions

These results reinforce the role of ¹⁷⁷Lu-DOTATATE for the treatment of patients with advanced, somatostatin receptor-positive panNETs.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00259-022-05771-3.

Treatment of neuroendocrine tumours with 177 Lu-peptide receptor radionuclide therapy: Challenging clinical scenarios and their management

Peptide receptor radionuclide therapy (PRRT) for the treatment of patients with neuroendocrine tumours is usually well tolerated, with selection based on existing guidelines. However, there are various scenarios where the risk-benefit analysis of PRRT needs to be evaluated to limit any complications associated with PRRT. This review looks at 11 key scenarios where the risk-benefit of PRRT needs to be closely evaluated.

Lutetium-177 Dotatate-Induced Hemolytic Anemia and Myelodysplastic Syndrome

Lutetium-177 (¹⁷⁷Lu) dotatate is a type of peptide receptor radioligand therapy (PRRT) using radiolabeled somatostatin for patients with progressive somatostatin receptor-positive gastrointestinal neuroendocrine tumors. While cases of therapy-related myeloid neoplasms (t-MN) have been described as a consequence of ¹⁷⁷ Lu dotatate, there are no reports of hemolytic anemia associated with therapy. We present a case of a 68-year-old woman with metastatic low-grade neuroendocrine tumor who presented four weeks after the second dose of ¹⁷⁷Lu dotatate with progressive fatigue and dyspnea. Laboratory workup was remarkable for hemolytic anemia. Lutetium-177 dotatate-induced hemolysis was suspected after ruling out other causes. Corticosteroid treatment was initiated with improvement in hemoglobin, and dose-reduced PRRT was planned upon discharge. Six months into the treatment course of ¹⁷⁷Lu dotatate, macrocytic anemia was noticed on routine follow-up with normal vitamin B12 and folic acid levels. A bone marrow biopsy was done, revealing myelodysplastic syndrome (MDS) features. Given the temporal relationship between drug introduction and the objective findings, early-onset ¹⁷⁷Lu dotatate-induced MDS was diagnosed with a plan for close hematologic follow-up. Myelodysplastic syndrome should be suspected when megaloblastic anemia develops in patients with previous ¹⁷⁷Lu dotatate therapy. The latency period between initial treatment and MDS diagnosis reported in the literature ranges between 15 months to seven years. Apart from the unusually early onset of MDS, what is unique about our case is the development of hemolytic anemia after administration of PRRT. The clinical course and the brisk response to steroid therapy, suggest other mechanisms of PRRT toxicity besides DNA breaks, genetic mutations, and myelosuppression by an immune-mediated component that likely plays a role in ¹⁷⁷Lu dotatate toxicity. Further investigation and monitoring are needed to identify the frequency of such adverse events and the pathophysiology of their occurrence.

Early Complications of Radioisotope Therapy with Lutetium-177 and Yttrium-90 in Patients with Neuroendocrine Neoplasms-A Preliminary Study

Neuroendocrine neoplasms (NENs) constitute a heterogenous group of tumors originating from neuroendocrine cells scattered throughout the body. Peptide Receptor Radionuclide Therapy (PRRT) is a treatment of choice of unresectable metastasized progressive and well-differentiated NENs. The aim of the study was to assess early bone marrow and kidney injury after administration of Lutetium-177 or Lutetium-177 combined with Yttrium-90. Thirty-one patients received treatment with [¹⁷⁷Lu]Lu-DOTATATE with the activity of 7.4 GBq. Eleven patients received tandem treatment with [⁹⁰Y]Y-DOTATATE with the activity of 1.85 GBq + [¹⁷⁷Lu]Lu-DOTATATE with the activity of 1.85 GBq. After PRRT a significant decrease in leukocyte, neutrophil, and lymphocyte counts was noted. Tandem treatment demonstrated a more marked decrease in white blood cell count compared to Lutetium-177 therapy only. Conversely, no significant influence on glomerular filtration was found in this assessment. However, PRRT triggered acute renal tubule dysfunction, regardless of the treatment type. Regarding the acute complications, PRRT appeared to be a safe modality in the treatment of patients with NEN.

Treatment patterns and oncological outcome of patients with advanced small intestinal neuroendocrine tumors: real-world data from the Medical University of Vienna

Background:

Different oncological therapies have been approved for small intestinal neuroendocrine tumors (SI-NETs), but relatively little is known about efficacy and long-term outcome outside of phase III trials.

Methods:

This retrospective analysis assessed patients with well-differentiated, metastatic SI-NETs treated at the Medical University of Vienna, an approved European Neuroendocrine Tumor Society (ENETS) Center of Excellence for neuroendocrine tumors. The primary objective was to assess progression-free survival (PFS) following approved therapies, that is, octreotide, lanreotide, peptide receptor radionuclide therapy (PRRT), and everolimus, in a representative real-world collective.

Results:

A total of 77 patients receiving systemic treatment for advanced SI-NETs between 2010 and 2021 were included, with a median follow-up time of 82.3 months [95% confidence interval (CI), 57.8–106.8 months]. In the entire collective, the estimated median PFS following first-line therapy was 32.0 months (95% CI, 23.5–40.5 months). Peritoneal carcinomatosis was significantly associated with worse PFS ( p = 0.016). Regarding therapeutic strategies and outcome, 59 patients received somatostatin analogs first line and no significant difference in PFS was observed between lanreotide and octreotide (29.3 versus 35.5 months, p = 0.768). Across all treatment lines, 42 patients underwent PRRT (estimated median PFS: 32.0 months; 95% CI, 25.6–38.3 months) and a small subgroup of 7 patients received everolimus (estimated median PFS: 9.2 months; 95% CI, 1.6–17.0 months). For the total cohort, the estimated median OS following first-line therapy was 100.6 months (95% CI, 82.3–118.8 months), but the high proportion of deaths attributed to NET (77.8%) underlines the lethal nature of the disease. No unexpected toxicities were observed.

