The joint IAEA, EANM, and SNMMI practical guidance on peptide receptor radionuclide therapy (PRRNT) in neuroendocrine tumours

EANM position paper on the role of radiobiology in nuclear medicine

With an increasing variety of radiopharmaceuticals for diagnostic or therapeutic nuclear medicine as valuable diagnostic or treatment option, radiobiology plays an important role in supporting optimizations. This comprises particularly safety and efficacy of radionuclide therapies, specifically tailored to each patient. As absorbed dose rates and absorbed dose distributions in space and time are very different between external irradiation and systemic radionuclide exposure, distinct radiation-induced biological responses are expected in nuclear medicine, which need to be explored. This calls for a dedicated nuclear medicine radiobiology. Radiobiology findings and absorbed dose measurements will enable an improved estimation and prediction of efficacy and adverse effects. Moreover, a better understanding on the fundamental biological mechanisms underlying tumor and normal tissue responses will help to identify predictive and prognostic biomarkers as well as biomarkers for treatment follow-up. In addition, radiobiology can form the basis for the development of radiosensitizing strategies and radioprotectant agents. Thus, EANM believes that, beyond in vitro and preclinical evaluations, radiobiology will bring important added value to clinical studies and to clinical teams. Therefore, EANM strongly supports active collaboration between radiochemists, radiopharmacists, radiobiologists, medical physicists, and physicians to foster research toward precision nuclear medicine.

Effect of Peptide Dose on Radiation Dosimetry for Peptide Receptor Radionuclide Therapy with 177Lu-DOTATOC: A Pilot Study

Background:

Optimal peptide concentration in treatment with ¹⁷⁷Lu-DOTATOC/DOTATATE is a matter of debate. Most of the studies with peptide receptor radionuclide therapy mention peptide dose ranging between 100 and 250 μg. The aim of this is to identify possible differences in radiation-absorbed doses (D/Gy) to tumor and kidney as a function of the peptide mass dose in order to identify the most suitable peptide dose for treatment. The therapeutic index (D_tumor/D_kidneys) was assessed as a key parameter for the treatment response.

Materials and Methods:

Five patients with metastasized Grade 1 to Grade 2 neuroendocrine tumor were analyzed in this study. Patients (n = 4) received two cycles of treatment with intravenously injected ¹⁷⁷Lu-DOTATOC containing peptide mass doses of 200 μg and 90 μg, alternatively; one patient was treated with 90 μg peptide mass in both the therapy cycles. Whole-body (head to mid-thigh) three-dimensional single-photon emission computerized tomography (3D SPECT)/CT images were acquired at 1, 4, 24, 48, and 72 h following the injection of ¹⁷⁷Lu-DOTATOC. Attenuation correction for 3D SPECT images was performed using CT data acquired and fused with the SPECT data (SPECT/CT).

Results:

Overall, 28 target lesions (liver n = 17, lung n = 4, lymph nodes n = 1, and bone n = 2) were analyzed after 1^st and 2^nd therapy cycles. Tumor normalized absorbed doses varied by a factor of 74 between 0.35 and 26 mGy/MBq. Averaged over all patients, a higher normalized mean tumor dose (10.51 mGy/MBq) was achieved for a peptide dose of 200 μg compared to 90 μg (4.58 mGy/MBq). Kidneys doses varied by a factor of up to 4 between patients (0.25–1.0 mGy/MBq) (independent of dose cycle and peptide dose) and by a factor of up to 2 between dose cycles. The mean kidney dose was 13.7% higher for the 90 μg peptide dose compared to 200 μg. Given the higher tumor dose, the mean therapeutic index of a 200 μg mass dose was considerably higher (16.95), compared to a 90 μg mass dose (9.63). This coincided with the observation, that lesion volume reduction was more pronounced after an initial treatment with a 200 μg mass dose. Biologically effective dose was only 5. 1%–19.3% higher than the absorbed dose for individual dose cycles.

Conclusions:

Higher peptide dose of 200 μg appears to be more suitable than 90 μg in terms of tumor dose, kidney dose, and therapeutic index for treatment with ¹⁷⁷Lu-DOTATOC.

The internal dosimetry user group position statement on molecular radiotherapy

The Internal Dosimetry User Group (IDUG) is an independent, non-profit group of medical professionals dedicated to the promotion of dosimetry in molecular radiotherapy (www.IDUG.org.uk). The Ionising Radiation (Medical Exposure) Regulations 2017, IR(ME)R, stipulate a requirement for optimisation and verification of molecular radiotherapy treatments, ensuring doses to non-target organs are as low as reasonably practicable. For many molecular radiotherapy treatments currently undertaken within the UK, this requirement is not being fully met. The growth of this field is such that we risk digressing further from IR(ME)R compliance potentially delivering suboptimal therapies that are not in the best interest of our patients. For this purpose, IDUG proposes ten points of action to aid in the successful implementation of this legislation. We urge stakeholders to support these proposals and ensure national provision is sufficient to meet the criteria necessary for compliance, and for the future advancement of molecular radiotherapy within the UK.

Dosimetric optimization of nuclear medicine therapy based on the Council Directive 2013/59/EURATOM and the Italian law N. 101/2020. Position paper and recommendations by the Italian National Associations of Medical Physics (AIFM) and Nuclear Medicine (AIMN)

This recommendation by the Italian Associations of Nuclear Medicine (AIMN) and Medical Physics (AIFM) focuses on the dosimetric optimization of Nuclear Medicine Therapy (NMT) as clearly requested by the article 56 of the EURATOM Directive 2013/59 and its consequent implementation in article 158 in the Italian Law n. 101/2020. However, this statement must deal with scientific and methodological limits that still exist and, above all, with the currently available limited resources. This paper addresses these specific issues. It distinguishes among many possible kinds of NMT. For each type, dosimetric optimization is recommended or considered optional, according to the general criteria adopted in any human choice, i.e. a check of technical feasibility first, followed by a cost/benefit argument. The classification of therapies as standardized or non-standardized is presented. This is based on the complexity of the type of pathology, on the variability of the treatment outcome, and on the risks involved. According to the present document, which was officially delivered to Italian Health Ministry as necessary interpretation of the law, a therapeutic team can, in science and consciousness, overcome the indications of posology, to optimize and tailoring a treatment with dosimetry, on the basis of published national or international data or guidelines, without need of an Ethics Committee approval. Data collected in this way will provide additional evidence about optimal dosimetric reference values. As conclusion, a formal appeal is made to the European and National regulatory agencies for pharmaceuticals to obtain the official acknowledgment of this principle.

Role of Artificial Intelligence in Theranostics:: Toward Routine Personalized Radiopharmaceutical Therapies

We highlight emerging uses of artificial intelligence (AI) in the field of theranostics, focusing on its significant potential to enable routine and reliable personalization of radiopharmaceutical therapies (RPTs). Personalized RPTs require patient-specific dosimetry calculations accompanying therapy. Additionally we discuss the potential to exploit biological information from diagnostic and therapeutic molecular images to derive biomarkers for absorbed dose and outcome prediction; toward personalization of therapies. We try to motivate the nuclear medicine community to expand and align efforts into making routine and reliable personalization of RPTs a reality.

90Y/177Lu-DOTATOC: From Preclinical Studies to Application in Humans

The PRRT (Peptide Receptor Radionuclide Therapy) is a promising modality treatment for patients with inoperable or metastatic neuroendocrine tumors (NETs). Progression-free survival (PFS) and overall survival (OS) of these patients are favorably comparable with standard therapies. The protagonist in this type of therapy is a somatostatin-modified peptide fragment ([Tyr3] octreotide), equipped with a specific chelating system (DOTA) capable of creating a stable bond with β-emitting radionuclides, such as yttrium-90 and lutetium-177. In this review, covering twenty five years of literature, we describe the characteristics and performances of the two most used therapeutic radiopharmaceuticals for the NETs radio-treatment: [90Y]Y-DOTATOC and [177Lu]Lu-DOTATOC taking this opportunity to retrace the most significant results that have determined their success, promoting them from preclinical studies to application in humans.

