A phase IIa trial of molecular radiotherapy with 177-lutetium DOTATATE in children with primary refractory or relapsed high-risk neuroblastoma

Whole-body effective half-life of radioiodine in children and young adults with papillary thyroid cancer

PURPOSE

The lack of radioiodine-131 (RAI) kinetic study is a serious challenge for rational dosing for children and young adults (CYAs) with papillary thyroid cancer (PTC). The present study was conducted to investigate the whole-body effective half-life (EHL) and absorbed dose in RAI ablative therapy of CYAs with PTC.

METHODS

In the period 2017-2022, all consecutive PTC patients 20 years or younger prepared for ablative RAI therapy after thyroid hormone withdrawal were prospectively recruited. Serial whole-body dose-rate measurements after administration were performed to deduce whole-body RAI retention. Calculations based on the deduced whole-body retention and the schema of Medical Internal Radiation Dosimetry were derived to determine whole-body EHL and absorbed doses. A multivariate linear regression analysis was employed to assess the association between whole-body EHL and potential predictors.

RESULTS

A total of 52 patients (median age 17 years [range, 6-20 years]) were recruited. The mean whole-body EHL (±SD) was 10.3 (3.3) hours (median, 9.4 h [range, 6.3-21.7 h]). In univariable linear regression analysis, whole-body EHL was significantly associated with gender, body surface area (BSA) and body mass index (p < 0.05). Creatinine, Cystatin C, glomerular filtration rate (GFR) and positive post-ablation scintigraphy approached significance with respect to EHL (p ≤ 0.2 and ≥0.05). At multivariable analysis, BSA, GFR and positive post-ablation scintigraphy was associated with EHL. A median activity of 3.7 GBq of RAI (range, 1.85-7.40 GBq) was administered and a median whole-body absorbed dose of 0.22 Gy was delivered (range, 0.11-0.79 Gy).

CONCLUSION

A wide variation of whole-body EHL was observed in CYAs with PTC treated with RAI. The whole-body EHL is significantly longer in CYAs with larger BSA, decreased GFR and presence of extra-thyroidal disease. Understanding these predictors may improve our ability to dosing strategies in RAI therapy of CYAs with PTC.

Safety and dosimetry of [177Lu]Lu-DOTA-TATE in adolescent patients with somatostatin receptor-positive gastroenteropancreatic neuroendocrine tumours, or pheochromocytomas and paragangliomas: Primary analysis of the Phase II NETTER-P study

PURPOSE

NETTER-P, an open-label Phase II study, evaluated the safety and dosimetry of [177Lu]Lu-DOTA-TATE (hereafter 177Lu-DOTATATE) in adolescents with advanced, somatostatin receptor-positive, well-differentiated, Grade 1/2 gastroenteropancreatic neuroendocrine tumours (GEP-NET) or pheochromocytoma and paragangliomas (PPGL).

METHODS

Patients (12-17 years old) received four cycles of 177Lu-DOTATATE (7.4 GBq every 8 ± 1 weeks; cumulative administered activity: 29.6 GBq). Primary endpoints were absorbed dose (kidneys and bone marrow) and safety after first administration. Safety during treatment and comparative assessments of dosimetry and pharmacokinetics between adolescents and historical adult patients were evaluated.

RESULTS

Eleven patients (4 GEP-NET, 7 PPGL; median age 15 [range, 13-17] years) were enrolled and received ≥ 1 administration of 177Lu-DOTATATE. Median (range) cumulative administered activity was 28.2 (7.3-29.9) GBq. Lymphopenia/lymphocyte count decreased and headache were the most common adverse events (AEs) during Cycle 1 (each 4/11 [36%]). Cycle 1 Grade ≥ 3 AEs occurred in 4/11 patients (36%). During the treatment period, the most common AE was lymphopenia/lymphocyte count decreased (7/11 [64%]; Grade ≥ 3, 5/11 [45%]). No clinically meaningful impacts on safety biomarkers nor any treatment-related nephrotoxicities were observed. Projected median (range) cumulative absorbed doses (four administrations) were 21 (14-40) Gy in kidneys and 0.76 (0.55-1.0) Gy in bone marrow (using blood data). Dosimetry values were predicted to be within safety thresholds for adolescents and adults; pharmacokinetics were comparable in both populations.

CONCLUSION

No new safety signals attributable to 177Lu-DOTATATE were identified in adolescents with GEP-NET or PPGL versus adults with GEP-NET. Long-term follow-up is ongoing.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT04711135. Registered 15 January 2021.

Patients, parents and professional perspectives on molecular radiotherapy for neuroblastoma and paediatric neuroendocrine cancers

Treatment with radioactive drugs (molecular radiotherapy, MRT) is an option for selected children with neuroblastoma and neuroendocrine cancers. As few hospitals are appropriately equipped and staffed to provide paediatric MRT, many families have to travel long distances from home for prolonged periods. To improve professional understanding of the challenges faced by children receiving these treatments and their parents, and to help them appreciate the difficulties faced by professionals in delivering complex treatments, a meeting bringing together parents, patients and professionals was held. Ten people (five parents of children with neuroblastoma, two parents of children with neuroendocrine cancers, two adults who had received treatment for neuroendocrine cancers in childhood and one adult treated for neuroblastoma) gave personal perspectives of treatment with MRT. Three professionals from different disciplines involved with this treatment and research to improve its results gave their views on the administration of MRT, and how treatment outcomes might be improved. Fifteen people, including parents and professionals, contributed to the general discussion. Following the meeting, a questionnaire was circulated to those attending to capture their overall views, and any reflections they may have had after the meeting. Whilst many positive comments and compliments were received, this report focuses on the reported challenges and difficulties. The event is an example of meaningful Patient and Public Involvement and Engagement and has resulted in development of better information resources, strategies to mitigate inconveniences experienced and a standing group of advocates to advise on research design and acceptability.