Conclusions:

While peritoneal carcinomatosis emerged as an adverse prognostic factor for PFS in this collective, the long-term outcome of patients treated at a specialized NET center using approved therapies appeared comparable to pivotal studies in SI-NET.

OUP accepted manuscript

Background

The aim of this study was to provide a guidance for the management of neuroendocrine tumors (NETs) in clinical practice.

Material and Methods

Nominal group and Delphi techniques were used. A steering committee of 8 experts reviewed the current management of NETs, identified controversies and gaps, critically analyzed the available evidence, and formulated several guiding statements for clinicians. Subsequently, a panel of 26 experts, was selected to test agreement with the statements through 2 Delphi rounds. Items were scored on a 4-point Likert scale from 1 = totally agree to 4 = totally disagree. The agreement was considered if ≥75% of answers pertained to Categories 1 and 2 (consensus with the agreement) or Categories 3 and 4 (consensus with the disagreement).

Results

Overall, 132 statements were proposed, which incorporated the following areas: (1) overarching principles; (2) progression and treatment response criteria; (3) advanced gastro-enteric NETs; (4) advanced pancreatic NETs; (5) advanced NETs in other locations; (6) re-treatment with radioligand therapy (RLT); (7) neoadjuvant therapy. After 2 Delphi rounds, only 4 statements lacked a clear consensus. RLT was not only recommended in the sequencing of different NETs but also as neoadjuvant treatment, while several indications for retreatment with RLT were also established.

Conclusion

This document sought to pull together the experts’ attitudes when dealing with different clinical scenarios of patients suffering from NETs, with RLT having a specific role where evidence-based data are limited.

Matching-adjusted indirect treatment comparison of [177Lu]Lu-DOTA-TATE, everolimus and sunitinib in advanced, unresectable gastroenteropancreatic neuroendocrine tumours: Relative effectiveness of [177Lu]Lu-DOTA-TATE in gastroenteropancreatic neuroendocrine tumours

Head-to-head comparisons of the efficacy of treatments for gastroenteropancreatic neuroendocrine tumours (GEP-NETs) have not yet been reported. This study used a series of matching-adjusted indirect comparisons to indirectly compare the effectiveness of [¹⁷⁷Lu]Lu-DOTA-TATE to everolimus, sunitinib and best supportive care (BSC) for extending progression-free survival and overall survival in patients with advanced, unresectable gastrointestinal (GI)-NETs and P-NETs. The results of the main analysis suggest that after accounting for differences in key prognostic variables, the hazard of progression was 62% (hazard ratio [HR], 0.38; confidence interval [CI]₉₅ 0.25–0.58) and 65% (HR 0.35 CI₉₅ 0.21–0.59) lower in patients with GI-NETs treated with [¹⁷⁷Lu]Lu-DOTA-TATE than in those treated with everolimus and BSC, respectively. Similarly, the hazard of progression was 64% (HR 0.36 CI₉₅ 0.18–0.70), 54% (HR 0.46 CI₉₅ 0.30–0.71) and 79–87% (HR 0.21 CI₉₅ 0.13–0.32; HR 0.13 CI₉₅ 0.08–0.22) lower in patients with P-NET treated with [¹⁷⁷Lu]Lu-DOTA-TATE than in those treated with sunitinib, everolimus and BSC, respectively. The hazard of death was 58% (HR 0.42 CI₉₅ 0.25–0.72), 47% (HR 0.53 CI₉₅ 0.33–0.87) and 44–64% (HR 0.56 CI₉₅ 0.36–0.90; HR 0.34 CI₉₅ 0.20–0.57) lower in P-patients with NET treated with [¹⁷⁷Lu]Lu-DOTA-TATE than in those treated with sunitinib, everolimus and BSC, respectively. While our results must be interpreted with caution given the non-randomised nature of the comparisons and the potential for residual confounding, the magnitude of the effect sizes we observe and their consistency across comparators suggest that [¹⁷⁷Lu]Lu-DOTA-TATE may be a more effective treatment option than everolimus, sunitinib and BSC in advanced, unresectable GEP-NETs.

•

The study reports unanchored indirect comparisons of treatments in GI- and P-NETs.

•

177Lu-DOTATATE was compared with everolimus, sunitinib and supportive care.

•

GI- and P-NETs patients treated with 177Lu-DOTATATE had lower hazard of progression.

•

Patients with P-NET treated with 177Lu-DOTATATE had lower hazard of death.

•

Results must be interpreted with caution given potential for residual confounding.

Dosimetry in Clinical Radiopharmaceutical Therapy of Cancer: Practicality Versus Perfection in Current Practice

The use of radiopharmaceutical therapies (RPTs) in the treatment of cancers is growing rapidly, with more agents becoming available for clinical use in last few years and many new RPTs being in development. Dosimetry assessment is critical for personalized RPT, insofar as administered activity should be assessed and optimized in order to maximize tumor-absorbed dose while keeping normal organs within defined safe dosages. However, many current clinical RPTs do not require patient-specific dosimetry based on current Food and Drug Administration-labeled approvals, and overall, dosimetry for RPT in clinical practice and trials is highly varied and underutilized. Several factors impede rigorous use of dosimetry, as compared with the more convenient and less resource-intensive practice of empiric dosing. We review various approaches to applying dosimetry for the assessment of activity in RPT and key clinical trials, the extent of dosimetry use, the relative pros and cons of dosimetry-based versus fixed activity, and practical limiting factors pertaining to current clinical practice.