Targeted radionuclide therapy: an emerging field in solid tumours

PURPOSE OF REVIEW

Targeted radionuclide therapy (TRNT) is characterized by systemic administration of radiolabelled drugs, targeting specific molecular alterations expressed on the tumour cells. Small molecules, labelled with β- or α- emitting radioisotopes, are used to deliver radiation directly to the tumour sites. Pretreatment imaging to visualize whole body biodistribution of the target, using the same drugs labelled with positron or γ-emitting radionuclides, completes the concept of theranostic. This review will briefly summarize the current clinical research findings and applications of TRNT in solid tumours, mostly focusing on neuroendocrine and prostate neoplasms.

RECENT FINDINGS

Peptide receptor radionuclide therapy is a major component in the management of gastroentropancreatic neuroendocrine tumours, with favourable safety profile, quality-of-life improvement and survival benefit. On the NETTER-1 study, it proved to be more effective than high-dose long-acting-release octreotide, leading to its regulatory approval. Prostate-specific membrane antigen (PSMA) is an excellent target for TRNT in prostate cancer. 177Lu-PSMA radioligand therapy demonstrated higher response rates in patients with metastatic castration resistant prostate cancer, when compared with second-line chemotherapy. New developments, including targeting of fibroblast activation proteins overexpressed in the tumour stroma, show promising preliminary results in the theranostic setting.

SUMMARY

Recent research has demonstrated and consolidated the use of TRNT against well established targets in neuroendocrine tumours and prostate cancer. The identification of new promising molecular targets for TRNT, will further expand the theranostic applications of radionuclides in the field of nuclear medicine.

Peptide Receptor Radionuclide Therapy and Primary Brain Tumors: An Overview

Primary brain tumors (PBTs) are some of the most difficult types of cancer to treat, and despite advancements in surgery, chemotherapy and radiotherapy, new strategies for the treatment of PBTs are needed, especially for those with poor prognosis such as inoperable/difficult-to-reach lesions or relapsing disease. In regard to the last point, malignant primary brain tumors remain some of the most lethal types of cancer. Nuclear medicine may provide exciting new weapons and significant contributions in the treatment of PBTs. In this review, we performed literature research in order to highlight the possible role of peptide receptor radionuclide therapy (PRRT) in the treatment of PBTs with radiolabeled molecules that bind with high-affinity transmembrane receptors such as somatostatin receptors (SSTRs), neurokinin type-1 receptor and prostate-specific membrane antigen (PSMA). These receptors are overexpressed in some cancer types such as gliomas, meningiomas, pituitary tumors and medulloblastomas. A comprehensive overview of possible applications in this field will be shown, providing knowledge about benefits, feasibility, developments and limitations of PRRT in this type of tumor, also revealing new advantages in the management of the disease.

Simple model for estimation of absorbed dose by organs and tumors after PRRT from a single SPECT/CT study

Background

Following each cycle of peptide receptor radionuclide therapy (PRRT), absorbed doses by tumors and normal organs are typically calculated from three quantitative single-photon emission computed tomography (SPECT)/computed tomography (CT) studies acquired at t₁ = 24 h, t₂ = 96 h, t₃ = 168 h after the first cycle of treatment and from a single study at t₁ after the subsequent cycles. In the present study, we have assessed the feasibility of a single SPECT/CT study after each PRRT cycle using a trained multiple linear regression (MLR) model for absorbed dose calculation and have evaluated its impact on patient management. Quantitative [¹⁷⁷Lu]-DOTA-TATE SPECT/CT data after PRRT of seventy-two consecutive metastatic neuroendocrine tumors patients were retrospectively evaluated. A set of 40 consecutive studies was used to train the MLR model. The two independent variables of the model included the time of imaging after administration of the treatment and the radiopharmaceutical activity concentration in a given  organ/tumor. The dependent variable was the dose absorbed by the organ/tumor obtained with the standard protocol. For bone marrow dosimetry, the independent variables included the time of imaging, and the blood and remainder of the body activity concentration. The model was evaluated in 32 consecutive patients. Absorbed doses were assessed for kidneys, bone marrow, liver, spleen and tumor sites.

Results

There was no difference in management decisions, whether PRRT can be safely continued or not because unsafe absorbed dose to risk organs between the standard and the MLR model-based protocol using a single SPECT/CT study performed at t₃ = 168 h after the first cycle and at t₁ = 24 h after the subsequent cycles. Cumulative absorbed doses were obtained with mean relative differences of − 0.5% ± 5.4%, 1.6% ± 15.1%, − 6.2% ± 7.3%, − 5.5% ± 5.8% and 2.9% ± 12.7% for kidneys, bone marrow, liver, spleen and tumors, respectively (Pearson’s r correlation coefficient 0.99, 0.91, 0.99, 0.99 and 0.97, respectively).

Conclusion

Dosimetry calculations using a MLR model with a single SPECT/CT study are in good agreement with the standard protocol, while avoiding the use of dosimetry software and enabling improved patient comfort and reduced scanner and staff time.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40658-021-00409-z.

Safe use of radiopharmaceuticals in patients with chronic kidney disease: a systematic review

BACKGROUND

Patients with chronic kidney disease (CKD) may need to have their radiopharmaceutical dosage adjusted to prevent adverse effects and poor outcomes, but there are few recommendations on radiopharmaceutical dosing for this group of patients. The aim of this study is to provide an overview of the available information on radiopharmaceutical dose recommendations for patients with CKD.

METHODS

We performed a systematic literature review according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. We conducted a literature search in the MEDLINE (PubMed) and Embase databases and screened potentially relevant studies using inclusion and exclusion criteria. We independently assessed the included observational studies' methodologies and extracted relevant data.

RESULTS

Of the 5795 studies first identified, 34 were included in this systematic review. These studies described three radiopharmaceuticals: [131I]sodium iodine, [18F]fludeoxyglucose, and [131I]iobenguane. Twenty-nine studies (85.3%) reported data on patients with CKD stage 5, while only three studies mentioned CKD patients in other stages (8.8%).

CONCLUSION

We found no consistent recommendations for radiopharmaceutical dosing in patients with CKD. Although some studies do mention dosing difficulties in patients with CKD, information is available for only a few radiopharmaceuticals, and recommendations are sometimes contradictory. Further research on radiopharmaceutical dosing in patients with CKD is needed to determine whether these patients require specific dosing, especially for therapeutic radiopharmaceuticals where a non-optimised dose may lead to an increased risk of toxicity for non-targeted organs. Including patients with CKD in studies and providing specific information about dosing in these patients should be a priority for the radiopharmaceutical community.

