MIBG (metaiodobenzylguanidine) theranostics in pediatric and adult malignancies

Navigating the landscape of theranostics in nuclear medicine: current practice and future prospects

Theranostics refers to the combination of diagnostic biomarkers with therapeutic agents that share a specific target expressed by diseased cells and tissues. Nuclear medicine is an exciting component explored for its applicability in theranostic concepts in clinical and research investigations. Nuclear theranostics is based on the employment of radioactive compounds delivering ionizing radiation to diagnose and manage certain diseases employing binding with specifically expressed targets. In the realm of personalized medicine, nuclear theranostics stands as a beacon of potential, potentially revolutionizing disease management. Studies exploring the theranostic profile of radioactive compounds have been presented in this review along with a detailed explanation of radioactive compounds and their theranostic applicability in several diseases. It furnishes insights into their applicability across diverse diseases, elucidating the intricate interplay between these compounds and disease pathologies. Light is shed on the important milestones of nuclear theranostics beginning with radioiodine therapy in thyroid carcinomas, MIBG labelled with iodine in neuroblastoma, and several others. Our perspectives have been put forth regarding the most important theranostic agents along with emerging trends and prospects.

Reaching the target dose with one single 131 I-mIBG administration in high-risk neuroblastoma: The determinant impact of the primary tumour

BACKGROUND

131 I-metaiodobenzylguanidine (131 I-mIBG) effectiveness in children with metastasised neuroblastoma (NB) is linked to the effective dose absorbed by the target; a target of 4 Gy whole-body dose threshold has been proposed. Achieving this dose often requires administering 131 I-mIBG twice back-to-back, which may cause haematological toxicity. In this study, we tried identifying the factors predicting the achievement of 4 Gy whole-body dose with a single radiopharmaceutical administration.

MATERIALS AND METHODS

Children affected by metastatic NB and treated with a high 131 I-mIBG activity (>450 MBq (megabecquerel)/kg) were evaluated retrospectively. Kinetics measurements were carried out at multiple time points to estimate the whole-body dose, which was compared with clinical and activity-related parameters.

RESULTS

Seventeen children (12 females, median age 3 years, age range: 1.5-6.9 years) were included. Eleven of them still bore the primary tumour. The median whole-body dose was 2.88 Gy (range: 1.63-4.22 Gy). Children with a 'bulky' primary (>30 mL) received a higher whole-body dose than those with smaller or surgically removed primaries (3.42 ± 0.74 vs. 2.48 ± 0.65 Gy, respectively, p = .016). Conversely, the correlation between activity/kg and the whole-body dose was moderate (R: 0.42, p = .093). In the multivariate analysis, the volume of the primary tumour was the most relevant predictor of the whole-body dose (p = .002).

CONCLUSIONS

These data suggest that the presence of a bulky primary tumour can significantly prolong the 131 I-mIBG biological half-life, effectively increasing the absorbed whole-body dose. This information could be used to model the administered activity, allowing to attain the target dose without needing a two-step radiopharmaceutical administration.

Ligand-Enabled Copper-Mediated Radioiodination of Arenes

The discovery of a copper precatalyst that facilitates the key mechanistic steps of arene halodeboronation has allowed a step change in the synthesis of radioiodine-containing arenes. The active precatalyst [Cu(OAc)(phen)2]OAc was shown to perform room temperature radio-iododeboronation of aryl boronic acids with 1-2 mol % loadings and 10 min reaction times. These mild conditions enable particularly clean reactions, as demonstrated with the efficient preparation of the radiopharmaceutical and SPECT tracer, meta-iodobenzylguanidine (MIBG).

An audit of medullary thyroid carcinoma from a tertiary care hospital in northwest India

Introduction

Medullary thyroid carcinoma (MTC) is a rare thyroid malignancy originating from parafollicular C cells. It accounts for 5%-10% of all thyroid malignancies.

Methods

An ambispective analysis of pathologically proven MTC presented in a tertiary care hospital in northwest India was performed after considering demography, clinical manifestation, RET mutation status, management, and outcome as denominators.

Results

Among 2,735 thyroid malignancy cases who presented to our institute in the last 10 years (2012-2022), 78 (3%) had MTC with a mean age of presentation of 43 ± 11 years; 60% of them were female. The median duration of symptoms was 23 months (IQR 12-36 months). The most common presenting complaint was goiter with lymphadenopathy (80.8%). Among the atypical presentations, one each had ectopic Cushing's syndrome, hypertensive crisis in pregnancy due to pheochromocytoma, synchronous chondrosarcoma, and Von Hippel-Lindau disease spectrum. Median calcitonin and carcinoembryonic antigen (CEA) levels at presentation were 1,274 pg/mL (n = 64) and 149 ng/mL (n = 39), respectively. Twenty-two patients were germline RET mutation-positive, and they presented at a younger age. Majority of the patients presented with stage IV disease. Surgery was the primary modality of therapy. Twenty-nine patients received radiotherapy and 25 patients received tyrosine kinase inhibitors (TKIs). Nine patients received peptide receptor radiotherapy (PRRT) with Lu-177 with neoadjuvant capecitabine. Median progression-free survival (PFS) was 60 months. Patients without structurally and biochemically residual disease and stable disease after the first modality of therapy (Log-rank 11.4; p = 0.004) had a better PFS. Female patients (Log-rank: 9.5; p = 0.002) had a better PFS than male patients.