177Lu-Dotatate plus long-acting octreotide versus high‑dose long-acting octreotide in patients with midgut neuroendocrine tumours (NETTER-1): final overall survival and long-term safety results from an open-label, randomised, controlled, phase 3 trial

BACKGROUND

The primary analysis of the phase 3 NETTER-1 trial showed significant improvement in progression-free survival with ¹⁷⁷Lu-Dotatate plus long-acting octreotide versus high-dose long-acting octreotide alone in patients with advanced midgut neuroendocrine tumours. Here, we report the prespecified final analysis of overall survival and long-term safety results.

METHODS

This open-label, randomised, phase 3 trial enrolled patients from 41 sites in eight countries across Europe and the USA. Patients were 18 years and older with locally advanced or metastatic, well differentiated, somatostatin receptor-positive midgut neuroendocrine tumours (Karnofsky performance status score ≥60) and disease progression on fixed-dose long-acting octreotide. Patients were randomly assigned (1:1) via an interactive web-based response system to intravenous ¹⁷⁷Lu-Dotatate 7·4 GBq (200 mCi) every 8 weeks (four cycles) plus intramuscular long-acting octreotide 30 mg (¹⁷⁷Lu-Dotatate group) or high-dose long-acting octreotide 60 mg every 4 weeks (control group). The primary endpoint of progression-free survival has been previously reported; here, we report the key secondary endpoint of overall survival in the intention-to-treat population. Final overall survival analysis was prespecified to occur either after 158 deaths or 5 years after the last patient was randomised, whichever occurred first. During long-term follow-up, adverse events of special interest were reported in the ¹⁷⁷Lu-Dotatate group only. This trial is registered with ClinicalTrials.gov, NCT01578239.

FINDINGS

From Sept 6, 2012, to Jan 14, 2016, 231 patients were enrolled and randomly assigned for treatment. The prespecified final analysis occurred 5 years after the last patient was randomly assigned (when 142 deaths had occurred); median follow-up was 76·3 months (range 0·4-95·0) in the ¹⁷⁷Lu-Dotatate group and 76·5 months (0·1-92·3) in the control group. The secondary endpoint of overall survival was not met: median overall survival was 48·0 months (95% CI 37·4-55·2) in the ¹⁷⁷Lu-Dotatate group and 36·3 months (25·9-51·7) in the control group (HR 0·84 [95% CI 0·60-1·17]; two-sided p=0·30). During long-term follow-up, treatment-related serious adverse events of grade 3 or worse were recorded in three (3%) of 111 patients in the ¹⁷⁷Lu-Dotatate group, but no new treatment-related serious adverse events were reported after the safety analysis cutoff. Two (2%) of 111 patients given ¹⁷⁷Lu-Dotatate developed myelodysplastic syndrome, one of whom died 33 months after randomisation (this person was the only the only reported ¹⁷⁷Lu-Dotatate treatment-related death). No new cases of myelodysplastic syndrome or acute myeloid leukaemia were reported during long-term follow-up.

INTERPRETATION

¹⁷⁷Lu-Dotatate treatment did not significantly improve median overall survival versus high-dose long-acting octreotide. Despite final overall survival not reaching statistical significance, the 11·7 month difference in median overall survival with ¹⁷⁷Lu-Dotatate treatment versus high-dose long-acting octreotide alone might be considered clinically relevant. No new safety signals were reported during long-term follow-up.

FUNDING

Advanced Accelerator Applications, a Novartis company.

Value of Peptide Receptor Radionuclide Therapy as Neoadjuvant Treatment in the Management of Primary Inoperable Neuroendocrine Tumors

INTRODUCTION

Neuroendocrine neoplasms including neuroendocrine tumors (NETs) are often diagnosed as primary disseminated or inoperable. In those cases, systemic extensive therapy is necessary, but radical treatment is unlikely. As described in the literature, in some selected cases, peptide receptor radionuclide therapy (PRRT) may be used as a first-line/neoadjuvant therapy that allows further successful surgery. Such treatment may enable a reduction of total tumor burden or allow a radical treatment which improves the final outcomes.

AIM

This study aims to assess whether neoadjuvant PRRT could be a treatment option for patients with initially unresectable NETs.

METHODS

Among the group of 114 patients treated with PRRT between the years 2005 and 2020, in 32 cases, it was the first-line therapy, mainly due to massive disease burden at the time of diagnosis. Among them, nine patients received PRRT as the first-line treatment due to the primary inoperable tumors with the intention of preoperative reduction of the tumor size in order to allow for a surgical treatment.

RESULTS

Neoadjuvant PRRT enabled surgery in four out of nine (45%) patients. Finally, in two out of four cases, the goal (radical surgery) has been achieved.

CONCLUSION

PRRT may be considered not only as a palliative but also as a neoadjuvant therapy in advanced, somatostatin-positive NETs that were initially inoperable.