Therapeutic Multidose Preparation of a Ready-to-Use 177Lu-PSMA-617 Using Carrier Added Lutetium-177 in a Hospital Radiopharmacy and Its Clinical Efficacy

Introduction: [¹⁷⁷Lu]Lu-prostate-specific membrane antigen (PSMA)-617 has emerged as a promising radiopharmaceutical for targeting PSMA in metastatic castrate-resistant prostate carcinoma (mCRPC). We have optimized the radiolabeling protocol for a multidose formulation (27-28.8 GBq equivalent to 6-7 patient-doses) of [¹⁷⁷Lu]Lu-PSMA-617 using [¹⁷⁷Lu]Lu³⁺ produced via ¹⁷⁶Lu(n,γ)¹⁷⁷Lu route with moderate specific activity (0.66-0.81 GBq/μg). Methods: [¹⁷⁷Lu]Lu-PSMA-617 was synthesized using moderate specific activity [¹⁷⁷Lu]LuCl₃ (0.74 GBq/μg) with PSMA-617 having metal-to-ligand molar ratio ∼1: 2.5 in CH₃COONH₄ buffer (0.1 M) containing gentisic acid at pH 4.0-4.5. Human prostate carcinoma cell line LNCaP cell (high PSMA expression) was used for in vitro cell-binding studies and generating tumor xenograft models in nude mice for tissue biodistribution studies. Several batches of the present formulation have been clinically administered in mCRPC patients (single patient dose: 4.44-5.55 GBq per cycle). Results: In this study we report a consistent and reproducible protocol for multidose formulations of [¹⁷⁷Lu]Lu-PSMA-617 for adopting in a hospital radiopharmacy setting. Although the radiochemical yield of [¹⁷⁷Lu]Lu-PSMA-617 was found to be 97.30% ± 1.03%, the radiochemical purity was 98.24% ± 0.50% (n = 19). In vitro and serum stability of [¹⁷⁷Lu]Lu-PSMA-617 was retained up to 72 and 120 h after radiolabeling and upon storage at -20°C with a radioactive concentration between 0.37 and 0.74 GBq/mL upon using stabilizer concentration as low as 43-48 μg/mCi. Preclinical cell-binding studies of [¹⁷⁷Lu]Lu-PSMA-617 revealed specific binding with LNCaP cells of 17.4% ± 2.4%. The uptake in LnCaP xenografted tumor (nude mice) was 7.5 ± 2.6% ID/g for ∼1.5-2.0 cm³ tumor volume at 24-h post-injection. Post-therapy (24 h) SPECT image of mCRPC patients with prior orchidectomy and various hormone therapy showed specific localization of [¹⁷⁷Lu]Lu-PSMA-617 in the tumor region. Conclusions: Formulation of a ready-to-use multidose formulation of [¹⁷⁷Lu]Lu-PSMA-617 was successfully achieved and the procedure was optimized for routine preparation at a hospital radiopharmacy set-up. High degree of localization of [¹⁷⁷Lu]Lu-PSMA-617 in post-therapy SPECT scan and the post-therapeutic response confirms its therapeutic efficacy. Clinical Trials.gov ID: RPC/51/Minutes/Final dated 16th October, 2019.

Overview and Current Status of Peptide Receptor Radionuclide Therapy

Peptide receptor radionuclide therapy (PRRT) is an effective form of treatment of patients with metastatic neuroendocrine tumors, delivering modest objective tumor response rates but notable survival and symptomatic benefits. The first PRRT approved by the US Food and Drug Administration was lutetium 177-DOTATATE and is for use in adults with somatostatin receptor-positive gastroenteropancreatic neuroendocrine tumors. The treatment paradigm typically leads to significant improvement in symptomology coupled with an extended period of progression-free survival. Side effects are limited, with a small fraction of individuals experiencing clinically significant long-term renal or hematologic toxicity.

Kidney Protection with the Radical Scavenger α1-Microglobulin (A1M) during Peptide Receptor Radionuclide and Radioligand Therapy

α₁-Microglobulin (A1M) is an antioxidant found in all vertebrates, including humans. It has enzymatic reductase activity and can scavenge radicals and bind free heme groups. Infused recombinant A1M accumulates in the kidneys and has therefore been successful in protecting kidney injuries in different animal models. In this review, we focus on A1M as a radioprotector of the kidneys during peptide receptor radionuclide/radioligand therapy (PRRT/RLT). Patients with, e.g., neuroendocrine tumors or castration resistant prostate cancer can be treated by administration of radiolabeled small molecules which target and therefore enable the irradiation and killing of cancer cells through specific receptor interaction. The treatment is not curative, and kidney toxicity has been reported as a side effect since the small, radiolabeled substances are retained and excreted through the kidneys. In recent studies, A1M was shown to have radioprotective effects on cell cultures as well as having a similar biodistribution as the somatostatin analogue peptide ¹⁷⁷Lu-DOTATATE after intravenous infusion in mice. Therefore, several animal studies were conducted to investigate the in vivo radioprotective potential of A1M towards kidneys. The results of these studies demonstrated that A1M co-infusion yielded protection against kidney toxicity and improved overall survival in mouse models. Moreover, two different mouse studies reported that A1M did not interfere with tumor treatment itself. Here, we give an overview of radionuclide therapy, the A1M physiology and the results from the radioprotector studies of the protein.

Responsible Radionuclide Cancer Care

The landscape of nuclear oncology is rapidly changing. The advent of molecular radionuclide theranostics, multidisciplinary tumor board decision making, artificial intelligence and radiomics interpretation of diagnostic imaging, evolution of pharmacogenomics prediction of tumor response, and regulatory requirements for prospective individual dosimetry are just some of the elements which are broadening the essence of physician responsibility. The burgeoning knowledge base essential for mastering the emergent technologies, and their profound effect on moral philosophic aspects of provision of cancer care, are challenging. The new relationship of the theranostic nuclear physician with respect to shared care of the individual patient, particularly with regard to transparency, accountability, and responsibility for targeted radionuclide diagnosis and therapy of cancer, will be explored in this update.

Extramedullary Relapsed Multiple Myeloma Treatment With 177Lu-Labeled CXCR4 Endoradiotherapy and Dosimetric Results

ABSTRACT

We created our first national clinical protocol of 177Lu-CXCR4 therapy for patient who have failed to respond to current therapy options. We also calculated the kidney, liver, and tumor dosimetry. The kidney's mean absorbed dose was calculated to be 0.45 Gy/GBq, the calculated radiation absorbed dose of the liver was 0.63 Gy/GBq, and the radiation absorbed doses of the tumors vary between 9.2 and 82 Gy/GBq. 177Lu-CXCR4 therapy produced a promising clinical response in our patient in acceptable radiation dose limits as a treatment option in heavily pretreated patients with advanced multiple myeloma.

Intra-arterial administration boosts 177Lu-HA-DOTATATE accumulation in salvage meningioma patients

INTRODUCTION: Intravenous ¹⁷⁷Lu-(HA-)DOTATATE has shown promising results for the treatment of surgery- and radiotherapy-refractory meningiomas. We aimed to investigate the added value of intra-arterial administration. METHODS: Patients underwent at least one intravenous ¹⁷⁷Lu-HA-DOTATATE treatment first and subsequent intra-arterial cycles. In(tra)-patient comparison was based on post-treatment ¹⁷⁷Lu-HA-DOTATATE imaging 24 hours post-injection. Technical success rates and adverse events were recorded. RESULTS: Four patients provided informed consent. Technical success rate was 100% and no angiography related or unexpected adverse events occurred. Intra-patient comparison showed an increased target lesion accumulation on both planar imaging (mean +220%) and SPECT/CT (mean +398%) after intra-arterial administration compared to intravenous. No unexpected adverse events during follow-up occurred. CONCLUSION: Intra-arterial PRRT significantly increases tracer accumulation, and is a safe and promising improvement for salvage meningioma patients. Future prospective studies on intra-arterial PRRT are needed to determine gain on efficacy and survival.

Fibroblast activation protein inhibitor (FAPi) positive tumour fraction on PET/CT correlates with Ki-67 in liver metastases of neuroendocrine tumours

AIM

Gallium-68-labelled inhibitors of the fibroblast activation protein (FAPi) enable positron emission tomography/computed tomography (PET/CT) imaging of fibroblast activation. We evaluated if [⁶⁸Ga]Ga-DATA5 m.SA.FAPi PET/CT is related to Ki-67 as a marker of tumour aggressiveness in patients with liver metastases of NET.

METHODS

Thirteen patients with liver metastases of a histologically confirmed NET who underwent PET/CT with [⁶⁸Ga]Ga-DATA5 m.SA.FAPi, [18F]FDG and [⁶⁸Ga]Ga-DOTA-TOC were retrospectively analyzed. PET-positive liver tumour volumes were segmented for calculation of volume, SUVmax and PET-positive tumour fraction (TF). PET parameters were correlated with Ki-67.