Theranostics for Neuroblastoma: Making Molecular Radiotherapy Work Better

Despite improvements in neuroblastoma treatment, survival figures lag behind those of many other childhood malignancies. New treatments, and better use of existing treatments, are essential to reduce mortality. Neuroblastoma expresses several molecular targets for radionuclide imaging and therapy, of which the most widely exploited is the norepinephrine transporter. [123I]metaiodobenzylguanidine (MIBG) imaging and [131I]MIBG treatment, which target this physiologic pathway, have been in clinical practice for 40 y. Although therapy outcomes have been favorable, [131I]MIBG use has not yet been optimized. Somatostatin receptors and the disialoganglioside are alternative targets, but their use remains experimental. The charity Children's Cancer Research Fund organized a workshop bringing together a broad range of scientists including radiochemists, radiobiologists, radiation physicists, clinical researchers including pediatric oncologists and nuclear medicine physicians, and patient advocates from the United Kingdom, United States, and continental Europe to share their experiences with molecular imaging and radiotherapy of neuroblastoma and discuss potential ways of improving treatment outcomes and access. These include development of alternative vectors targeting somatostatin receptors and disialoganglioside, isotopes such as α-particle and Auger electron emitters with different radiation characteristics, and combinations with external-beam radiotherapy, immunotherapy, and DNA damage repair inhibitors. Barriers to progress discussed included the unpredictable radioisotope supply, production of novel radiopharmaceuticals, lack of data regarding which are the best combination therapies, and insufficient clinical facilities. The aim was to stimulate the development and assessment of more effective treatments.

Central Nervous System Tumor-Embryonal Tumors Type With Neuroendocrine Differentiation

ABSTRACT

The central nervous system (CNS) tumor with embryonal tumors type is a rare type of CNS tumor with lack of unifying genetic alterations or diagnostic markers. The CNS tumor-embryonal tumors (CETs) have limited therapeutic options with high probability of adverse events associated with conventional treatment. Identification of somatostatin receptor expression and/or prostate-specific membrane antigen expression in CET patients by using PET/CT imaging may be helpful for deciding therapeutic approaches in these patients as theranostics. We present a 56-year-old woman who complained of headache, diminution of vision, and diagnosed CET and demonstrated high SSTR expression on PET/CT imaging, indicating peptide receptor radionuclide therapy could be effective therapeutic option in this case.

GD2-targeted theranostics of neuroblastoma with [64Cu]Cu/[177Lu]Lu-hu3F8

PURPOSE

Neuroblastoma (NB) is a malignant embryonic tumour with poor prognosis and high mortality rate. The antigen gisialoganglioside (GD2), which is highly expressed on the surface of NB cells, is an effective target for therapy. This study aims to evaluate the GD2 expression with [64Cu]Cu-NOTA-hu3F8 positron emission tomography (PET) imaging and explore the radioimmunotherapy (RIT) effect of [177Lu]Lu-DOTA-hu3F8 in NB tumour models.

METHODS

The in vitro validation of the binding ability of anti-GD2 humanised monoclonal antibody (hu3F8) to GD2 was achieved via flow cytometry, cell immunofluorescence, and cell uptake test. Hu3F8 were conjugated with p-SCN-Bn-NOTA (NOTA) and p-SCN-Bn-DOTA (DOTA) for 64Cu- and 177Lu- radiolabelling. PET imaging and RIT studies were conducted using [64Cu]Cu-NOTA-hu3F8 and [177Lu]Lu-DOTA-hu3F8 in subcutaneous NB tumour models.

RESULTS

The Institute for Medical Research-32 (IMR32) cell line exhibited a specific binding ability of hu3F8. PET imaging demonstrated a specific accumulation of [64Cu]Cu-NOTA-hu3F8 in IMR32 tumour models, with a maximum tumour uptake of 23.73 ± 2.29%ID/g (n = 3) at 72 h post-injection (p.i.), outperforming other groups significantly (P < 0.001). The high dose [177Lu]Lu-DOTA-hu3F8 group (11.1MBq) showed the most potent tumour suppression, with a standardised tumour volume of about 20.47 ± 6.32% at 30 days p.i., significantly smaller than other groups (n = 5, P < 0.05).

CONCLUSION

This study demonstrated that 64Cu-/177Lu- labelled hu3F8 could noninvasively evaluate the GD2 expression and effectively inhibit tumour growth in NB tumour models. The excellent therapeutic efficacy of [177Lu]Lu-DOTA-hu3F8 may be helpful for the clinical translation of this GD2-targeted theranostics approach in GD2-positive tumours.

PET/CT imaging of differentiated and medullary thyroid carcinoma using the novel SSTR-targeting peptide [18F]SiTATE - first clinical experiences

PURPOSE

The novel 18F-labeled somatostatin receptor (SSTR)-directed radiotracer [18F]SiTATE demonstrated promising results for the imaging of various SSTR-expressing tumor types. Although thyroid carcinomas (TC) express SSTR, data on [18F]SiTATE PET/CT imaging in TC are lacking. This study explores the use of [18F]SiTATE PET/CT in a patient cohort with histologically proven TC.