Prophylactic Peripheral Blood Stem Cell Collection in Patients with Extensive Bone-Marrow Infiltration of Neuroendocrine Tumours Prior to Peptide Receptor Radionuclide Therapy with 177Lu-DOTATATE

Peptide receptor radionuclide therapy (PRRT) of metastatic neuroendocrine tumors (NET) can be successfully repeated but may eventually be dose-limited. Since ¹⁷⁷Lu-DOTATATE dose limitation may come from hematological rather than renal function, hematological peripheral blood stem cell backup might be desirable. Here, we report our initial experience of peripheral blood stem-cell collection (PBSC) in patients with treatment-related cytopenia and therefore high risk of bone-marrow failure. Five patients with diffuse bone-marrow infiltration of NET and relevant myelosuppression (≥grade 2) received PBSC before one PRRT cycle with ¹⁷⁷Lu-DOTATATE (7.6 ± 0.8 GBq/cycle). Standard stem-cell mobilization with Granulocyte-colony stimulating factor (G-CSF) was applied, and successful PBSC was defined as a collection of >2 × 10⁶/kg CD34+ cells. In case of initial failure, Plerixafor was administered in addition to G-CSF prior to apheresis. PBSC was successfully performed in all patients with no adverse events. Median cumulative activity was 44.8 GBq (range, 21.3-62.4). Three patients had been previously treated with PRRT, two of which needed the addition of Plerixafor for stem-cell mobilization. Only one of five patients required autologous peripheral blood stem-cell transplantation during the median follow up time of 28 months. PBSC collection seems to be feasible in NET with bone-marrow involvement and might be worth considering as a backup strategy prior to PRRT, in order to overcome dose-limiting bone-marrow toxicity.

Salvage Radioligand Therapy with Repeated Cycles of 177Lu-PSMA-617 in Metastatic Castration-Resistant Prostate Cancer with Diffuse Bone Marrow Involvement

Simple Summary

Metastatic castration-resistant prostate cancer (mCRPC) with extensive spread to the bone marrow is an incurable stage of disease associated with a poor prognosis and a high risk of impaired blood cell formation. Therapeutic options prolonging survival are limited and may result in significant bone marrow toxicity. The concept of radioligand therapy (RLT) in mCRPC is marked by the targeted delivery of radionuclides, such as beta particle emitting ¹⁷⁷Lutetium (¹⁷⁷Lu) to the prostate-specific membrane antigen (PSMA), a transmembrane protein frequently present on prostate cancer cells. RLT has yielded promising anti-tumoral activity and excellent tolerability in patients with mCRPC as shown by multiple retrospective series and a growing number of prospective trials. The presented study aims to investigate the role of RLT in mCRPC patients with metastases diffusely involving the bone marrow. Special emphasis is laid on identifying early indicators for a favorable treatment response and potential risk factors for adverse outcomes. The impact of RLT-specific variables, including administered treatment activity, cumulative activity and whole-body absorbed dose is assessed individually.

Abstract

Advanced stage metastatic prostate cancer with extensive bone marrow involvement is associated with a high risk of therapy-induced myelotoxicity and unfavorable outcomes. The role of salvage radioligand therapy (RLT) with ¹⁷⁷Lu-PSMA-617 in this subset of patients remains to be further elucidated. Forty-five patients with progressive metastatic castration-resistant prostate cancer (mCRPC) and diffuse bone marrow involvement were treated with repeated cycles of RLT after having exhausted standard treatment options. A mean treatment activity of 7.4 ± 1.4 GBq ¹⁷⁷Lu-PSMA-617 was administered in a median of four treatment cycles (IQR 2-6) and the mean cumulative activity was 32.6 ± 20.1 GBq. After two RLT cycles, ≥50% PSA decline was observed in 25/45 (56%) patients and imaging-based partial remission (PR) was observed in 18/45 (40%) patients. Median imaging-based progression-free survival (PFS) was 6.4 mo (95% CI, 3.0–9.8) and the median overall survival (OS) was 10.2 months (95% CI, 7.2–12.8). The biochemical response translated into a significantly prolonged PFS (12.9 vs. 2.8 mo, p < 0.001) and OS (13.5 vs. 6.7 mo, p < 0.001). Patients with PR on interim imaging after two cycles had a longer median OS compared to patients with stable or progressive disease (15.5 vs. 7.1 mo, p < 0.001). Previous taxane-based chemotherapy (HR 3.21, 95%CI 1.18–8.70, p = 0.02) and baseline LDH levels (HR 1.001, 95%CI 1.000–1.001, p = 0.04) were inversely associated with OS on a Cox-regression analysis. Grade ≥ 3 hematological decline was observed after 22/201 (11%) cycles with anemia, leukopenia and thrombocytopenia in 15/45 (33%), 6/45 (13%) and 8/45 (18%) patients, respectively. Cumulative treatment activity and absorbed whole-body dose were not correlated with new onset grade ≥ 3 hematotoxicity (p = 0.91, p = 0.69). No event of grade ≥ 3 chronic kidney disease was observed during RLT or the follow-up. Last line RLT with ¹⁷⁷Lu-PSMA-617 in mCRPC patients with diffuse bone marrow involvement may thus contribute to prolonged disease control at an acceptable safety profile.

Finding the Appropriate Therapeutic Strategy in Patients with Neuroendocrine Tumors of the Pancreas: Guideline Recommendations Meet the Clinical Reality

The systemic treatment of patients with pancreatic neuroendocrine tumors is based on placebo-controlled trials and long-established chemotherapy approaches. In addition, peptide receptor radionuclide therapy (PRRT) was approved as a parallel approach for pancreatic neuroendocrine tumors (NET), in addition to small bowel NET, after the NETTER-1 trial. The current ESMO and NCCN guidelines attempted to describe treatment algorithms for pancreatic NET based on the current data. In our survey, we recorded therapy decisions for the first- until the third-line of therapy in German-speaking countries (Germany, Austria, and Switzerland) using fictional case reports and discussed these in the context of the current ESMO guidelines. Compared with the recommendations of the guidelines, PRRT was used more frequently and earlier. In patients with NET G1/G2 Ki-67 < 10%, the therapy algorithm consisting of somatostatin analogs (SSA)-PRRT-targeted therapy is a relevant approach. In clinical situations where chemotherapy is primarily used (remission pressure, Ki-67 > 10%), second-line PRRT was found acceptance and was often considered prior to targeted therapies. Despite the lack of prospective controlled trials, our study demonstrated the pivotal impact of PRRT. Therefore, further studies should compare PRRT with chemotherapy in pancreatic NETs in different clinical settings in first- and second-line approaches.