RESULTS

FDG_SUVmax correlated positively (rho = 0.543, p < 0.05) and DOTATOC_SUVmax correlated negatively (rho = -0.618, p < 0.05) with Ki-67, the correlation coefficients were in the moderate range. There was no significant correlation between FAPi_SUVmax and Ki-67 (rho = 0.382, p > 0.05). FAPi_TF correlated positively (rho = 0.770, p < 0.01) and DOTATOC_TF correlated negatively (rho = -0.828, p < 0.01) with Ki-67, both significantly with high correlation coefficients. FDG_TF also correlated significantly with Ki-67, with a moderate correlation coefficient (rho = 0.524, p < 0.05). The ratio FAPi_VOL:DOTATOC_VOL showed a significant and strong correlation with Ki-67 (rho = 0.808, p < 0.01).

CONCLUSION

The ratio FAPi_VOL:DOTATOC_VOL might serve as a clinical parameter for the assessment of dedifferentiation and aggressiveness of liver metastases in patients with NET. [⁶⁸Ga]Ga-DATA5 m.SA.FAPi might hold potential for identification of high-risk patients. Further studies are warranted to evaluate its prognostic significance in comparison to [¹⁸F]FDG in patients with NET.

Theranostics in Nuclear Medicine: Emerging and Re-emerging Integrated Imaging and Therapies in the Era of Precision Oncology

Theranostics refers to the pairing of diagnostic biomarkers with therapeutic agents that share a specific target in diseased cells or tissues. Nuclear medicine, particularly with regard to applications in oncology, is currently one of the greatest components of the theranostic concept in clinical and research scenarios. Theranostics in nuclear medicine, or nuclear theranostics, refers to the use of radioactive compounds to image biologic phenomena by means of expression of specific disease targets such as cell surface receptors or membrane transporters, and then to use specifically designed agents to deliver ionizing radiation to the tissues that express these targets. The nuclear theranostic approach has sparked increasing interest and gained importance in parallel to the growth in molecular imaging and personalized medicine, helping to provide customized management for various diseases; improving patient selection, prediction of response and toxicity, and determination of prognosis; and avoiding futile and costly diagnostic examinations and treatment of many diseases. The authors provide an overview of theranostic approaches in nuclear medicine, starting with a review of the main concepts and unique features of nuclear theranostics and aided by a retrospective discussion of the progress of theranostic agents since early applications, with illustrative cases emphasizing the imaging features. Advanced concepts regarding the role of fluorine 18-fluorodeoxyglucose PET in theranostics, as well as developments in and future directions of theranostics, are discussed. ^©RSNA, 2020 See discussion on this article by Greenspan and Jadvar.

The Dependence of Renal 68Ga[Ga]-DOTATOC Uptake on Kidney Function and Its Relevance for Peptide Receptor Radionuclide Therapy with 177Lu[Lu]-DOTATOC

Background: In addition to its SSTR-specific binding in tumors and healthy tissues, DOTATOC analogues accumulate in kidney parenchyma. Renal tracer uptake might be a surrogate of kidney function or dysfunction. This study aimed to evaluate if kidney function can be estimated from ⁶⁸Ga[Ga]-DOTATOC uptake in PET/CT and its impact on the nephrotoxicity of ¹⁷⁷Lu[Lu]-DOTATOC PRRT. Methods: Two cohorts of patients (A: 128 diagnostic patients; B: 32 PRRT patients) were evaluated retrospectively. SUV values of the kidneys, physiologically SSTR-expressing organs and in background compartments were assessed. Kidney function was calculated as eGFR by CKD-EPI creatinine equation. Pearson’s correlation coefficients and treatment-induced changes of uptake and kidney function were assessed and compared. Results: Kidney function and renal DOTATOC uptake showed a significant inverse correlation (R² = 0.037; p = 0.029). Evaluated models of PET/CT measurements were not able to predict kidney function sufficiently. The uptake of other organs did not depend on eGFR. While the renal uptake increased after PRRT (p < 0.001), the kidney function did not change significantly (p = 0.382). Neither low pre-therapeutic eGFR nor high pre-therapeutic kidney uptake were risk factors of PRRT-induced deterioration in kidney function. Conclusion: The relevance of kidney function for renal ⁶⁸Ga[Ga]-DOTATOC uptake is limited. The nephrotoxicity of ¹⁷⁷Lu[Lu]-DOTATOC PRRT might be low and cannot be reliably predicted by pre-therapeutic measurements.

Targeted α-Emitter Therapy of Neuroendocrine Tumors

Neuroendocrine tumors (NET) are a heterogeneous group of neoplasms, arising from cells of the endocrine system, with various clinical behaviors. Although these neoplasms are considered rare, a significant increase in the incidence and detectability of NET has been noted in many epidemiological studies in recent years. Among the various therapeutic options, peptide receptor radionuclide therapy (PRRT), using somatostatine has been shown to be highly effective and a well-tolerated therapy, improving survival parameters. The current use of radionuclides for PRRT is β-emitters. Due to hypoxia cancer tissue could be resistant for β-emitters. Quite long penetration range had a significant impact on side effects. α-particles with higher energy and shorter penetration range in comparison to β-particles, have distinct advantages for use in targeted therapy. The clinical experience with somatostatine based targeted α therapy (TAT) in NET showed very promising results even in patienicts refractory to treatment with β-emitters. This article summarizes current developments in preclinical and clinical investigation on TAT in NET.

Ga-68 DOTATATE PET/CT and F-18 FDG PET/CT in the evaluation of low and intermediate versus high-grade neuroendocrine tumors

OBJECTIVE

We investigated the role of Ga-68 DOTATATE PET/CT in comparison to F-18 FDG PET/CT in patients with low and intermediate versus high-grade neuroendocrine tumors (NETs).

METHODS

We identified 81 patients who underwent Ga-68 DOTATATE PET/CT at our institution between May 2017 and December 2018 and met inclusion criteria of biopsy-proven NET with known Ki-67 index, histologic grade, or differentiation. Patients were divided into two groups. Control group included Ki-67 ≤20%, grade 1 or 2, or well-differentiated tumors. Experimental group included Ki-67 >20%, grade 3, or poorly-differentiated tumors.

RESULTS

Mean age was 57 years, with 36 males and 45 females. Most common primary sites were small bowel, pancreas, and lung. Most common distant metastatic sites were liver and bone. In the control group (n = 67), median Ki-67 was 4% (range 1-30%). 55/67 (82.1%) DOTATATE and 6/11 (54.5%) FDG scans were positive (P = 0.04). Positive scans showed >10 lesions in 25/55 (45.5%) DOTATATE and 1/6 (16.7%) FDG scans (P = 0.18). 40/55 (72.7%) positive DOTATATE and 3/6 (50%) FDG scans showed distant disease (P = 0.25). In the experimental group (n = 14), median Ki-67 was 68% (range 25-95%). All 14 DOTATATE and all nine FDG scans were positive. Positive scans showed >10 lesions in 4/14 (28.6%) DOTATATE and 5/9 (55.6%) FDG scans (P = 0.20). 10/14 (71.4%) positive DOTATATE and 7/9 (77.8%) FDG scans showed distant disease (P = 0.74).

CONCLUSION

All patients with high grade, poorly-differentiated NETs had positive DOTATATE PET/CTs. In these patients, DOTATATE PET/CT did not significantly differ from FDG PET/CT in identifying >10 lesions or distant disease.