METHODS

As part of a prospective observational study at a single tertiary cancer center, 21 patients with TC (10 medullary (MTC) and 11 differentiated (DTC)) who underwent at least one [18F]SiTATE PET/CT were included (37 scans in total). Mean SUVmax and SUVmean of tumoral lesions, mean total-tumor-volume (TTV), and whole-body (WB)-SUVmax and WB-SUVmean on PET with their standard deviations (SDs) were determined. PET parameters were correlated to clinical parameters including tumor marker levels (thyroglobulin for DTC, calcitonin for MTC).

RESULTS

89 lesions were included in the analysis. Metastases were localized in the bone, lymph nodes, lung, soft tissue, and thyroid bed. Osseous (31 lesions; SUVmax 8.6 ± 8.0; SUVmean 5.8 ± 5.4) and nodal (37 lesions; SUVmax 8.7 ± 7.8; SUVmean 5.7 ± 5.4) metastases showed the highest uptake. The MTC disease burden on PET significantly correlated with the calcitonin tumor marker level (e.g., TTV: r = 0.771, r2 = 0.594, p = 0.002). For DTC, no such correlation was present.

CONCLUSION

Our data demonstrate high feasibility of [18F]SiTATE PET/CT in a small cohort of patients with MTC and DTC. The use of [18F]SiTATE may overcome logistical disadvantages of 68Ga-based tracers and facilitate SSTR-targeted PET/CT imaging of thyroid carcinoma.

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.

p53 stabilisation potentiates [177Lu]Lu-DOTATATE treatment in neuroblastoma xenografts

PURPOSE

Molecular radiotherapy is a treatment modality that is highly suitable for targeting micrometastases and [177Lu]Lu-DOTATATE is currently being explored as a potential novel treatment option for high-risk neuroblastoma. p53 is a key player in the proapoptotic signalling in response to radiation-induced DNA damage and is therefore a potential target for radiosensitisation.

METHODS

This study investigated the use of the p53 stabilising peptide VIP116 and [177Lu]Lu-DOTATATE, either alone or in combination, for treatment of neuroblastoma tumour xenografts in mice. Initially, the uptake of [177Lu]Lu-DOTATATE in the tumours was confirmed, and the efficacy of VIP116 as a monotherapy was evaluated. Subsequently, mice with neuroblastoma tumour xenografts were treated with placebo, VIP116, [177Lu]Lu-DOTATATE or a combination of both agents.

RESULTS

The results demonstrated that monotherapy with either VIP116 or [177Lu]Lu-DOTATATE significantly prolonged median survival compared to the placebo group (90 and 96.5 days vs. 50.5 days, respectively). Notably, the combination treatment further improved median survival to over 120 days. Furthermore, the combination group exhibited the highest percentage of complete remission, corresponding to a twofold increase compared to the placebo group. Importantly, none of the treatments induced significant nephrotoxicity. Additionally, the therapies affected various molecular targets involved in critical processes such as apoptosis, hypoxia and angiogenesis.

CONCLUSION

In conclusion, the combination of VIP116 and [177Lu]Lu-DOTATATE presents a promising novel treatment approach for neuroblastoma. These findings hold potential to advance research efforts towards a potential cure for this vulnerable patient population.

Clinical perspectives on dosimetry in molecular radiotherapy

Molecular radiotherapy is the use of systemically administered unsealed radioactive sources to treat cancer. Theragnostics is the term used to describe paired radiopharmaceuticals localising to a specific target, one optimised for imaging, the other for therapy. For many decades, molecular radiotherapy has developed empirically. Standard administered activity schedules have been used without the prior estimation of the resulting tumour radiation absorbed dose by theragnostic imaging, or its subsequent measurement by serial scanning. This pragmatic approach has benefited many patients, however others who should have benefited have failed to do so as the radiation absorbed dose in the tumour was suboptimal. The accurate prediction and measurement of tumour and organ at risk radiation absorbed doses allows treatment to be personalised, and offers the prospect of improved clinical outcomes. To deliver this for all molecular radiotherapy patients would require not only a significant financial investment in equipment and skilled personnel, but also a change in attitude of those who believe that simple - or simplistic - schedules are easier to deliver, and that accurate dosimetry is too much trouble. Further clinical studies are required to demonstrate beyond doubt that the advantages of individualised treatment planning outweigh the inconvenience, and that the expense is justified by enhanced results.

Case report: Peptide receptor radioligand therapy in metastatic pediatric neuroendocrine tumors

Neuroendocrine tumors (NETs) are not commonly diagnosed in children. Metastatic NETs tend to have poor outcomes, and this is seen in adult and pediatric populations. The role of somatostatin receptor imaging using [68Ga]Ga-DOTA-TATE for imaging and peptide receptor radionuclide therapy (PRRT) with [177Lu]Lu-DOTA-TATE in children is currently not well established. The guidelines for treating pediatric neuroendocrine tumors are still lacking. Extensive trials have been conducted in adult patients and have demonstrated improved survival in metastatic NETs with PRRT using [177Lu]Lu-DOTA-TATE. We present two pediatric patients with metastatic NETs who were imaged with [68Ga]Ga-DOTA-TATE PET/CT and treated with [177Lu]Lu-DOTA-TATE therapy.

Pediatric Neuroendocrine Neoplasms: Rare Malignancies with Incredible Variability

Neuroendocrine neoplasms (NENs) encompass a variety of neuroendocrine tumors (NETs) and neuroendocrine carcinomas (NECs) which can arise anywhere in the body. While relatively rare in the pediatric population, the incidence of NENs has increased in the past few decades. These neoplasms can be devastating if not diagnosed and treated early, however, symptoms are variable and can be indolent for many years. There is a reported median of 10 years from the appearance of the first symptoms to time of diagnosis. Considering some of these neoplasms have a mortality rate as high as 90%, it is crucial healthcare providers are aware of NENs and remain vigilant. With better provider education and easily accessible resources for information about these neoplasms, awareness can be improved leading to earlier disease recognition and diagnosis. This manuscript aims to provide an overview of both the most common NENs as well as the rarer NENs with high lethality in the pediatric population. This review provides up to date evidence and recommendations, encompassing recent changes in classification and advances in treatment modalities, including recently completed and ongoing clinical trials.