Hematologic safety of 177Lu-PSMA-617 radioligand therapy in patients with metastatic castration-resistant prostate cancer

BACKGROUND

Myelosuppression is a potential dose-limiting factor in radioligand therapy (RLT). This study aims to investigate occurrence, severity and reversibility of hematotoxic adverse events in patients undergoing RLT with ¹⁷⁷Lu-PSMA-617 for metastatic castration-resistant prostate cancer (mCRPC). The contribution of pretreatment risk factors and cumulative treatment activity is taken into account specifically.

METHODS

RLT was performed in 140 patients receiving a total of 497 cycles. A mean activity of 6.9 [Formula: see text] 1.3 GBq ¹⁷⁷Lu-PSMA-617 per cycle was administered, and mean cumulative activity was 24.6 [Formula: see text] 15.9 GBq. Hematological parameters were measured at baseline, prior to each treatment course, 2 to 4 weeks thereafter and throughout follow-up. Toxicity was graded based on Common Terminology Criteria for Adverse Events v5.0.

RESULTS

Significant (grade ≥ 3) hematologic adverse events occurred in 13 (9.3%) patients, with anemia in 10 (7.1%), leukopenia in 5 (3.6%) and thrombocytopenia in 6 (4.3%). Hematotoxicity was reversible to grade ≤ 2 through a median follow-up of 8 (IQR 9) months in all but two patients who died from disease progression within less than 3 months after RLT. Myelosuppression was significantly more frequent in patients with pre-existing grade 2 cytopenia (OR: 3.50, 95%CI 1.08-11.32, p = 0.04) or high bone tumor burden (disseminated or diffuse based on PROMISE miTNM, OR: 5.08, 95%CI 1.08-23.86, p = 0.04). Previous taxane-based chemotherapy was associated with an increased incidence of significant hematotoxicity (OR: 4.62, 95%CI 1.23-17.28, p = 0.02), while treatment with ²²³Ra-dichloride, cumulative RLT treatment activity and activity per cycle were not significantly correlated (p = 0.93, 0.33, 0.29).

CONCLUSION

Hematologic adverse events after RLT have an acceptable overall incidence and are frequently reversible. High bone tumor burden, previous taxane-based chemotherapy and pretreatment grade 2 cytopenia may be considered as risk factors for developing clinically relevant myelosuppression, whereas cumulative RLT activity and previous ²²³Ra-dichloride treatment show no significant contribution to incidence rates.

Current Status and Trends in Peptide Receptor Radionuclide Therapy in the Past 20 Years (2000-2019): A Bibliometric Study

Background: Peptide receptor radionuclide therapy (PRRT) is an emerging therapeutic option for the treatment of neuroendocrine tumors (NETs), and the number of publications in this field has been increasing in recent years. The aim of the present study was to present the research status and summarize the key topics through bibliometric analysis of published PRRT literature.

Methods: A literature search for PRRT research from 2000 to 2019 was conducted using the Science Citation Index Expanded of Web of Science Core Collection (limited to SCIE) on August 4, 2020. The VOSviewer, R-bibliometrix, and CiteSpace software were used to conduct the bibliometric analysis.

Results: From 2000 to 2019, a total of 681 publications (523 articles and 158 reviews) were retrieved. Annual publication outputs grew from three to 111 records. Germany had the largest number of publications, making the largest contribution to the field (n = 151, 22.17%). Active cooperation between countries/regions was observed. Kwekkeboom from the Erasmus Medical Center is perhaps a key researcher in the field of PRRT. The European Journal of Nuclear Medicine and Molecular Imaging and Journal of Nuclear Medicine ranked first for productive (n = 84, 12.33%) and co-cited (n = 3,438) journals, respectively. Important topics mainly included matters related to the efficacy of PRRT (e.g., ⁹⁰Y-dotatoc and ¹⁷⁷Lu-dotatate), the long-term adverse effects of PRRT (e.g., hematologic and renal toxicities), standardization of NETs and PRRT in practice, the development of medical imaging techniques, and the individual dose optimization of PRRT.

Conclusion: Using bibliometric analysis, we gained deep insight into the global status and trends of studies investigating PRRT for the first time. The PRRT field is undergoing a period of rapid development, and our study provides a valuable reference for clinical researchers and practitioners.