Emerging Preclinical and Clinical Applications of Theranostics for Nononcological Disorders

Studies in nuclear medicine have shed light on molecular imaging and therapeutic approaches for oncological and nononcological conditions. Using the same radiopharmaceuticals for diagnosis and therapeutics of malignancies, the theranostics approach, has improved clinical management of patients. Theranostic approaches for nononcological conditions are recognized as emerging topics of research. This review focuses on preclinical and clinical studies of nononcological disorders that include theranostic strategies. Theranostic approaches are demonstrated as possible in the clinical management of infections and inflammations. There is an emerging need for randomized trials to specify the factors affecting validity and efficacy of theranostic approaches in nononcological diseases.

Monte Carlo simulation of the acquisition conditions for 177Lu molecular imaging of hepatic tumors

OBJECTIVE

To examine the impact of acquisition time on Lutetium-177 (177Lu) single-photon emission computed tomography (SPECT) images using Monte Carlo simulation.

METHODS

A gamma camera simulation based on the Monte Carlo method was performed to produce SPECT images. The phantom was modeled on a NEMA IEC BODY phantom including six spheres as tumors. After the administration of 7.4 GBq of 177Lu, radioactivity concentrations of the tumor/liver at 6, 24, and 72 h after administration were set to 1.85/0.201, 2.12/0.156, and 1.95/0.117 MBq/mL, respectively. In addition, the radioactivity concentrations of the tumor at 72 h after administration varied by 1/2, 1/4, and 1/8 when comparison was made. Acquisition times examined were 1.2, 1.5, 2, 3, 6, and 12 min. To assess the impact of collimators, SPECT data acquired at 72 h after the administration using six collimators of low-energy high-resolution (LEHR), extended low-energy general-purpose (ELEGP), medium-energy, and general-purpose (MEGP-1, MEGP-2, and MEGP-3) and high-energy general-purpose (HEGP) were examined. After prefiltering using a Butterworth filter, projection images were reconstructed using ordered subset expectation maximization. The detected photons were classified into direct rays, scattered rays, penetrating rays, and characteristic X-rays from lead. The image quality was evaluated through visual assessment, and physical assessment of contrast recovery coefficient (CRC) and contrast-to-noise ratio (CNR). In this study, the CNR threshold for detectability was assumed to be 5.0.

RESULTS

To compare collimators, the highest sensitivity was observed with ELEGP, followed by LEHR and MEGP-1. The highest ratio of direct ray was also observed in ELEGP followed by MEGP-1. In comparison of the radioactivity concentration ratios of tumor/liver, CRC and CNR were significantly decreased with smaller radioactivity concentration ratios. This effect was greater with larger spheres. According to the visual assessment, the acquisition time of 6, 6, and 3 min or longer was required using ELEGP collimator at 6, 24, and 72 h after administration, respectively. Physical assessment based on CNR and CRC also suggested that 6, 6, and 3 min or longer acquisition time was necessary at 6, 24, and 72 h after administration.

CONCLUSION

177Lu-SPECT images generated via the Monte Carlo simulation suggested that the recommended acquisition time was 6 min or longer at 6 and 24 h and 3 min or longer at 72 h after administration.

Kidney doses in 177Lu-based radioligand therapy in prostate cancer: Is dose estimation based on reduced dosimetry measurements feasible?

The radiation dose to the kidneys should be monitored in prostate cancer patients treated with radioligand therapy (RLT) targeting the prostate-specific membrane antigen (PSMA). We analyzed whether pretherapeutic kidney function is predictive of subsequent kidney dose and to what extend the cumulative kidney dose after multiple therapy cycles at the end of treatment can be predicted from a dosimetry based on the first cycle. Methods: Data of 59 patients treated with at least 2 cycles of ¹⁷⁷Lu-PSMA-617 (PSMA-RLT) were analyzed. Treatment (median: 6 GBq/cycle) was performed at 6-8 week intervals, accompanied by voxel-based 3D-dosimetry (measured kidney dose) with SPECT/CT on each of days 0-3 and once during days 6-9. Pretherapeutic kidney function (eGFR, MAG3-clearance) was correlated to the kidney doses. Cumulative kidney doses at the end of treatment were compared to a dose estimation based on the population-based mean kidney dose, individual first cycle kidney dose and mean kidney doses of cycles 1, 3 and 5 per administered activity. Results: A total of 176 PSMA-RLT cycles were performed with a median of 3 cycles per patient. The average kidney dose per administered activity of all 176 cycles was 0.67 ± 0.24 Gy/GBq (range 0.21 - 1.60). MAG3-clearance and eGFR were no reliable predictors of subsequent absorbed kidney dose and showed only small effect sizes (R² = 0.080 and 0.014, P = 0.039 and 0.375). All simplified estimations of cumulative kidney dose correlated significantly (P < 0.001) with measured kidney doses: Estimations based on the individual first-cycle dose were more accurate than the use of the population-based average kidney dose (R² = 0.853 vs. R² = 0.560). Dose estimation was best when the doses of cycles 3 and 5 were included as well (R² = 0.960). Conclusion: Pretherapeutic renal function was not predictive for subsequent kidney dose during therapy. Extrapolation of individual data from dosimetry of the first cycle was highly predictive for the cumulative kidney dose at the end of treatment. This is further improved by the integration of dose information from every other cycle. In any case, because of a high interindividual variance, an individual dosimetry is advisable.

Peptide Receptor Radionuclide Therapy in the Management of Neuroendocrine Tumors (Neoplasms): Fundamentals and Salient Clinical Practice Points for Medical Oncologists

This editorial commentary is an expert summary of “Peptide Receptor Radionuclide Therapy (PRRT),” encompassing the essential fundamentals and salient clinical practice points, deliberated and designed in a point-wise manner with theme-based subheadings. Emphasis has been laid on the topics of practical relevance to the referring oncologists with relevant finer points where necessary. A part of the presented overview has been generated from the authors' own practical experience of more than 3500 successful therapies delivered over the last 9 years at a large tertiary care PRRT setting by the joint efforts of Radiation Medicine Centre (RMC), Bhabha Atomic Research Centre (BARC), and Gastrointestinal services of Tata Memorial Hospital (TMH) at the TMH-RMC premises. While the technical indigenization is beyond the scope of this treatise, we must mention here that India had been one of the frontrunners in this treatment modality, and the PRRT services in this country were developed purely as an indigenous effort right from the production of the radionuclide (177-Lutetium) at the reactor and radiolabeling and production of the radiopharmaceutical (177Lu-DOTATATE) by the radiopharmaceutical scientists at the BARC and RMC; such an endeavor allowed this very specialized therapy to be delivered at a very affordable cost in our setting which could be viewed as a major societal contribution of the atomic energy research in this country.

Outcomes after high-dose radiation in the management of neuroendocrine neoplasms

BACKGROUND

Neuroendocrine neoplasms (NENs) comprise a rare and heterogenous group of cancers, for which the role of radiation therapy continues to evolve. The purpose of this study is to analyze oncologic outcomes after the use of high-dose radiation in management of NENs at a tertiary hospital.

MATERIALS AND METHODS

We performed a retrospective review of patients who received high-dose radiation with intent to cure or provide durable local control (defined as biologically effective dose (BED) ≥40, α/β = 10) for a localized or metastatic NEN from 2006 to 2019. Evaluation of disease status after radiation was performed according to Response Evaluation Criteria in Solid Tumors (RECIST) criteria when possible. Patients were grouped by differentiation (well-differentiated (WD) or poorly-differentiated (PD)) and stage (localized/locally advanced disease (L) or metastatic (M)) in analysis of probabilities of progression after radiation.

RESULTS

45 patients completed a radiation course with BED ≥40 for a NEN (median BED 72). With a median follow-up of 24 months after radiation, the 2-year actuarial rates of local relapse-free survival, new metastasis-free survival, progression-free survival, and overall survival after radiation were 98%, 45%, 41%, and 69%, respectively. 25 patients (56%) developed new metastases after completion of radiation, including 33% (n = 3) of patients with WD-L disease, 44% (n = 8) of WD-M, 77% (n = 10) of PD-L, and 80% (n = 4) of PD-M, with progressively shorter median times to progression (26, 9, 8, and 3 months, respectively; p = 0.093). Of the 25 patients evaluable by RECIST, 68% (n = 17) achieved either a complete or partial best response in the irradiated lesion.