Advancing therapy for neuroblastoma

Neuroblastomas are tumours of sympathetic origin, with a heterogeneous clinical course ranging from localized or spontaneously regressing to widely metastatic disease. Neuroblastomas recapitulate many of the features of sympathoadrenal development, which have been directly targeted to improve the survival outcomes in patients with high-risk disease. Over the past few decades, improvements in the 5-year survival of patients with metastatic neuroblastomas, from <20% to >50%, have resulted from clinical trials incorporating high-dose chemotherapy with autologous stem cell transplantation, differentiating agents and immunotherapy with anti-GD2 monoclonal antibodies. The next generation of trials are designed to improve the initial response rates in patients with high-risk neuroblastomas via the addition of immunotherapies, targeted therapies (such as ALK inhibitors) and radiopharmaceuticals to standard induction regimens. Other trials are focused on testing precision medicine strategies for patients with relapsed and/or refractory disease, enhancing the antitumour immune response and improving the effectiveness of maintenance regimens, in order to prolong disease remission. In this Review, we describe advances in delineating the pathogenesis of neuroblastoma and in identifying the drivers of high-risk disease. We then discuss how this knowledge has informed improvements in risk stratification, risk-adapted therapy and the development of novel therapies.

Clinical parameters combined with radiomics features of PET/CT can predict recurrence in patients with high-risk pediatric neuroblastoma

Background

This retrospective study aimed to develop and validate a combined model based [¹⁸F]FDG PET/CT radiomics and clinical parameters for predicting recurrence in high-risk pediatric neuroblastoma patients.

Methods

Eighty-four high-risk neuroblastoma patients were retrospectively enrolled and divided into training and test sets according to the ratio of 3:2. [¹⁸F]FDG PET/CT images of the tumor were segmented by 3D Slicer software and the radiomics features were extracted. The effective features were selected by the least absolute shrinkage and selection operator to construct the radiomics score (Rad_score). And the radiomics model (R_model) was constructed based on Rad_score for prediction of recurrence. Then, univariate and multivariate analyses were used to screen out the independent clinical risk parameters and construct the clinical model (C_model). A combined model (RC_model) was developed based on the Rad_score and independent clinical risk parameters and presented as radiomics nomogram. The performance of the above three models was assessed by the area under the receiver operating characteristic curve (AUC) and decision curve analysis (DCA).

Results

Seven radiomics features were selected for building the R_model. The AUCs of the C_model in training and test sets were 0.744 (95% confidence interval [CI], 0.595–0.874) and 0.750 (95% CI, 0.577–0.904), respectively. The R_model yielded AUCs of 0.813 (95% CI, 0.685–0.916) and 0.869 (95% CI, 0.715–0.985) in the training and test sets, respectively. The RC_model demonstrated the largest AUCs of 0.889 (95% CI, 0.794–0.963) and 0.892 (95% CI, 0.758–0.992) in the training and test sets, respectively. DCA demonstrated that RC_model added more net benefits than either the C_model or the R_model for predicting recurrence in high-risk pediatric neuroblastoma.

Conclusions

The combined model performed well for predicting recurrence in high-risk pediatric neuroblastoma, which can facilitate disease follow-up and management in clinical practice.

Impact of cyclic changes in pharmacokinetics and absorbed dose in pediatric neuroblastoma patients receiving [177Lu]Lu-DOTATATE

PURPOSE

Recent reports personalizing the administered activity (AA) of each cycle of peptide receptor radionuclide therapy based on the predicted absorbed dose (AD) to the kidneys (dose-limiting organ) have been promising. Assuming identical renal pharmacokinetics for each cycle is pragmatic, however it may lead to over- or under-estimation of the optimal AA. Here, we investigate the influence that earlier cycles of [177Lu]Lu-DOTATATE had on the biokinetics and AD of subsequent cycles in a recent clinical trial that evaluated the safety and activity of [177Lu]Lu-DOTATATE in pediatric neuroblastoma (NBL). We investigated whether predictions based on an assumption of unchanging AD per unit AA (Gy/GBq) prove robust to cyclical changes in biokinetics.

METHODS

A simulation study, based on dosimetry data from six children with NBL who received four-cycles of [177Lu]Lu-DOTATATE in the LuDO trial (ISRCTN98918118), was performed to explore the effect of variable biokinetics on AD. In the LuDO trial, AA was adapted to the patient's weight and SPECT/CT-based dosimetry was performed for the kidneys and tumour after each cycle. The largest tumour mass was selected for dosimetric analysis in each case.

RESULTS

The median tumour AD per cycle was found to decrease from 15.6 Gy (range 8.12-26.4) in cycle 1 to 11.4 Gy (range 9.67-28.8), 11.3 Gy (range 2.73-32.9) and 4.3 Gy (range 0.72-20.1) in cycles 2, 3 and 4, respectively. By the fourth cycle, the median of the ratios of the delivered AD (ADD) and the predicted (or "expected") AD (ADE) (which was based on an assumption of stable biokinetics from the first cycle onwards) were 0.16 (range 0.02-0.92, p = 0.013) for the tumour and 1.08 (range 0.84-1.76, p > 0.05) for kidney. None of the patients had an objective response at 1 month follow up.