Conclusion

This study showed that MTC comprises 3% of thyroid malignancies with a female preponderance. RET mutation-positive patients had a younger age at presentation. Surgery was the first-line therapy. Radiotherapy, TKI, and PRRT were given as a part of second-line or third-line therapy due to persistent disease and/or disease recurrence. The median PFS was better in female patients and in patients who had no residual lesions and stable disease after the primary modality of therapy.

Biodistribution and radiation dosimetry of 124I-mIBG in adult patients with neural crest tumours and extrapolation to paediatric models

AIM

Positron emission tomography (PET) using 124I-mIBG has been established for imaging and pretherapeutic dosimetry. Here, we report the first systematic analysis of the biodistribution and radiation dosimetry of 124I-mIBG in patients with neural crest tumours and project the results to paediatric patient models.

METHODS

Adult patients with neural crest tumours who underwent sequential 124I-mIBG PET were included in this retrospective single-center analysis. PET data were acquired 4, 24, 48, and/or 120 h after administration of a mean of 43 MBq 124I-mIBG. Whole-body counting and blood sampling were performed at 2, 4, 24, 48 and 120 h after administration. Absorbed organ dose and effective dose coefficients were estimated in OLINDA/EXM 2.2 according to the MIRD formalism. Extrapolation to paediatric models was performed based on mass-fraction scaling of the organ-specific residence times. Biodistribution data for adults were also projected to 123I-mIBG and 131I-mIBG.

RESULTS

Twenty-one patients (11 females, 10 males) were evaluated. For adults, the organs exposed to the highest dose per unit administered activity were urinary bladder (1.54 ± 0.40 mGy/MBq), salivary glands (0.77 ± 0.28 mGy/MBq) and liver (0.65 ± 0.22 mGy/MBq). Mean effective dose coefficient for adults was 0.25 ± 0.04 mSv/MBq (male: 0.24 ± 0.03 mSv/MBq, female: 0.26 ± 0.06 mSv/MBq), and increased gradually to 0.29, 0.44, 0.69, 1.21, and 2.94 mSv/MBq for the 15-, 10-, 5-, 1-years-old, and newborn paediatric reference patients. Projected mean effective dose coefficients for 123I-mIBG and 131I-mIBG for adults were 0.014 ± 0.002 mSv/MBq and 0.18 ± 0.04 mSv/MBq, respectively.

CONCLUSION

PET-based derived radiation dosimetry data for 124I-mIBG from this study agreed well with historical projected data from ICRP 53. The effective dose coefficients presented here may aid in guidance for establishing weight-based activity administration protocols.

Cardiac 123I-Metaiodobenzylguanidine (MIBG) Scintigraphy in Parkinson's Disease: A Comprehensive Review

Cardiac sympathetic denervation, as documented on 123I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy, is relatively sensitive and specific for distinguishing Parkinson's disease (PD) from other neurodegenerative causes of parkinsonism. The present study aims to comprehensively review the literature regarding the use of cardiac MIBG in PD. MIBG is an analog to norepinephrine. They share the same uptake, storage, and release mechanisms. An abnormal result in the cardiac MIBG uptake in individuals with parkinsonism can be an additional criterion for diagnosing PD. However, a normal result of cardiac MIBG in individuals with suspicious parkinsonian syndrome does not exclude the diagnosis of PD. The findings of cardiac MIBG studies contributed to elucidating the pathophysiology of PD. We investigated the sensitivity and specificity of cardiac MIBG scintigraphy in PD. A total of 54 studies with 3114 individuals diagnosed with PD were included. The data were described as means with a Hoehn and Yahr stage of 2.5 and early and delayed registration H/M ratios of 1.70 and 1.51, respectively. The mean cutoff for the early and delayed phases were 1.89 and 1.86. The sensitivity for the early and delayed phases was 0.81 and 0.83, respectively. The specificity for the early and delayed phases were 0.86 and 0.80, respectively.