Somatostatin Receptor-Targeted Radiopeptide Therapy in Treatment-Refractory Meningioma: Individual Patient Data Meta-analysis

Somatostatin receptor (SSTR)-targeted peptide receptor radionuclide therapy (PRRT) represents a promising approach for treatment-refractory meningiomas. Methods: We performed an individual patient data meta-analysis, including all published data on meningioma patients treated with SSTR-targeted PRRT. The main outcomes were toxicity, response to treatment, progression-free survival (PFS), and overall survival (OS). We applied the Kaplan-Meier method to estimate survival probabilities and report incidence rates per 100 person-years. We applied Cox proportional hazards models to determine the effect of covariates. Results: We screened 537 papers and identified 6 eligible cohort studies. We included a total of 111 patients who had treatment-refractory meningioma and received SSTR-targeted PRRT. Disease control was achieved in 63% of patients. The 6-mo PFS rates were 94%, 48%, and 0% for World Health Organization grades I, II, and III, respectively. The risk of disease progression decreased by 13% per 1,000-MBq increase in the total applied activity. The 1-y OS rates were 88%, 71%, and 52% for World Health Organization grades I, II, and III, respectively. The risk of death decreased by 17% per 1,000-MBq increase in the total applied activity. The main side effects comprised transient hematotoxicity, such as anemia in 22% of patients, leukopenia in 13%, lymphocytopenia in 24%, and thrombocytopenia in 17%. Conclusion: To our knowledge, this individual patient data meta-analysis represents the most comprehensive analysis of the benefits of and adverse events associated with SSTR-targeted PRRT for treatment-refractory meningioma. The treatment was well tolerated, achieved disease control in most cases, and showed promising results regarding PFS and OS.

Second primary neoplasms in patients with lung and gastroenteropancreatic neuroendocrine neoplasms: Data from a retrospective multi-centric study

BACKGROUND

Patients with sporadic neuroendocrine neoplasms may exhibit a higher risk of a second primary tumor than the general population.

AIM

This study aimed to analyze the occurrence of second primary malignancies.

METHODS

A retrospective cohort of 2757 patients with sporadic lung and gastro-entero-pancreatic neuroendocrine neoplasms, managed at eight Italian tertiary referral Centers, was included.

RESULTS

Between 2000 and 2019, a second primary malignancy was observed in 271 (9.8%) neuroendocrine neoplasms patients with 32 developing a third tumor. There were 135 (49.8%) females and the median age was 64 years. The most frequent locations of the second tumors were breast (18.8%), prostate (12.5%), colon (9.6%), blood tumors (8.5%), and lung (7.7%). The second primary tumor was synchronous in 19.2% of cases, metachronous in 43.2%, and previous in 37.6%. As concerned the neuroendocrine neoplasms, the 5- and 10-year survival rates were 87.8% and 74.4%, respectively. PFS for patients with a second primary malignancy was shorter than for patients without a second primary malignancy. Death was mainly related to neuroendocrine neoplasms.

CONCLUSION

In NEN patients the prevalence of second primary malignancies was not negligible, suggesting a possible neoplastic susceptibility. Overall survival was not affected by the occurrence of a second primary malignancy.

Assessment of Therapy-Related Myeloid Neoplasms in Patients With Neuroendocrine Tumors After Peptide Receptor Radionuclide Therapy: A Systematic Review

Importance

Peptide receptor radionuclide therapy (PRRT) is a tumor-targeted treatment that uses radiation to induce tumor cell death in neuroendocrine tumors (NET) via β particle-emitting radionuclide linked to a somatostatin peptide analog. Therapy-related myeloid neoplasm (t-MN) has been reported as a potential long-term and frequently lethal adverse event after PRRT. However, the incidence, time of diagnosis, and nature of t-MN is unclear. Therefore, a systematic review is helpful to study the incidence and characteristics of t-MN after PRRT in patients with NET.

Objective

To systematically evaluate the literature and report the incidence, time of diagnosis, and nature of t-MN after PRRT.

Evidence Review

MEDLINE, Embase, Scopus, Web of Science, and Cochrane Central Register of Controlled Trials for articles and abstracts reporting studies of different designs studying more than 1 patient (randomized clinical trials, prospective phase I or phase II, retrospective studies, and case series) were searched from database inception through April 2019. Studies of interest included patients with NET who were treated with PRRT and reported the incidence of t-MN, if any. The primary outcome was the incidence of t-MN.

Findings

Twenty-eight articles were identified comprising 7334 patients who were treated with PRRT for NET. The main reason of exclusion was not reporting the t-MN incidence. The incidence of t-MN was variable between studies with mean (SD) incidence of 2.61% (4.38%). Of all 134 cases, cytogenetic abnormalities were reported in 32 patients with the most common abnormality being complex cytogenetics, consistent with myeloid neoplasms following exposure to alkylating agents or irradiation.

Conclusions and Relevance

The risk of t-MN after PRRT is small but not insignificant given the poor prognosis after t-MN diagnosis. Close monitoring is warranted to identify such patients early in the disease course when hematologic abnormalities persist.

Radiopharmaceuticals for Neuroendocrine Tumors

Neuroendocrine tumors (NETs) are a heterogeneous group of tumors that originate in endocrine tissues throughout the body. Peptide receptor radionuclide therapy (PRRT) has emerged as a promising therapeutic option for patients with locally advanced and/or metastatic disease refractory to standard of care treatment. The landmark international phase III NETTER-1 trial led to the approval of ¹⁷⁷Lu-DOTATATE (Lutathera) in the treatment of somatostatin receptor-positive gastroenteropancreatic NETs. Similarly, data from the multicenter, phase II Study IB12B led to the approval of meta-[¹³¹I]Iodo-Benzyl-Guanidine (^I31I-MIBG) for treatment of iobenguane scan-positive, unresectable, locally advanced or metastatic pheochromocytoma or paraganglioma. With the clinical approval of these novel radiopharmaceuticals for managing select patients with NETs, additional studies are needed to refine patient selection, predict and assess therapy response, and optimize radiopharmaceutical delivery and clinical outcomes.