CONCLUSION

This study demonstrates variability in Gy/GBq and tumour AD per cycle in children receiving four administrations of [177Lu]Lu-DOTATATE treatment for NBL. NBL is deemed a radiation sensitive tumour; therefore, dose-adaptive treatment planning schemes may be appropriate for some patients to compensate for decreasing tumour uptake as treatment progresses. Trial registration ISRCTN ISRCTN98918118. Registered 20 December 2013 (retrospectively registered).

A Phase II Trial of a Personalized, Dose-Intense Administration Schedule of 177Lutetium-DOTATATE in Children With Primary Refractory or Relapsed High-Risk Neuroblastoma-LuDO-N

Background

Half the children with high-risk neuroblastoma die with widespread metastases. Molecular radiotherapy is an attractive systemic treatment for this relatively radiosensitive tumor. 131I-mIBG is the most widely used form in current use, but is not universally effective. Clinical trials of 177Lutetium DOTATATE have so far had disappointing results, possibly because the administered activity was too low, and the courses were spread over too long a period of time, for a rapidly proliferating tumor. We have devised an alternative administration schedule to overcome these limitations. This involves two high-activity administrations of single agent 177Lu-DOTATATE given 2 weeks apart, prescribed as a personalized whole body radiation absorbed dose, rather than a fixed administered activity. "A phase II trial of 177Lutetium-DOTATATE in children with primary refractory or relapsed high-risk neuroblastoma - LuDO-N" (EudraCT No: 2020-004445-36, ClinicalTrials.gov Identifier: NCT04903899) evaluates this new dosing schedule.

Methods

The LuDO-N trial is a phase II, open label, multi-center, single arm, two stage design clinical trial. Children aged 18 months to 18 years are eligible. The trial is conducted by the Nordic Society for Pediatric Hematology and Oncology (NOPHO) and it has been endorsed by SIOPEN (https://www.siopen.net). The Karolinska University Hospital, is the sponsor of the LuDO-N trial, which is conducted in collaboration with Advanced Accelerator Applications, a Novartis company. All Scandinavian countries, Lithuania and the Netherlands participate in the trial and the UK has voiced an interest in joining in 2022.

Results

The pediatric use of the Investigational Medicinal Product (IMP) 177Lu-DOTATATE, as well as non-IMPs SomaKit TOC® (68Ga-DOTATOC) and LysaKare® amino acid solution for renal protection, have been approved for pediatric use, within the LuDO-N Trial by the European Medicines Agency (EMA). The trial is currently recruiting. Recruitment is estimated to be finalized within 3-5 years.

Discussion

In this paper we present the protocol of the LuDO-N Trial. The rationale and design of the trial are discussed in relation to other ongoing, or planned trials with similar objectives. Further, we discuss the rapid development of targeted radiopharmaceutical therapy and the future perspectives for developing novel therapies for high-risk neuroblastoma and other pediatric solid tumors.

Treatment of Neuroendocrine Neoplasms with Radiolabeled Peptides-Where Are We Now

Peptide receptor radionuclide therapy (PRRT) has been one of the most successful and exciting examples of theranostics in nuclear medicine in recent decades and is now firmly embedded in many treatment algorithms for unresectable or metastatic neuroendocrine neoplasms (NENs) worldwide. It is widely considered to be an effective treatment for well- or moderately differentiated neoplasms, which express high levels of somatostatin receptors that can be selectively targeted. This review article outlines the scientific basis of PRRT in treatment of NENs and describes its discovery dating back to the early 1990s. Early treatments utilizing Indium-111, a γ-emitter, showed promise in reduction in tumor size and improvement in biochemistry, but were also met with high radiation doses and myelotoxic and nephrotoxic effects. Subsequently, stable conjugation of DOTA-peptides with β-emitting radionuclides, such as Yttrium-90 and Lutetium-177, served as a breakthrough for PRRT and studies highlighted their potential in eliciting progression-free survival and quality of life benefits. This article will also elaborate on the key trials which paved the way for its approval and will discuss therapeutic considerations, such as patient selection and administration technique, to optimize its use.

Renal protection during 177lutetium DOTATATE molecular radiotherapy in children: a proposal for safe amino acid infusional volume during peptide receptor radionuclide therapy

Peptide receptor radionuclide therapy (PRRT) using radiolabelled somatostatin analogues such as 177-lutetium DOTATATE is an effective treatment modality for neuroendocrine tumours, paragangliomas, and neuroblastomas. However, renal and haematopoietic toxicities are the major limitations of this therapeutic approach. The renal toxicity of PRRT is mediated by renal proximal tubular reabsorption and interstitial retention of the radiolabelled peptides resulting in excessive renal irradiation that can be dose-limiting. To protect the kidneys from PRRT-induced radiation nephropathy, basic amino acids are infused during PRRT as they competitively bind to the proximal tubular cells and prevent uptake of the radionuclide. In adults, 1 L of a basic amino acid solution consisting of arginine and lysine is infused over 4 h commencing 30 min prior to PRRT. However, this volume of amino acids infused over 4 h is excessive in small children and can result in hemodynamic overload. This is all the more relevant in paediatric oncology, as many of the children may have been heavily pretreated and so may have treatment-related renal and or cardiac impairment. We have therefore developed the following guidelines for safe paediatric dosing of renal protective amino acid infusions during PRRT. Our recommendations have been made taking into consideration the renal physiology in small children and the principles of safe fluid management in children.