Novel Meta-iodobenzylguanidine and Etoposide Complex: Physicochemical Characterization and Mathematical Modeling of Anticancer Activity

It is hypothesized that meta-iodobenzylguanidine (MIBG) complexation with etoposide (VP-16) will improve drug solubility and specificity towards BE(2)C neuroblastoma (NB) cells, 90% of which are known to be MIBG avid. After MIBG and VP-16 interaction, the dry complex was analyzed for crystalline structure, surface morphology, solubility, and size distribution by X-ray powder diffraction (P-XRD), scanning electron microscopy (SEM), infrared (FTIR) and UV spectroscopy, and dynamic light scattering. After exposure to the complex, the cell viability and decay rates were assessed by the MTS assay and estimated using exponential decay models (EDM). Multi-factorial ANOVA and an independent t-test were used to assess for cell viability and solubility data, respectively. The resulting (1: 3 w/w) VP-16: MIBG complex had a mean diameter and zeta potential of 458.5 nm and 0.951 mV, respectively. It dramatically increased the drug apparent water solubility (~ 12-folds). This was ascribed to the formation of a VP-16/MIBG nanocrystalline state mainly governed by cation-π interactions, evidenced by FTIR, SEM, and P-XRD data following the complexation. The EDM relating percent cell viability to drug concentration yielded an excellent fit (r2 > 0.95) and enabled to estimate the IC50 values of both native drug and its complex: 6.2 μM and 5.23 μM, respectively (indicating a conservation of drug anticancer activity). The statistical results were consistent with those of the exponential decay models, indicating that MIBG does not inhibit the anticancer activity of VP-16. This study indicates that the VP-16/MIBG complexation improves VP-16 solubility without antagonizing its anticancer activity. Moreover, the efficiency of the EDM for drug IC50 estimation provides alternative mathematical method for such in vitro cytotoxicity studies.

Biological Insight and Recent Advancement in the Treatment of Neuroblastoma

One of the most frequent solid tumors in children is neuroblastoma, which has a variety of clinical behaviors that are mostly influenced by the biology of the tumor. Unique characteristics of neuroblastoma includes its early age of onset, its propensity for spontaneous tumor regression in newborns, and its high prevalence of metastatic disease at diagnosis in individuals older than 1 year of age. Immunotherapeutic techniques have been added to the previously enlisted chemotherapeutic treatments as therapeutic choices. A groundbreaking new treatment for hematological malignancies is adoptive cell therapy, specifically chimeric antigen receptor (CAR) T cell therapy. However, due to the immunosuppressive nature of the tumor microenvironment (TME) of neuroblastoma tumor, this treatment approach faces difficulties. Numerous tumor-associated genes and antigens, including the MYCN proto-oncogene (MYCN) and disialoganglioside (GD2) surface antigen, have been found by the molecular analysis of neuroblastoma cells. The MYCN gene and GD2 are two of the most useful immunotherapy findings for neuroblastoma. The tumor cells devise numerous methods to evade immune identification or modify the activity of immune cells. In addition to addressing the difficulties and potential advancements of immunotherapies for neuroblastoma, this review attempts to identify important immunological actors and biological pathways involved in the dynamic interaction between the TME and immune system.

Nurses' Experiences Caring for Children With Neuroblastoma Receiving 131I-Metaiodobenzylguanidine Therapy: A Qualitative Descriptive Study

Background: Neuroblastoma, the most common extra-cranial solid tumor found in children, carries a high mortality rate due to challenges with metastatic disease at diagnoses and relapse. ¹³¹I-Metaiodobenzylguanidine (I-MIBG) therapy provides targeted radiotherapy to treat neuroblastoma, but requires children to be isolated for radiation exposure, with limited access to the healthcare team while hospitalized. There is minimal research outlining the nurses' perspectives on caring for this patient population. Therefore, the aim of this study was to describe the nurses' experiences caring for children receiving ¹³¹I-MIBG therapy, focusing on nursing care, challenges, radiation exposure, and preparation. Methods: Ten nurses were recruited using purposeful sampling for this qualitative descriptive study. Semi-structured interview guides and conventional qualitative content analysis guided the data collection and analysis. Results: Nurses overwhelmingly felt isolated from their patients and a decreased sense of connection with the child. Although nurses felt prepared, they had more anxiety with the first patient experience and identified that parent engagement was essential. Overall, nurses shared they had support from written materials outlining the protocols, and members of the multidisciplinary team. More concern for radiation exposure was expressed by nurses of childbearing age and with handling bodily fluids. Discussion: Findings suggest that nurses would benefit from simulation experiences to help prepare for radiation exposure safety, strategies to engage the family in the child's care, and interacting with a child in single-room isolation. Because programs differ around the US, additional research exploring nurses' experiences is warranted to evaluate the best successes in providing ¹³¹I-MIBG therapy.