CONCLUSIONS

These data suggest that focal, high-dose radiation has a role in the management of selected patients with NENs. Local failure is rare in patients with both well-differentiated and poorly-differentiated disease, although the predominant pattern of failure remains development of new metastases.

The Outcome and Safety of Re-challenge Lutetium-177 PSMA (177Lu-PSMA) Therapy with Low-Dose Docetaxel as a Radiosensitizer-a Promising Combination in Metastatic Castrate-Resistant Prostate Cancer (mCRPC): a Case Report

Prostate-specific membrane antigen (PSMA)-directed radioligand therapy (PSMA-RLT) with lutetium-177 (177Lu-PSMA) has been used in metastatic castrate-resistant prostate cancer (mCRPC), and retrospective data have shown this therapy to be favourably safe with attractive clinical responses. Re-challenge 177Lu-PSMA therapy in early responders has been shown to be safe and effective. We report the use of low-dose Taxol-based chemotherapy (modified dose 25 mg/m2 weekly × 6 weeks) as a radiosensitizer with re-challenge 177Lu-PSMA therapy (4 cycles). In a period of 3 years, the patient underwent a total of 8 cycles of 177Lu-PSMA with a cumulative dose of 51.8 GBq. All therapies were uneventful and well tolerated. There was a good response to re-challenge 177Lu-PSMA therapy and low-dose docetaxel (Taxol-177Lu-PSMA) with no recorded tumour resistance.

A Rapid and Safe Infusion Protocol for 177Lu Peptide Receptor Radionuclide Therapy

Peptide receptor radionuclide therapy (PRRT) with ¹⁷⁷Lu-labeled somatostatin analogs in patients with somatostatin receptor-expressing tumors is often performed using administration protocols prescribing a 30-min infusion time. The most often used method of infusion is the gravity method, by which the complete dose is effectively administered exponentially. However, there is no evidence to explicitly support an infusion time of 30 min. This study aims to investigate the safety of an infusion time of less than 5 min. Methods: A cohort study was performed, examining the biochemical and clinical toxicity after PRRT when using a fast-infusion protocol with a maximum infusion time of 5 min. Data on patient characteristics, laboratory tests, follow-up visits, and pre- and posttreatment imaging using ⁶⁸Ga-DOTATOC PET/CT from patients treated with PRRT at the University Medical Center Utrecht (UMC Utrecht) were collected. All patients receiving PRRT using the fast-infusion protocol were included. If no laboratory or clinical follow-up was available, patients were excluded. In addition, a laboratory experiment was performed, simulating the standard-infusion protocol using the gravity method. Results: Thirty-one patients, treated using the fast-infusion protocol, were included. Clinical toxicity mainly consisted of grade 1/2 fatigue (87.1%) and grade 1 nausea or vomiting (67.7%) during follow-up. No acute or long-term clinical toxicity possibly related to the fast-infusion protocol was reported. Grade 3/4 hematologic toxicity occurred after PRRT in 1 patient (3.2%). No grade 3/4 renal toxicity occurred. The laboratory experiment showed that when using the gravity method for infusion, half of the activity is infused after 3.5 min, and 95% is infused within 15 min. Conclusion: A faster infusion of PRRT using an infusion time of less than 5 min is safe and feasible in clinical practice.

Peptide Receptor Radionuclide Therapy in Patients With Neurofibromatosis Type 2: Initial Experience

PURPOSE

Neurofibromatosis type 2 (NF2) is a genetic disorder that is associated with multiple tumors of the nervous system, and approximately one half of patients present with meningiomas. For patients with multifocal disease, somatostatin receptor-targeted peptide receptor radionuclide therapy (PRRT) might be a suitable systemic treatment option.

PATIENTS AND METHODS

Between March 2015 and August 2017, 11 NF2 patients (7 females and 4 males; mean age, 39 ± 12 years) with multifocal, progressive meningiomas underwent a median of 4 cycles of PRRT (range, 2-6 cycles). Acute and chronic adverse events were recorded according to National Institutes of Health's Common Toxicity Criteria (CTC) version 5.0. Follow-up MRIs (every 3 to 6 months), using the Response Assessment in Neuro-Oncology response criteria for meningiomas, were used to assess treatment responses.

RESULTS

Peptide receptor radionuclide therapy was well tolerated in all patients without any relevant acute adverse effects. Transient hematologic toxicity (CTC grade 3) was observed in 2 subjects. Somatostatin receptor-directed radiopeptide therapy resulted in radiological disease stabilization in 6 of 11 patients. Median progression-free survival was 12 months (range, 1-55 months), and overall survival was 37 months (range, 5-61 months).

CONCLUSIONS

Based on our retrospective pilot data, PRRT is feasible and well-tolerated in NF2 patients. It might offer a suitable treatment option in subjects with multiple, recurrent, or treatment-refractory meningiomas.

Theragnostics in Neuroendocrine Tumors

Several studies have demonstrated the effectiveness of somatostatin receptor (SSTR)-targeted imaging for diagnosis, staging, evaluating the possibility of treatment with cold somatostatin analogs, as well peptide receptor radionuclide therapy (PRRT), and evaluation of treatment response. PET with ⁶⁸Ga-labeled somatostatin analogs provides excellent sensitivity and specificity for diagnosing and staging neuroendocrine tumors (NETs). Metabolic imaging with PET with fludeoxyglucose ¹⁸F/computed tomography (CT) complements the molecular imaging with ⁶⁸Ga-SSTR PET/CT toward a personalized therapy in NET patients. The documented response rate of PRRT in NET summing up complete response, partial response, minor response, and stable disease is 70% to 80%.

Comparison of pretherapeutic osseous tumor volume and standard hematology for prediction of hematotoxicity after PSMA-targeted radioligand therapy

Purpose

Hematotoxicity is a potentially dose-limiting adverse event in patients with metastasized castration-resistant prostate cancer (mCRPC) undergoing prostate-specific membrane antigen (PSMA)-directed radioligand therapy (RLT). We aimed to identify clinical or PSMA-targeted imaging-derived parameters to predict hematological adverse events at early and late stages in the treatment course.

Methods

In 67 patients with mCRPC scheduled for ¹⁷⁷Lu-PSMA-617 RLT, pretherapeutic osseous tumor volume (TV) from ⁶⁸Ga-PSMA-11 PET/CT and laboratory values were assessed. We then tested the predictive capability of these parameters for early and late hematotoxicity (according to CTCAE vers. 5.0) after one cycle of RLT and in a subgroup of 32/67 (47.8%) patients after four cycles of RLT.