p53-Mediated Radiosensitization of 177Lu-DOTATATE in Neuroblastoma Tumor Spheroids

p53 is involved in DNA damage response and is an exciting target for radiosensitization in cancer. Targeted radionuclide therapy against somatostatin receptors with 177Lu-DOTATATE is currently being explored as a treatment for neuroblastoma. The aim of this study was to investigate the novel p53-stabilizing peptide VIP116 in neuroblastoma, both as monotherapy and together with 177Lu-DOTATATE. Five neuroblastoma cell lines, including two patient-derived xenograft (PDX) lines, were characterized in monolayer cultures. Four out of five were positive for 177Lu-DOTATATE uptake. IC50 values after VIP116 treatments correlated with p53 status, ranging between 2.8-238.2 μM. IMR-32 and PDX lines LU-NB-1 and LU-NB-2 were then cultured as multicellular tumor spheroids and treated with 177Lu-DOTATATE and/or VIP116. Spheroid growth was inhibited in all spheroid models for all treatment modalities. The most pronounced effects were observed for combination treatments, mediating synergistic effects in the IMR-32 model. VIP116 and combination treatment increased p53 levels with subsequent induction of p21, Bax and cleaved caspase 3. Combination treatment resulted in a 14-fold and 1.6-fold induction of MDM2 in LU-NB-2 and IMR-32 spheroids, respectively. This, together with differential MYCN signaling, may explain the varying degree of synergy. In conclusion, VIP116 inhibited neuroblastoma cell growth, potentiated 177Lu-DOTATATE treatment and could, therefore, be a feasible treatment option for neuroblastoma.

Neuroblastoma xenograft models demonstrate the therapeutic potential of 177Lu-octreotate

BACKGROUND

Neuroblastoma (NB) is one of the most frequently diagnosed tumors in infants. NB is a neuroendocrine tumor type with various characteristics and features, and with diverse outcome. The most malignant NBs have a 5-year survival rate of only 40-50%, indicating the need for novel and improved treatment options. 177Lu-octreotate is routinely administered for treatment of neuroendocrine tumors overexpressing somatostatin receptors (SSTR). The aim of this study was to examine the biodistribution of 177Lu-octreotate in mice bearing aggressive human NB cell lines, in order to evaluate the potential usefulness of 177Lu-octreotate for treatment of NB.

METHODS

BALB/c nude mice bearing CLB-BAR, CLB-GE or IMR-32 tumor xenografts (n = 5-7/group) were i.v. injected with 0.15 MBq, 1.5 MBq or 15 MBq 177Lu-octreotate and sacrificed 1 h, 24 h, 48 h and 168 h after administration. The radioactivity concentration was determined for collected tissue samples, tumor-to-normal-tissue activity concentration ratios (T/N) and mean absorbed dose for each tissue were calculated. Immunohistochemical (IHC) staining for SSTR1-5, and Ki67 were carried out for tumor xenografts from the three cell lines.

RESULTS

High 177Lu concentration levels and T/N values were observed in all NB tumors, with the highest for CLB-GE tumor xenografts (72%IA/g 24 h p.i.; 1.5 MBq 177Lu-octreotate). The mean absorbed dose to the tumor was 6.8 Gy, 54 Gy and 29 Gy for CLB-BAR, CLB-GE and IMR-32, respectively, p.i. of 15 MBq 177Lu-octreotate. Receptor saturation was clearly observed in CLB-BAR, resulting in higher concentration levels in the tumor when lower activity levels where administered. IHC staining demonstrated highest expression of SSTR2 in CLB-GE, followed by CLB-BAR and IMR-32.

CONCLUSION

T/N values for all three human NB tumor xenograft types investigated were high relative to previously investigated neuroendocrine tumor types. The results indicate a clear potential of 177Lu-octreotate as a therapeutic alternative for metastatic NB.

68Ga-DOTATATE and 123I-mIBG as imaging biomarkers of disease localisation in metastatic neuroblastoma: implications for molecular radiotherapy

PURPOSE

Iodine-131-labelled meta-iodobenzylguanidine (I-mIBG) and lutetium-177-labelled DOTATATE (Lu-DOTATATE) are used for molecular radiotherapy of metastatic neuroblastoma. These are taken up by the noradrenaline transporter (NAT) and the somatostatin receptor subtype 2 (SSTR-2), respectively. Scintigraphy of iodine-123-labelled meta-iodobenzylguanidine (I-mIBG) and gallium-68 DOTATATE (Ga-DOTATATE) PET are used to select patients for therapy. These demonstrate the extent and location of tumour, and avidity of uptake by cells expressing NAT and SSTR-2, respectively. This study compared the similarities and differences in the anatomical distribution of these two imaging biomarkers in an unselected series of patients with metastatic neuroblastoma undergoing assessment for molecular radiotherapy.

METHODS

Paired whole-body planar I-mIBG views and Ga-DOTATATE maximum intensity projection PET scans of metastatic neuroblastoma patients were visually compared. The disease extent was assessed by a semiquantitative scoring method.

RESULTS

Paired scans from 42 patients were reviewed. Ga-DOTATATE scans were positive in all patients, I-mIBG scans were negative in two. In two patients, there was a mismatch, with some lesions identified only on the I-mIBG scan, and others visible only on the Ga-DOTATATE scan.

CONCLUSION

Ga-DOTATATE and I-mIBG scans yield complementary information. For a more comprehensive assessment, consideration could be given to the use of both I-mIBG and Ga-DOTATATE imaging scans. Because of the heterogeneity of distribution of molecular targets revealed by these techniques, a combination of both I-mIBG and Lu-DOTATATE molecular radiotherapy may possibly be more effective than either alone.