Base-Mediated Radio-Iodination of Arenes by Using Organosilane and Organogermane as Radiolabelling Precursors

The radio-iodination of arenes is investigated from organosilane and organogermane precursors using ipso-electrophilic halogenation (IEH). Discovery of a mild base mediated process allows radio-iodination in HFIP (1,1,1,3,3,3-hexafluoro-2-propanol) of either aryl silane or germane, with germanes being more reactive. Clinical potential of arylgermanes as radio-iodination precursors is demonstrated through the labelling of [¹²⁵ I]IMTO (iodometomidate) and [¹²⁵ I]MIBG (meta-iodobenzylguanidine) thus offering an alternative to radio-iododestannylation processes using non-toxic precursors.

Metastatic pheochromocytoma and paraganglioma: a retrospective multicentre analysis on prognostic and predictive factors to chemotherapy

Background

Prognostic and predictive markers in metastatic pheochromocytoma and paraganglioma (mPPGL) are unknown. We aimed to evaluate epidemiology of mPPGL, and prognostic factors of overall survival (OS) and predictive markers of treatment duration with first-line chemotherapy (TD1L).

Patients and methods

Retrospective multicentre study of adult patients with mPPGL treated in Latin American centres between 1982 and 2021.

Results

Fifty-eight patients were included: 53.4% were female, median age at diagnosis of mPPGL was 36 years and 12.1% had a family history of PPGL. The primary site was adrenal, non-adrenal infradiaphragmatic and supradiaphragmatic in 37.9%, 34.5% and 27.6%, respectively. 65.5% had a functioning tumour and 62.1% had metachronous metastases. Positive uptakes were found in 32 (55.2%) ⁶⁸Gallium positron emission tomography (PET/CT), 27 (46.6%) 2-deoxy-2-[fluorine-18]fluoro-D-glucose PET/CT and 37 (63.8%) of ¹³¹Iodine-metaiodobenzylguanidine (MIBG) tests. Twenty-three (40%) patients received first-line chemotherapy, with cyclophosphamide, vincristine and dacarbazine used in 12 (52%) of patients. At a median follow-up of 62.8 months, median TD1L was 12.8 months. Either functional exams, tumour functionality, pathological characteristics or primary tumour location were significantly associated with response or survival. Yet, negative MIBG, Ki67 ≥ 10%, infradiaphragmatic location and functional tumours were associated with numerically inferior OS.

Conclusions

In patients with mPPGL, prognostic and predictive factors to chemotherapy are still unknown, but negative MIBG uptake, Ki67 ≥ 10%, infradiaphragmatic location and functional tumours were numerically linked to worse OS. Our results should be further validated in larger and independent cohorts.

The Experience of Children With Neuroblastoma and Their Parents During Single-Room Isolation for 131I-Metaiodobenzylguanidine Therapy: A Qualitative Descriptive Study

Background: Administration of ¹³¹I-metaiodobenzylguanidine (¹³¹I-MIBG) for neuroblastoma requires hospitalization in single-room isolation and limits caregiver physical contact due to the child's radioactive burden. Though used for decades, there is a dearth of research on the experiences of children and their parents while isolated. Methods: This qualitative descriptive study evaluated the experience of children with neuroblastoma undergoing single-room isolation for ¹³¹I-MIBG therapy and their parents. Ten nurses, nine parents, and five children were interviewed; transcripts were analyzed applying a conventional content analysis approach. Results: Child themes included overall experiences ranging from positive to negative; emotional stress was common; symptoms were common but mostly managed; the children were adequately prepared for isolation; and audiovisual technology and entertainment helped. The indwelling urinary catheter was a source of emotional stress and/or pain for several children. Parent themes included I thought it was going to be a lot worse; it gets better with time; feeling concerned and overwhelmed; prepared as much as you can be; and you feel like you're not alone. Discussion: Findings suggest that children and parents would benefit from additional coping support interventions to address emotional distress. Efforts should be made to identify other sources of technology or room designs that can maximize the child's sense of connection with parents and healthcare professionals. Additional research is needed to examine the impact of this isolation experience on the long-term psychological outcomes of children and parents.

Thyroid Dysfunction from Treatments for Solid Organ Cancers

In recent years, cancer care has been transformed by immune-based and targeted treatments. Although these treatments are effective against various solid organ malignancies, multiple adverse effects can occur, including thyroid dysfunction. In this review, the authors consider treatments for solid organ cancers that affect the thyroid, focusing on immune checkpoint inhibitors, kinase inhibitors, and radioactive iodine-conjugated treatments (I-131-metaiodobenzylguanidine). They discuss the mechanisms causing thyroid dysfunction, provide a framework for their diagnosis and management, and explore the association of thyroid dysfunction from these agents with patient survival.