Results

After one cycle, 10/67 (14.9%) patients developed leukocytopenia (lymphocytopenia, 39/67 [58.2%]; thrombocytopenia, 17/67 [25.4%]). A cut-off of 5.6 × 10³/mm³ for baseline leukocytes was defined by receiver operating characteristics (ROC) and separated between patients with and without leukocytopenia (P < 0.001). Baseline leukocyte count emerged as a stronger predictive factor in multivariate analysis (hazard ratio [HR], 33.94, P = 0.001) relative to osseous TV (HR, 14.24, P = 0.01). After four cycles, 4/32 (12.5%) developed leukocytopenia and the pretherapeutic leukocyte cut-off (HR, 9.97, P = 0.082) tended to predict leukocytopenia better than TV (HR, 8.37, P = 0.109). In addition, a cut-off of 1.33 × 10³/mm³ for baseline lymphocytes separated between patients with and without lymphocytopenia (P < 0.001), which was corroborated in multivariate analysis (HR, 21.39, P < 0.001 vs. TV, HR, 4.57, P = 0.03). After four cycles, 19/32 (59.4%) developed lymphocytopenia and the pretherapeutic cut-off for lymphocytes (HR, 46.76, P = 0.007) also demonstrated superior predictive performance for late lymphocytopenia (TV, HR, 5.15, P = 0.167). Moreover, a cut-off of 206 × 10³/mm³ for baseline platelets separated between patients with and without thrombocytopenia (P < 0.001) and also demonstrated superior predictive capability in multivariate analysis (HR, 115.02, P < 0.001 vs.TV, HR, 12.75, P = 0.025). After four cycles, 9/32 (28.1%) developed thrombocytopenia and the pretherapeutic cut-off for platelets (HR, 5.44, P = 0.048) was also superior for the occurrence of late thrombocytopenia (TV, HR, 1.44, P = 0.7).

Conclusions

Pretherapeutic leukocyte, lymphocyte, and platelet levels themselves are strong predictors for early and late hematotoxicity under PSMA-directed RLT, and are better suited than PET-based osseous TV for this purpose.

The development and validation of a high performance liquid chromatography method to determine the radiochemical purity of [177Lu]Lu-HA-DOTA-TATE in pharmaceutical preparations

Lutetium-177 [¹⁷⁷Lu] tetra-azacyclododecanetetra-acetic acid [DOTA]-(Tyr3)-octreotate [TATE] ([¹⁷⁷Lu]Lu-DOTA-TATE) is a radiopeptide used for peptide receptor radionuclide therapy in patients with neuroendocrine tumours (NETs). This radiopeptide is made by labelling the ligand octreotate with Lutetium-177 using the linker DOTA. After labelling, and before clinical application quality control of the radiopeptide is needed and the radiochemical purity is assessed. Acceptance limits for radiochemical purity should be within 90-110% of the label claim for radiopharmaceuticals for diagnostic use and within 95-105% of the label claim for radiopharmaceuticals for therapeutic use. Moreover, the amount of unlabelled [¹⁷⁷Lu]LuCl₃ cannot exceed 2% of the radioactive dose. Since no monograph is available for [¹⁷⁷Lu]Lu-DOTA-TATE in the European Pharmacopeia (Ph Eur), this article describes the development and validation of a high-performance liquid chromatography (HPLC) method with ultraviolet (UV) detection and radiodetection. A Waters Acquity Arc UHPLC system equipped with a Waters 2998 photodiode array (PDA) detector was used coupled to a Berthold Lb 514 Flowstar detector equipped with a BGO-X gamma measuring cell. A reversed phase Symmetry Shield C18 column (4.6 mm × 250 mm, 5 µm) was used for chromatographic separation. A flow of 1.5 mL/min was maintained during analysis, using 0.1% TFA in water as mobile phase A and 0.1% TFA in ACN as mobile phase B. The retention time was around 1.7 min and 13.5 min for [¹⁷⁷Lu]LuCl₃ and [¹⁷⁷Lu]Lu-HA-DOTA-TATE, respectively. Stock solutions of [¹⁷⁷Lu]LuCl₃ were made by serial dilution and were injected to test for linearity, accuracy and precision, carry over and signal-to-noise ratio. A [¹⁷⁷Lu]Lu-HA-DOTA-TATE sample was prepared and injected to determine the carry over. The results showed that the method is linear over a range of 0.300-130 MBq/mL, which covers the range for clinical samples, provided that the clinical sample is diluted ten times before analysis. The LLOQ can be measured accurately even after dilution, with a signal-to-noise ratio of at least 5. In short, the method is accurate, precise and sensitive and can be implemented as part of the quality control of [¹⁷⁷Lu]Lu-HA-DOTA-TATE.

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

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

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

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

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

Imaging and liquid biopsy in the prediction and evaluation of response to PRRT in neuroendocrine tumors: implications for patient management

Purpose

The aim of this narrative review is to give an overview on current and emerging imaging methods and liquid biopsy for prediction and evaluation of response to PRRT. Current limitations and new perspectives, including artificial intelligence, are discussed.

Methods

A literature review of PubMed/Medline was performed with representative keywords. The search included articles published online through August 31, 2020. All searches were restricted to English language manuscripts.

Results

Peptide radio receptor therapy (PRRT) is a prospectively evaluated and approved therapy option in neuroendocrine tumors (NETs). Different ligands targeting the somatostatin receptor (SSTR) are used as theranostic pairs for imaging NET and for PRRT. Response assessment in prospective trials often relies on the morphological RECIST 1.1 criteria, based on lesion size in CT or MRI. The role of SSTR-PET and quantitative uptake parameters and volumetric data is still not defined. Monoanalyte tumor marker chromogranin A has a limited value for response assessment after PRRT. New emerging liquid biopsy techniques are offering prediction of response to PRRT and prognostic value.

Conclusions

New response criteria for NET patients undergoing PRRT will comprise multiparametric hybrid imaging and blood-based multianalyte markers. This represents tumor biology and heterogeneity.

Radiological and Clinical Efficacy of Intra-Arterial 90Y-DOTATATE in Patients with Unresectable, Progressive, Liver Dominant Neuroendocrine Neoplasms

This study was performed to determine if intra-arterial (i.a.) administration of ⁹⁰Y DOTATATE can provide an effective and safe alternative to the accepted standard for i.v. of peptide receptor radionuclide therapy (PRRT) in liver-dominant metastases of gastrointestinal pancreatic neuroendocrine neoplasm (GEP-NEN). A single site, prospective, preliminary case series study included 39 patients with histologically proven liver-dominant NEN. PRRT in the form of 1.15GBq ⁹⁰Y DOTATATE was given selectively into the liver via radiological catheterization of the hepatic artery, up to four times. The endpoint was radiological response (RECIST). Secondary endpoints assessed clinical well-being post-treatment, progression-free survival (PFS), overall survival (OS), and toxicity. Partial response (PR) was noted in 13% of subjects six weeks post-therapy, increasing to 24% at six months and dropping to 13% at 36 months. Disease progression (DP) was not seen at six weeks, was 5% at six months, and 47% at 36 months. Clinical response based on PS seen in 74% of patients at six weeks, 69% at six months, and 39% at 36 months had PFS and OS, respectively, of 22.7 months and 38.2 months. There was no difference in OS/PFS between those with RECIST PR and SD. One patient had significant toxicity (3%). Use of i.a. PRRT appears to be safe and effective in treating patients with liver-dominant NEN. In addition, the best OS (51 vs. 22 months) was seen when i.a. was used as an upfront treatment of bulky GEP-NEN liver metastases and not after i.v. ⁹⁰Y DOTATATE. The use of i.a. ⁹⁰Y DOTATATE PRRT appears to be safe and effective in treating patients with liver-dominant NEN.

Simultaneous Visualization of 161Tb- and 177Lu-Labeled Somatostatin Analogues Using Dual-Isotope SPECT Imaging

The decay of terbium-161 results in the emission of β¯-particles as well as conversion and Auger electrons, which makes terbium-161 interesting for therapeutic purposes. The aim of this study was to use dual-isotope SPECT imaging in order to demonstrate visually that terbium-161 and lutetium-177 are interchangeable without compromising the pharmacokinetic profile of the radiopharmaceutical. The ¹⁶¹Tb- and ¹⁷⁷Lu-labeled somatostatin (SST) analogues DOTATOC (agonist) and DOTA-LM3 (antagonist) were tested in vitro to demonstrate equal properties regarding distribution coefficients and cell uptake into SST receptor-positive AR42J tumor cells. The radiopeptides were further investigated in AR42J tumor-bearing nude mice using the method of dual-isotope (terbium-161/lutetium-177) SPECT/CT imaging to enable the visualization of their distribution profiles in the same animal. Equal pharmacokinetic profiles were demonstrated for either of the two peptides, irrespective of whether it was labeled with terbium-161 or lutetium-177. Moreover, the visualization of the sub-organ distribution confirmed similar behavior of ¹⁶¹Tb- and ¹⁷⁷Lu-labeled SST analogues. The data were verified in quantitative biodistribution studies using either type of peptide labeled with terbium-161 or lutetium-177. While the radionuclide did not have an impact on the organ distribution, this study confirmed previous data of a considerably higher tumor uptake of radiolabeled DOTA-LM3 as compared to the radiolabeled DOTATOC.