Theranostics in Neuroblastoma

Theranostics combines diagnosis and targeted therapy, achieved by the use of the same or similar molecules labeled with different radiopharmaceuticals or identical with different dosages. One of the best examples is the use of metaiodobenzylguanidine (MIBG). In the management of neuroblastoma-the most common extracranial solid tumor in children. MIBG has utility not only for diagnosis, risk-stratification, and response monitoring but also for cancer therapy, particularly in the setting of relapsed/refractory disease. Improved techniques and new emerging radiopharmaceuticals likely will strengthen the role of nuclear medicine in the management of neuroblastoma.

Peptide receptor radionuclide therapy for treatment of metastatic neuroendocrine tumors in children

Neuroendocrine tumors (NETs) of the pancreas and midgut are extremely rare in children, and patients presenting with metastatic disease have poor survival. Given this rarity, treatments are extrapolated from guidelines for adults with NET. Recent clinical trials in adults with NETs have shown that the addition of peptide receptor radionuclide therapy (PRRT) with ¹⁷⁷ Lu-DOTATATE resulted in a disease control rate of nearly 80%, with minimal side effects. We report our experience using ¹⁷⁷ Lu-DOTATATE to treat two pediatric patients with metastatic NET.

Feasibility and Therapeutic Potential of Combined Peptide Receptor Radionuclide Therapy With Intensive Chemotherapy for Pediatric Patients With Relapsed or Refractory Metastatic Neuroblastoma

BACKGROUND

Recent evidence has demonstrated high expression of somatostatin receptors in neuroblastoma (NB) cells. Because of this, we endeavored to evaluate the diagnostic performance and clinical efficacy of 68Ga-DOTATATE PET/CT and peptide receptor radionuclide therapy (PRRT) using 177Lu-DOTATATE combined with chemotherapy in pediatric NB patients.

PATIENTS AND METHODS

In total, 14 pediatric patients with histopathologically confirmed NB underwent 68Ga-DOTATATE PET/CT. Among them, the patients who were refractory or relapsed after therapy with 131I-MIBG and had intensive uptake of 68Ga-DOTATATE were referred for PRRT using 177Lu-DOTATATE. Treatment response based on follow-up imaging was classified into complete response, partial response, stable disease, and progressive disease. After each cycle of PRRT, laboratory tests were performed for evaluation of hematological, renal, and hepatic toxicities. The CTCAE (Common Terminology Criteria for Adverse Events; version 4.03) was used for grading adverse event. Curie score and International Society of Pediatric Oncology Europe Neuroblastoma score were used for semiquantitative analysis of scans of patients who underwent PRRT. In addition, overall survival was calculated as the time interval between the date of the first cycle and the end of follow-up or death.

RESULTS

Overall, 14 refractory NB children including 7 boys and 7 girls with a median age of 5.5 years (ranged from 4 to 9) underwent 68Ga-DOTATATE PET/CT. PET/CT was positive in 10/14 patients (71.4%), and the median number of detected lesions in positive patients was 2 (range, 1-13). Of 14 patients, 5 patients underwent PRRT, including 3 boys and 2 girls. A total of 19 PRRT cycles and 66.4 GBq 177Lu-DOTATATE were given. Among these 5 patients, 2 showed an initial complete response, which relapsed a few months later, 1 showed a partial response, and 2 showed progressive disease. According to the Kaplan-Meier test, the overall survival was estimated at 14.5 months (95% confidence interval, 8.9-20.1). In evaluation of PRRT-related toxicity according to the CTCAE, 4 patients showed grade 1, and 1 showed grade 2 leukopenia. Two patients showed grade 1, and 2 others showed grade 2 anemia. Two patients showed grade 1, and 3 patients showed grade 2 thrombocytopenia. Serum creatinine in 1 patient increased to grade 1.

CONCLUSIONS

Combination of 177Lu-DOTATATE with chemotherapeutic agents might achieve worthwhile responses with low toxicity, encouraging survival in NB patients who have relapsed or are refractory to conventional therapy, including 131I-MIBG therapy. Imaging with 68Ga-DOTATATE PET/CT in such patients has a relatively high detection efficacy, demonstrating its potential use as an alternative imaging tool to conventional modalities such as 123I/131I-MIBG. However, further well-designed trials are highly warranted.

Nuclear Medicine Imaging in Neuroblastoma: Current Status and New Developments

Neuroblastoma is the most common extracranial solid malignancy in children. At diagnosis, approximately 50% of patients present with metastatic disease. These patients are at high risk for refractory or recurrent disease, which conveys a very poor prognosis. During the past decades, nuclear medicine has been essential for the staging and response assessment of neuroblastoma. Currently, the standard nuclear imaging technique is meta-[¹²³I]iodobenzylguanidine ([¹²³I]mIBG) whole-body scintigraphy, usually combined with single-photon emission computed tomography with computed tomography (SPECT-CT). Nevertheless, 10% of neuroblastomas are mIBG non-avid and [¹²³I]mIBG imaging has relatively low spatial resolution, resulting in limited sensitivity for smaller lesions. More accurate methods to assess full disease extent are needed in order to optimize treatment strategies. Advances in nuclear medicine have led to the introduction of radiotracers compatible for positron emission tomography (PET) imaging in neuroblastoma, such as [¹²⁴I]mIBG, [¹⁸F]mFBG, [¹⁸F]FDG, [⁶⁸Ga]Ga-DOTA peptides, [¹⁸F]F-DOPA, and [¹¹C]mHED. PET has multiple advantages over SPECT, including a superior resolution and whole-body tomographic range. This article reviews the use, characteristics, diagnostic accuracy, advantages, and limitations of current and new tracers for nuclear medicine imaging in neuroblastoma.