Novel therapeutics and drug-delivery approaches in the modulation of glioblastoma stem cell resistance

Glioblastoma (GBM) is a deadly malignancy with a poor prognosis. An important factor contributing to GBM recurrence is high resistance of GBM cancer stem cells (GSCs). While temozolomide (TMZ), has been shown to consistently extend survival, GSCs grow resistant to TMZ through upregulation of DNA damage repair mechanisms and avoidance of apoptosis. Since a single-drug approach has failed to significantly alter prognosis in the past 15 years, unique approaches such as multidrug combination therapy together with distinctive targeted drug-delivery approaches against cancer stem cells are needed. In this review, a rationale for multidrug therapy using a targeted nanotechnology approach that preferentially target GSCs is proposed with discussion and examples of drugs, nanomedicine delivery systems, and targeting moieties.

Going Nuclear with Amino Acids and Proteins - Basic Biochemistry and Molecular Biology Primer for the Technologist

In recent years, there has been an influx of new tracers into the field of nuclear medicine and molecular imaging. Most of these tracers that have been FDA approved for clinical imaging exploit various mechanisms of protein biochemistry and molecular biology to bring about their actions, such as amino acid metabolism, protein folding, receptor-ligand interactions, and surface transport mechanisms. In this review, we attempt to paint a clear picture of the basic biochemistry and molecular biology of protein structure, translation, transcription, post-translational modifications, and protein targeting, in the context of the various radiopharmaceuticals currently used clinically, all in an easy-to-understand language for entry level technologists in the field. Tracer characteristics, including indications, dosage, injection-to-imaging time, and the logic behind the normal and pathophysiologic biodistribution of these newer molecular tracers, are also discussed.

Side effects of theragnostic agents currently employed in clinical practice

Nuclear medicine plays an increasingly important role in several neoplasms management through a theragnostic approach by which targeted molecular imaging and radiotherapy are obtained with the use of radionuclide pairs with similar characteristics. In some cases, nuclear theragnostic use a pair of agents with identical chemical and biological characteristics while in others are employed theragnostic molecules which are not chemically or biologically identical but show similar biodistribution (so-called "twins in spirit" radiopharmaceuticals). This strategy was developed for the first time over 75 years ago, when iodine-131 was used for diagnostic imaging, confirmation of target expression and radionuclide therapy of thyroid cancer. Other theragnostic approaches were subsequently introduced with significant clinical results and some of them are currently considered standard treatment for different cancers. However, as any other therapy, also nuclear theragnostic treatment carries the potential risk of early deterministic and late stochastic off-target adverse effects, generally minimal and easily managed. This article reviews the reported side effects and risks of the main radiopharmaceuticals used for nuclear theragnostic in oncology for the treatment of thyroid cancer, neuroendocrine neoplasms, adrenergic tumors, metastatic prostate cancer, and liver tumors. Selecting appropriate patients using a multidisciplinary approach, meticulous pretreatment planning and knowledge of methods permit to decrease the incidence of these potential side effects.

123I-Meta-Iodobenzylguanidine Single-Photon Emission Computerized Tomography/Computerized Tomography Scintigraphy in the Management of Neuroblastoma

Neuroblastoma is the most common pediatric extracranial solid tumor. High-risk neuroblastoma is the most frequent presentation with an overall survival of approximately 50%. ¹²³I-meta-iodobenzylguanidine (¹²³I-mIBG) scintigraphy in the assessment of the primary tumor and its metastases at diagnosis and after chemotherapy is a cornerstone imaging modality. In particular, the bulk of skeletal metastatic disease evaluated with ¹²³I-mIBG at diagnosis and the following chemotherapy has a prognostic value. Currently, single-photon emission computerized tomography/computerised tomography (SPECT/CT) is considered a fundamental part of ¹²³I-mIBG scintigraphy. ¹²³I-mIBG SPECT/CT is a highly specific and sensitive imaging biomarker and it has been the basis of all existing neuroblastoma trials requiring molecular imaging. The introduction of SPECT/CT has shown not only the heterogeneity of the mIBG uptake within the primary tumor but also the presence of completely mIBG nonavid metastatic lesions with mIBG-avid primary neuroblastomas. It is currently possible to semi-quantitatively assess tracer uptake with standardized uptake value, which allows a more precise evaluation of the tracer avidity and can help monitor chemotherapy response. The patchy mIBG uptake has consequences from a theranostic perspective and may partly explain the failure of some neuroblastomas to respond to ¹³¹I-mIBG molecular radiotherapy. Various positron emission tomography tracers, targeting different aspects of neuroblastoma cell biology, are being tested as possible alternatives to ¹²³I-mIBG.

Designing and Comparing Performances of Image Processing Pipeline for Enhancement of I-131-metaiodobenzylguanidine Images

Objective

An image processing pipeline can have more than one image processing technique in sequence, and the output of the first technique becomes input for the next technique and so on. In this study, we have designed and compared the performances of image processing pipelines for enhancement of I-131-metaiodobenzylguanidine (mIBG) images.