Comparative safety review of the current therapies for gastroenteropancreatic neuroendocrine tumors

Introduction: Neuroendocrine neoplasms (NENs) comprise a heterogeneous group of neoplasms, whose management requires complex and individualized clinical decisions. Over the last decades the advent of novel medications and advanced diagnostic and therapeutic modalities, alongside our deeper understanding of the disease, revolutionized the landscape of their management, significantly improving both prognosis and quality of life of patients.Area covered: Treatment-related adverse events and safety concerns as demonstrated in clinical trials, as well as in real-world clinical practice.Expert opinion: The only true curative option for NENs remains surgery, whereas high-grade advanced neuroendocrine carcinomas should be primarily managed with platinum-based chemotherapy. For the remaining cases, that comprise the vast majority, the current armamentarium includes somatostatin analogs, interferon, telotristat ethyl, molecular targeted therapies, chemotherapy, peptide receptor radionuclide therapy, and locoregional treatment. The use of the aforementioned therapeutic options is associated with several and not uncommonly severe treatment-related adverse events. However, the benefits offered inclusive of improved prognosis, amelioration of symptoms, and better quality of life amidst others, by far outweighs any adverse event.

Salvage peptide receptor radionuclide therapy in patients with progressive neuroendocrine tumors: a systematic review and meta-analysis

OBJECTIVE

Peptide receptor radionuclide therapy (PRRT) is an effective treatment option in patients with metastatic neuroendocrine tumors (NETs). Recently, salvage PRRT has been introduced for progressing NET patients. This systematic review and meta-analysis evaluated the therapeutic efficacy, survival, and toxicity of salvage PRRT in patients with progressive NETs.

METHODS

A systematic (PubMed, Embase, Cochrane, and Scopus) were performed. To determine therapeutic efficacy, objective response rate (ORR), and disease control rate (DCR) were identified using radiologic response criteria. To determine survival, progression-free survival (PFS), and overall survival (OS) were verified. To determine toxicity, information was collected on serious (grades 3 or 4) hematologic and renal adverse events.

RESULTS

Nine articles featuring 426 patients were included in this study. Salvage PRRT achieved pooled proportions of ORR in 17.1% [95% confidence interval (CI) 11.6-23.5] and DCR in 76.9% (95% CI 72.3-81.0) of patients. Salvage PRRT demonstrated pooled estimates of PFS of 14.1 months (95% CI 12.2-15.9) and OS of 26.8 months (95% CI 18.8-34.9). Pooled proportions of hematologic and renal toxicities were 10.8% (95% CI 5.9-16.8) and 0.7% (95% CI 0.2-1.8), respectively. A subgroup direct comparison study with initial PRRT revealed that salvage PRRT showed significantly lower therapeutic efficacy (ORR and DCR, all P < 0.001) and shorter PFS (P = 0.03) despite similar hematologic toxicity (P = 0.25) and renal toxicity (P = 0.45).

CONCLUSION

Salvage PRRT is effective in patients with progressive NETs, and toxicity appeared to be similar to initial PRRT which could be a feasible treatment option.

How We Do It: A Multidisciplinary Approach to 177Lu DOTATATE Peptide Receptor Radionuclide Therapy

Lutetium 177 (¹⁷⁷Lu) DOTA-0-Tyr3-Octreotate (DOTATATE) peptide receptor radionuclide therapy (PRRT) is an effective treatment for advanced gastroenteropancreatic neuroendocrine tumors. This review presents a clinical practice workflow that has been successful since ¹⁷⁷Lu DOTATATE PRRT was approved by the U.S. Food and Drug Administration. The workflow relies heavily on the input of a multidisciplinary team and involves a nuclear medicine consultation service, tumor board, and specific preparations in advance of therapy and day-of-therapy procedures. A systematic checklist designed to ensure appropriate selection of treatment candidates and identification of any concerns to address to safely administer PRRT is provided. All patients were evaluated with gallium 68 DOTATATE PET/CT, and in cases of high-grade tumors, they were also evaluated with fluorine 18 fluorodeoxyglucose PET/CT, with imaging findings reviewed as part of the systematic checklist before PRRT. Adverse effects are discussed and imaging follow-up regimens are reviewed, including alternative diagnostic contrast materials. Approaches to multiple challenging patient scenarios are illustrated through case examples. Finally, alternative theranostic radionuclides and treatment strategies are discussed.

Peptide Receptor Radionuclide Therapy of Late-Stage Neuroendocrine Tumor Patients with Multiple Cycles of 177Lu-DOTA-EB-TATE