Detection and therapy of neuroblastoma minimal residual disease using [64/67Cu]Cu-SARTATE in a preclinical model of hepatic metastases

Background

A major challenge to the long-term success of neuroblastoma therapy is widespread metastases that survive initial therapy as minimal residual disease (MRD). The SSTR2 receptor is expressed by most neuroblastoma tumors making it an attractive target for molecularly targeted radionuclide therapy. SARTATE consists of octreotate, which targets the SSTR2 receptor, conjugated to MeCOSar, a bifunctional chelator with high affinity for copper. Cu-SARTATE offers the potential to both detect and treat neuroblastoma MRD by using [⁶⁴Cu]Cu-SARTATE to detect and monitor the disease and [⁶⁷Cu]Cu-SARTATE as the companion therapeutic agent. In the present study, we tested this theranostic pair in a preclinical model of neuroblastoma MRD. An intrahepatic model of metastatic neuroblastoma was established using IMR32 cells in nude mice. The biodistribution of [⁶⁴Cu]Cu-SARTATE was measured using small-animal PET and ex vivo tissue analysis. Survival studies were carried out using the same model: mice (6–8 mice/group) were given single doses of saline, or 9.25 MBq (250 µCi), or 18.5 MBq (500 µCi) of [⁶⁷Cu]Cu-SARTATE at either 2 or 4 weeks after tumor cell inoculation.

Results

PET imaging and ex vivo biodistribution confirmed tumor uptake of [⁶⁴Cu]Cu-SARTATE and rapid clearance from other tissues. The major clearance tissues were the kidneys (15.6 ± 5.8% IA/g at 24 h post-injection, 11.5 ± 2.8% IA/g at 48 h, n = 3/4). Autoradiography and histological analysis confirmed [⁶⁴Cu]Cu-SARTATE uptake in viable, SSTR2-positive tumor regions with mean tumor uptakes of 14.1–25.0% IA/g at 24 h. [⁶⁷Cu]Cu-SARTATE therapy was effective when started 2 weeks after tumor cell inoculation, extending survival by an average of 13 days (30%) compared with the untreated group (mean survival of control group 43.0 ± 8.1 days vs. 55.6 ± 9.1 days for the treated group; p = 0.012). No significant therapeutic effect was observed when [⁶⁷Cu]Cu-SARTATE was started 4 weeks after tumor cell inoculation, when the tumors would have been larger (control group 14.6 ± 8.5 days; 9.25 MBq group 9.5 ± 1.6 days; 18.5 MBq group 15.6 ± 4.1 days; p = 0.064).

Conclusions

Clinical experiences of peptide-receptor radionuclide therapy for metastatic disease have been encouraging. This study demonstrates the potential for a theranostic approach using [^64/67Cu]Cu-SARTATE for the detection and treatment of SSTR2-positive neuroblastoma MRD.

Paediatric Molecular Radiotherapy: Challenges and Opportunities

The common contemporary indications for paediatric molecular radiotherapy (pMRT) are differentiated thyroid cancer and neuroblastoma. It may also have value in neuroendocrine cancers, and it is being investigated in clinical trials for other diseases. pMRT is the prototypical biomarker-driven, precision therapy, with a unique mode of delivery and mechanism of action. It is safe and well tolerated, compared with other treatments. However, its full potential has not yet been achieved, and its wider use faces a number of challenges and obstacles. Paradoxically, the success of radioactive iodine as a curative treatment for metastatic thyroid cancer has led to a 'one size fits all' approach and limited academic enquiry into optimisation of the conventional treatment regimen, until very recently. Second, the specialised requirements for the delivery of pMRT are available in only a very limited number of centres. This limited capacity and geographical coverage results in reduced accessibility. With few enthusiastic advocates for this treatment modality, investment in research to improve treatments and broaden indications from both industry and national and charitable research funders has historically been suboptimal. Nonetheless, there is now an increasing interest in the opportunities offered by pMRT. Increased research funding has been allocated, and technical developments that will permit innovative approaches in pMRT are available for exploration. A new portfolio of clinical trials is being assembled. These studies should help to move at least some paediatric treatments from simply palliative use into potentially curative protocols. Therapeutic strategies require modification and optimisation to achieve this. The delivery should be personalised and tailored appropriately, with a comprehensive evaluation of tumour and organ-at-risk dosimetry, in alignment with the external beam model of radiotherapy. This article gives an overview of the current status of pMRT, indicating the barriers to progress and identifying ways in which these may be overcome.

Personalisation of Molecular Radiotherapy through Optimisation of Theragnostics

Molecular radiotherapy, or targeted radionuclide therapy, uses systemically administered drugs bearing a suitable radioactive isotope, typically a beta emitter. These are delivered via metabolic or other physiological pathways to cancer cells in greater concentrations than to normal tissues. The absorbed radiation dose in tumour deposits causes chromosomal damage and cell death. A partner radiopharmaceutical, most commonly the same vector labelled with a different radioactive atom, with emissions suitable for gamma camera or positron emission tomography imaging, is used to select patients for treatment and to assess response. The use of these pairs of radio-labelled drugs, one optimised for therapy, the other for diagnostic purposes, is referred to as theragnostics. Theragnostics is increasingly moving away from a fixed number of defined activity administrations, to a much more individualised or personalised approach, with the aim of improving treatment outcomes, and minimising toxicity. There is, however, still significant scope for further progress in that direction. The main tools for personalisation are the following: imaging biomarkers for better patient selection; predictive and post-therapy dosimetry to maximise the radiation dose to the tumour while keeping organs at risk within tolerance limits; imaging for assessment of treatment response; individualised decision making and communication about radiation protection, adjustments for toxicity, inpatient and outpatient care.