Materials and Methods

Five different image processing pipelines (A [Gaussian filter, normalization], B [histogram specification (image 1), Gaussian filter, normalization], C [histogram specification (image 2), Gaussian filter, normalization], D [{histogram specification (image 3), Gaussian filter, and normalization], and E [histogram specification (image 4), Gaussian filter, normalization]) were designed and their performances were evaluated on I-131-mIBG images (n = 122). The image quality was assessed objectively using Perception-based Image Quality Evaluator (PIQE) score and subjectively (on scale 1-4) by two nuclear medicine physician. Sign test was applied to find the statistically significant difference between the image quality obtained using image processing pipelines. We applied test of proportion to compute difference in proportion of image quality score assigned to images obtained using image processing pipelines.

Results

Based on PIQE score, the quality of images obtained using all the five image processing pipelines were significantly better than that of input images (P < 0.001). The highest image quality score (=4) was assigned maximum number of times (n = 90) to the images obtained using image processing pipeline D and was significantly different from that of the second best image processing pipeline E (P = 0.015).

Conclusions

The image processing pipeline D was found to be better for enhancement of I-131-mIBG images.

A review of pediatric neuroendocrine tumors, their detection, and treatment by radioisotopes

Neuroendocrine tumors (NETs) are rare in childhood. Neuroblastoma is the most common pediatric extracranial solid tumor, occurring >90% in children younger than 5 years of age. Pheochromocytoma and paraganglioma are rare NETs, causing hypertension in 0.5-2% of hypertensive children. Gastroenteropancreatic NETs can occur in children and are classified into carcinoids and pancreatic tumors. Nuclear medicine procedures have an essential role both in the diagnosis and treatment of NETs. Metaiodobenzylguanidine (MIBG) labeled with radioiodine has a well-established role in diagnosis as well as therapeutic management of the neuroblastoma group of diseases. During recent decades, establishing the abundant expression of somatostatin receptors by NETs first led to scintigraphy with somatostatin analogs (i.e. Tc/In-octreotide) and, later, with the emergence of positron-emitting labeled agents (i.e. Ga-DOTATATE/DOTATOC/DOTANOC) PET scans with significantly higher detection efficiency became available. Therapy with somatostatin analogs labeled with beta emitters such as Lu-177 and Y-90, known as peptide receptor radionuclide therapy, is a promising new option in the management of patients with inoperable or metastasized NETs. In this article, pediatric NETs are briefly reviewed and the role of radioactive agents in the detection and treatment of these tumors is discussed.

Immune Checkpoint Inhibitors: New Weapons Against Medullary Thyroid Cancer?

Medullary thyroid carcinoma is a rare neuroendocrine neoplasm that originates from thyroid C cells. Surgery, with complete resection of the tumor, is the only curative approach. However, in most cases, the tumor recurs at locoregional or metastatic level. In this setting, the management remains challenging. In recent years, the immune checkpoint inhibitors have provided promise for changing the cancer treatment paradigm through the application of new approaches that enhance the body's natural antitumor defenses. The aim of this review is to summarize and discuss available data on efficacy and safety of the Food and Drug Administration-approved immune checkpoint inhibitors in patients with medullary thyroid carcinoma. After an extensive search, we found 7 useful data sources (one single-case report, one short article with very preliminary data, five ongoing registered clinical trials). Despite the lack of published evidence regarding the use of immune check point inhibitors, it must be considered that all the ongoing registered clinical trials saw first light in the last three years, thus indicating a growing interest of researchers in this field. Results coming from these trials, and hopefully, in the next future, from additional trials, will help to clarify whether this class of drugs may represent a new weapon in favor of patients with medullary thyroid carcinoma.

The emerging role of cell surface receptor and protein binding radiopharmaceuticals in cancer diagnostics and therapy

Targeting specific cell membrane markers for both diagnostic imaging and radionuclide therapy is a rapidly evolving field in cancer research. Some of these applications have now found a role in routine clinical practice and have been shown to have a significant impact on patient management. Several molecular targets are being investigated in ongoing clinical trials and show promise for future implementation. Advancements in molecular biology have facilitated the identification of new cancer-specific targets for radiopharmaceutical development.

Para-aortic haemangioma mimics paraganglioma on MRI

Here, we report a case of a 70-year-old man referred for an incidentally discovered left renal lesion with peri-aortic lymphadenopathy following a CT scan for back pain. A follow-up MRI scan demonstrated a Bosniak IIF left renal cyst and a T2-hyperintense para-aortic lesion concerning for extra-adrenal paraganglioma (EAP). [¹³¹I] Metaiodobenzylguanidine scintigraphy of the para-aortic lesion and urine catecholamines were equivocal. The mass was resected via a robotic approach. Histological examination revealed a haemangioma. Haemangiomas are benign vascular tumours frequently identified on imaging of the liver. Intra-abdominal haemangiomas outside of the liver, however, are rare and may have imaging characteristics that mimic EAP.