This study aimed to evaluate the safety and efficacy of multiple cycles of ¹⁷⁷Lu-DOTA-Evans blue (EB)-TATE peptide receptor radionuclide therapy (PRRT) at escalating doses in neuroendocrine tumors (NETs). Methods: Thirty-two NET patients were randomly divided into 3 groups and treated with escalating doses. Group A received 1.17 ± 0.09 GBq/cycle; group B, 1.89 ± 0.53 GBq/cycle; and group C, 3.97 ± 0.84 GBq/cycle. The treatment was planned for up to 3 cycles. Treatment-related adverse events were graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE), version 5.0. Treatment response was evaluated according to the European Organisation for Research and Treatment of Cancer criteria and modified PERCIST. Results: Administration of PRRT was well tolerated, without life-threatening adverse events (CTCAE grade 4). CTCAE grade 3 hematotoxicity was recorded in 1 patient (16.6%) in group B (thrombocytopenia) and 3 patients (21.4%) in group C (thrombocytopenia in 3, anemia in 1). CTCAE grade 3 hepatotoxicity (elevated aspartate aminotransferase) was recorded in 1 patient in group A (8.3%) and 1 patient in group C (7.1%). No nephrotoxicity was observed. According to the criteria of the European Organisation for Research and Treatment of Cancer, the overall disease response rates were similar in groups A, B, and C (50.0%, 50.0%, and 42.9%, respectively), and the overall disease control rates were higher in groups B (83.3%) and C (71.5%) than in group A (66.7%). According to modified PERCIST, a lower disease response rate but a similar disease control rate were found. When a comparable baseline SUV_max ranging from 15 to 40 was selected, the percentage change in SUV_max increased slightly in group A (2.1% ± 40.8%) but decreased significantly in groups B and C (-38.7% ± 10.0% and -14.7% ± 20.0%, respectively) after the first PRRT (P = 0.001) and decreased in all 3 groups after the third PRRT (groups A, B, and C: -6.9% ± 42.3%, -49.2% ± 30.9%, -11.9% ± 37.9%, respectively; P = 0.044). Conclusion: Dose escalations of up to 3.97 GBq/cycle seem to be well tolerated for ¹⁷⁷Lu-DOTA-EB-TATE. ¹⁷⁷Lu-DOTA-EB-TATE doses of 1.89 and 3.97 GBq/cycle were effective in tumor control and more effective than 1.17 GBq/cycle.

Phase I study of the 177Lu-DOTA0-Tyr3-Octreotate (lutathera) in combination with nivolumab in patients with neuroendocrine tumors of the lung

Background

Lutathera is a ¹⁷⁷Lutetium-labeled somatostatin analog approved for the treatment of gastroenteropancreatic neuroendocrine tumors (NETs). Somatostatin receptors are expressed in small cell lung cancer (SCLC). Nivolumab, an anti-PD-1 antibody, may act synergistically with lutathera to generate antitumor immunity. We conducted a phase I study of lutathera plus nivolumab in patients with advanced NETs of the lung.

Methods

Patients with relapsed/refractory extensive-stage SCLC (ES-SCLC), non-progressing ES-SCLC after first-line platinum-based chemotherapy, or advanced grade I-II pulmonary NETs were eligible. The primary objective was to determine the recommended phase 2 dose (RP2D). The phase I portion followed a standard 3+3 design, assessing two dose levels (dose level 1: lutathera 3.7 GBq every 8 weeks for four doses with nivolumab 240 mg every 2 weeks; dose level 2: lutathera 7.4 GBq every 8 weeks for four doses with nivolumab 240 mg every 2 weeks).

Results

Nine patients were enrolled (six ES-SCLC, two pulmonary atypical carcinoid, one high-grade pulmonary neuroendocrine carcinoma). No dose-limiting toxicities (DLTs) were observed at dose level 1. At dose level 2, one patient with refractory ES-SCLC developed a DLT (grade 3 rash). The most common treatment-related adverse events (TRAEs) were lymphopenia (n=7), thrombocytopenia (n=4), anemia (n=3), and nausea (n=3). The most common grade 3 TRAE was lymphopenia (n=4). Among the seven patients with measurable disease, one patient with ES-SCLC had a partial response. Two patients with pulmonary atypical carcinoid had stable disease lasting 6 months. The RP2D was dose level 2.

Conclusions

Lutathera plus nivolumab was well tolerated and showed signs of antitumor activity. This combination warrants further exploration.

Trial registration number

NCT03325816

Influence of pretreatment with everolimus or sunitinib on the subacute hematotoxicity of 177Lu-DOTATATE PRRT

Background: Peptide receptor radionuclide therapy (PRRT) is a validated treatment for somatostatin receptor overexpressing neuroendocrine tumors (NETs). The NETTER-1 trial demonstrated a pronounced positive effect on progression-free-survival compared to high dose somatostatin analogs (SSAs), with a strong tendency toward overall survival benefit. Our aim was to investigate the influence of pretreatment with everolimus and/or sunitinib on subacute hematotoxicity of PRRT. To assess the influence of prior treatment with everolimus/sunitinib might be of clinical relevance due to the link between short-term hematotoxicity and increased incidence of late hematotoxicity.Material and methods: Our single-center retrospective study enrolled all patients treated with ¹⁷⁷Lu-DOTATATE PRRT (1-4 cycles of 7.4 GBq), between November 2013 and July 2018. Patients were assigned to two groups according to their pretreatment: no targeted agents (N = 41), or targeted agents (everolimus, sunitinib or both; N = 41). The end point was subacute hematotoxicity, defined as the nadir value between the first administration until 3 months after the last administration, using the CTCAE 4.03 classification. The impact of splenectomy was also explored.Results: Eighty percent of patients had a primary gastroenteropancreatic NET. No statistically significant differences in severe subacute hematotoxicity were seen in the pretreated group vs. the naive group for hemoglobin (grade 3/4: 12% vs. 22%), neither for leucocytes (grade 3/4: 10% vs. 7%), neutrophils (grade 3/4: 5% vs. 7%), lymphocytes (grade 3/4: 49% vs. 37%) and platelets (grade 3/4: 15% vs. 15%). Furthermore, we observed significantly lower toxicity for total white blood cells, lymphocytes and platelets in the subgroup that had splenectomy (N = 12). Limitations of this study include the potential bias in lack of use of targeted agents in patients more susceptible to toxicity, and the limited number of patients and events.Conclusions: In a patient cohort with NET pretreated with everolimus and/or sunitinib, we could not demonstrate a significant effect of prior/pretreatment with everolimus and/or sunitinib on the subacute hematotoxicity of ¹⁷⁷Lu-DOTATATE PRRT.