Paediatric Horner Syndrome: How much further to investigate?

We report an infant with an early-onset Horner syndrome and normal urinary catecholamine levels. Further investigations with Nuclear medicine imaging with ¹²³I-MIBG (meta-iodo benzyl-guanidine) confirmed a right thoracic inlet mass consistent with a neuroblastoma, a tumor of neural crest origin. The authors emphasize the need for investigating idiopathic acquired pediatric Horner syndrome and the value of an MIBG scan as a diagnostic test for suspected neuroblastoma.

High-specific-activity iodine 131 metaiodobenzylguanidine for the treatment of metastatic pheochromocytoma or paraganglioma: a novel therapy for an orphan disease

PURPOSE OF REVIEW

Pheochromocytomas and paragangliomas represent less than 1% of all endocrine tumors. Approximately 15-20% of these tumors are malignant. The definition of malignancy relies on the presence of metastasis. Metastatic pheochromocytomas and paragangliomas are usually advanced, incurable tumors with limited therapeutic options. About 50-60% of these tumors express the noradrenaline transporter in their cell membranes. Recently, the United States Food and Drug Administration approved high-specific-activity iodine 131 metaiodobenzylguanidine (HSA-I-131-MIBG) for the treatment of metastatic pheochromocytomas and paragangliomas that express the noradrenaline transporter. This review reports the benefits and toxicity of HSA-I-131-MIBG, its physical and dosimetric aspects, and radiation safety precautions, as well as its potential therapeutic value for other malignancies (neuroblastoma, gastroenteropancreatic neuroendocrine tumors, and medullary thyroid carcinoma).

RECENT FINDINGS

A phase 2 clinical trial with HSA-I-131-MIBG reported an impressive clinical benefit rate, acceptable toxicity and long-term benefits.

SUMMARY

HSA-I-131-MIBG is an effective medication for metastatic pheochromocytomas and paragangliomas that express the noradrenaline transporter.

Theragnostic Aspects and Radioimmunotherapy in Pediatric Tumors

The use of theragnostic radiopharmaceuticals in nuclear medicine has grown rapidly over the years to combine the diagnosis and therapy of tumors. In this review, we performed web-based and desktop literature research to investigate and explain the potential role of theragnostic imaging in pediatric oncology. We focused primarily on patients with aggressive malignancies such as neuroblastoma and brain tumors, to select patients with the highest chance of benefit from personalized therapy. Moreover, the most critical and groundbreaking applications of radioimmunotherapy in children’s oncology were examined in this peculiar context. Preliminary results showed the potential feasibility of theragnostic imaging and radioimmunotherapy in pediatric oncology. They revealed advantages in the management of the disease, thereby allowing an intra-personal approach and adding new weapons to conventional therapies.

Recent advances in radiotracers targeting norepinephrine transporter: structural development and radiolabeling improvements

The norepinephrine transporter (NET) is a major target for the evaluation of the cardiac sympathetic nerve system in patients with heart failure and Parkinson's disease. It is also used in the therapeutic applications against certain types of neuroendocrine tumors, as exemplified by the clinically used ^123/131I-MIBG as theranostic single-photon emission computed tomography (SPECT) agent. With the development of more advanced positron emission tomography (PET) technology, more radiotracers targeting NET have been reported, with superior temporal and spatial resolutions, along with the possibility of functional and kinetic analysis. More recently, fluorine-18-labelled NET tracers have drawn increasing attentions from researchers, due to their longer radiological half-life relative to carbon-11 (110 min vs. 20 min), reduced dependence on on-site cyclotrons, and flexibility in the design of novel tracer structures. In the heart, certain NET tracers provide integral diagnostic information on sympathetic innervation and the nerve status. In the central nervous system, such radiotracers can reveal NET distribution and density in pathological conditions. Most radiotracers targeting cardiac NET-function for the cardiac application consistent of derivatives of either norepinephrine or MIBG with its benzylguanidine core structure, e.g. ¹¹C-HED and ¹⁸F-LMI1195. In contrast, all NET tracers used in central nervous system applications are derived from clinically used antidepressants. Lastly, possible applications of NET as selective tracers over organic cation transporters (OCTs) in the kidneys and other organs controlled by sympathetic nervous system will also be discussed.

Technology and precision therapy delivery in childhood cancer

PURPOSE OF REVIEW

The purpose of this review is to describe current advances in pediatric precision therapy through innovations in technology and engineering. A multimodal approach of chemotherapy, surgery and/or radiation therapy has improved survival outcomes for pediatric cancer but with significant early and late toxicities. The pediatric population is particularly vulnerable given their age during treatment. Advances in precision interventions discussed include image guidance, ablation techniques, radiation therapy and novel drug delivery mechanisms that offer the potential for more targeted approach approaches with improved efficacy while limiting acute and late toxicities.

RECENT FINDINGS

Image-guidance provides improved treatment planning, real time monitoring and targeting when combined with ablative techniques and radiation therapy. Advances in drug delivery including radioisotopes, nanoparticles and antibody drug conjugates have shown benefit in adult malignancies with increasing use in pediatrics. These therapies alone and combined may lead to augmented local antitumor effect while sparing systemic exposure and potentially limiting early and late toxicities.

SUMMARY

Pediatric cancer medicine often requires a multimodal approach, each with early and late toxicities. Precision interventions and therapies offer promise for more targeted approaches in treating pediatric malignancies and require further investigation to determine long-term benefit.

Theranostics: Leveraging Molecular Imaging and Therapy to Impact Patient Management and Secure the Future of Nuclear Medicine

Nuclear medicine is experiencing a renaissance, with U.S. Food and Drug Administration approval recently being obtained for theranostic agents and a wide variety of such agents soon to impact patient care significantly in the era of precision medicine. The NETTER-1 trial demonstrated the therapeutic effect of a theranostic agent in markedly improving progression-free survival in patients with metastatic gastroenteropancreatic neuroendocrine tumors. Predominantly retrospective studies have demonstrated a significant response to ¹⁷⁷Lu-labeled agents targeting prostate-specific membrane antigen (PSMA) in patients with prostate cancer. At least 2 prospective clinical trials involving ¹⁷⁷Lu-PSMA agents are under way that will likely pave the way for Food and Drug Administration approval in the United States. A significant upside to theranostics is that patients tend to tolerate these agents better than chemotherapy. Theranostic compounds are likely to impact many cancers in the near future, not only through improvements in quality of life but also in terms of survival. This article provides an overview of already approved agents as well as those on the horizon. It is important that as these agents are clinically onboarded, nuclear medicine physicians have the expertise to deploy theranostics safely and efficiently, ensuring that these agents attain and maintain their position as leading lines of therapy in managing patients with cancer as well as becoming an important aspect of nuclear medicine practice in the future.

A Durable Response With the Combination of Nivolumab and Cabozantinib in a Patient With Metastatic Paraganglioma: A Case Report and Review of the Current Literature

INTRODUCTION

Pheochromocytomas and sympathetic paragangliomas (PPGL) are neuroendocrine catecholamine-secreting tumors that are usually localized. Metastatic disease is rare and systemic treatment consists of conventional chemotherapy and high-specific-activity iodine-131-MIBG which was approved by the FDA in 2018. Although chemotherapy combinations still have value in specific settings, the debilitating side effects of treatment with only modest benefit have limited their use. With the introduction of a new generation of targeted therapy and immunotherapy patients with metastatic PPGL may have improved therapeutic options.

AREAS COVERED

The current paper presents a case of a patient with metastatic PPGL who received multiple lines of systemic treatment. Despite progression on previous single agent cabozantinib and single agent pembrolizumab on separate clinical trials, the patient has exhibited a major response to the combination of cabozantinib and nivolumab for the past 22 months. In addition, we will review the available therapies for metastatic PPGL and discuss novel agents under clinical development.

CONCLUSION

Newer targeted therapies and immunotherapy options are under clinical development with promising results for patients with PPGL.

Targeted Radionuclide Therapy for Patients with Metastatic Pheochromocytoma and Paraganglioma: From Low-Specific-Activity to High-Specific-Activity Iodine-131 Metaiodobenzylguanidine

Low-specific-activity iodine-131–radiolabeled metaiodobenzylguanidine (I-131-MIBG) was introduced last century as a potential systemic therapy for patients with malignant pheochromocytomas and paragangliomas. Collective information derived from mainly retrospective studies has suggested that 30–40% of patients with these tumors benefit from this treatment. A low index of radioactivity, lack of therapeutic standardization, and toxicity associated with intermediate to high activities (absorbed radiation doses) has prevented the implementation of I-131-MIBG’s in clinical practice. High-specific-activity, carrier-free I-131-MIBG has been developed over the past two decades as a novel therapy for patients with metastatic pheochromocytomas and paragangliomas that express the norepinephrine transporter. This drug allows for a high level of radioactivity, and as yet is not associated with cardiovascular toxicity. In a pivotal phase two clinical trial, more than 90% of patients achieved partial responses and disease stabilization with the improvement of hypertension. Furthermore, many patients exhibited long-term persistent antineoplastic effects. Currently, the high-specific-activity I-131-MIBG is the only approved therapy in the US for patients with metastatic pheochromocytomas and paragangliomas. This review will discuss the historical development of high-specific-activity I-131-MIBG, its benefits and adverse events, and future directions for clinical practice applicability and trial development.