Current and future perspectives on functional molecular imaging in nephro-urology: theranostics on the horizon

In recent years, a paradigm shift from single-photon-emitting radionuclide radiotracers toward positron-emission tomography (PET) radiotracers has occurred in nuclear oncology. Although PET-based molecular imaging of the kidneys is still in its infancy, such a trend has emerged in the field of functional renal radionuclide imaging. Potentially allowing for precise and thorough evaluation of renal radiotracer urodynamics, PET radionuclide imaging has numerous advantages including precise anatomical co-registration with CT images and dynamic three-dimensional imaging capability. In addition, relative to scintigraphic approaches, PET can allow for significantly reduced scan time enabling high-throughput in a busy PET practice and further reduces radiation exposure, which may have a clinical impact in pediatric populations. In recent years, multiple renal PET radiotracers labeled with 11C, 68Ga, and 18F have been utilized in clinical studies. Beyond providing a precise non-invasive read-out of renal function, such radiotracers may also be used to assess renal inflammation. This manuscript will provide an overview of renal molecular PET imaging and will highlight the transformation of conventional scintigraphy of the kidneys toward novel, high-resolution PET imaging for assessing renal function. In addition, future applications will be introduced, e.g. by transferring the concept of molecular image-guided diagnostics and therapy (theranostics) to the field of nephrology.

Prospective Within-Patient Assessment of the Impact of an Unlabeled Octreotide Pre-dose on the Biodistribution and Tumor Uptake of 68Ga DOTATOC as Assessed by Dynamic Whole-body PET in Patients with Neuroendocrine Tumors: Implications for Diagnosis and Therapy

PURPOSE

Gastroenteropancreatic neuroendocrine tumors (GEP NETs) are often associated with high expression of somatostatin receptors (SSTRs) which allows for PET/CT imaging with radiolabeled somatostatin analogs such as ⁶⁸Ga-DOTATOC. The interplay between ⁶⁸Ga-DOTATOC and the synthetic somatostatin analogs commonly used to manage patient symptoms may lead to competition between the labelled and unlabeled peptides for receptor binding sites and current product labelling recommends patients be taken off somatostatin analogs before imaging. In this study, we prospectively investigated in human patients the effect of a pre-dose of octreotide, a short-acting somatostatin analog, on the distribution of ⁶⁸Ga-DOTATOC in GEP NETs and normal organs.

PROCEDURE

Research participants with GEP NETs were studied on two occasions using dynamic whole-body ⁶⁸Ga-DOTATOC PET/CT. The two imaging studies were performed within 21 days of each other, using an identical acquisition protocol except for the administration of 50 μg of short-acting octreotide (pre-dose) immediately before the second PET/CT. Paired t-tests were used to compare tracer uptake with and without octreotide, for tumor and various normal organs.

RESULTS

Seven participants with a mean age of 53 ± 10 years were studied. Octreotide pre-dosing decreased radiotracer uptake in the normal liver and spleen by 25 % (p = 0.04) and 47 % (p = 0.05) respectively but did not significantly change uptake in tumor (p = 0.53), red marrow (p = 0.12), kidneys (p =0.57), or pituitary gland (p = 0.27).

CONCLUSIONS

Our data indicate SSTR imaging can be improved with a pre-dose of unlabeled octreotide given just prior to injection of the radiotracer. These data suggest there may be no need to discontinue somatostatin analog therapy prior to PET/CT with ⁶⁸Ga-DOTATOC, allowing for a simpler, less disruptive patient protocol. This approach warrants further study in a variety of settings.

Tissue dose estimation after extravasation of 177Lu-DOTATATE

Background

Extravasation of radiopharmaceuticals used for vectorized internal radiotherapy can lead to severe tissue damage (van der Pol et al., Eur J Nucl Med Mol Imaging 44:1234–1243, 2017). Clinical management of these extravasations requires the preliminary estimation of the dose distribution in the extravasation area. Data are scarce regarding the dose estimation in the literature. This work presents a methodology for estimating the dose distribution after an extravasation occurred in September 2017, in the arm of a patient during a 7.4-GBq infusion of Lutathera ® (AAA).

Methods

A local quantification procedure initially developed for renal dosimetry was used. A calibration factor was determined and verified by phantom study. Extravasation volume of interest and its variation in time were determined using 4 whole body (WB) planar acquisitions performed at 2 h (T_2h), 5 h (T_5h), 20 h (T_20h), and 26 h (T_26h) after the beginning of the infusion and three SPECT/CT thoracic acquisitions at T_5h, T_20h, and T_26h. For better estimation of initial extravasation volume, 3 volumes were defined on SPECT images using a 3D activity threshold. Cumulated activities and associated absorbed doses (D₁, D₂, D₃) were calculated in the 3 volumes using the MIRD formalism.

Results

Volumes estimated using 3D threshold were V₁ = 1000 mL, V₂ =400 mL, and V₃ =180 mL. Cumulated activities were evaluated using a monoexponential fit on activities calculated on SPECT images. Estimated local absorbed doses in V₁, V₂, and V₃ were D₁ = 2.3 Gy, D₂ = 4.1 Gy, and D₃ = 6.8 Gy. Evolution in time of local activity in the extravasation area was consistent with an effective local half-life (T_eff) of 2.3 h.

Conclusions

Rapid local dose estimation was permitted thanks to knowledge of the calibration factor determined previous to accidental extravasation. Lutathera® lymphatic drainage was quick in the arm (T_eff = 2.3h). Estimated doses were in the lower range of deterministic effects and far under soft tissue necrosis threshold. Thus, no surgical rinse was proposed. The patient did not show any clinical consequence of the extravasation.

Assessment of γ-H2AX and 53BP1 Foci in Peripheral Blood Lymphocytes to Predict Subclinical Hematotoxicity and Response in Somatostatin Receptor-Targeted Radionuclide Therapy for Advanced Gastroenteropancreatic Neuroendocrine Tumors

BACKGROUND

We aimed to characterize γ-H2AX and 53BP1 foci formation in patients receiving somatostatin receptor-targeted radioligand therapy, and explored its role for predicting treatment-related hematotoxicity, and treatment response.

METHODS

A prospective analysis of double-strand break (DSB) markers was performed in 21 patients with advanced gastroenteropancreatic neuroendocrine tumors. γ-H2AX and 53BP1 foci formation were evaluated in peripheral blood lymphocytes (PBLs) at baseline, +1 h and +24 h after administration of 7.4 GBq (¹⁷⁷Lu)Lu-DOTA-TATE. Hematotoxicity was evaluated using standard hematology. Therapy response was assessed using (⁶⁸Ga)Ga-DOTA-TATE PET/CT before enrollment and after 2 cycles of PRRT according to the volumetric modification of RECIST 1.1.

RESULTS

DSB marker kinetics were heterogeneous among patients. Subclinical hematotoxicity was associated with γ-H2AX and 53BP1 foci formation (e.g., change in platelet count vs change in γ-H2AX⁺ cells between baseline and +1 h (r = -0.6080; p = 0.0045). Patients showing early development of new metastases had less γ-H2AX (p = 0.0125) and less 53BP1 foci per cell at +1 h (p = 0.0289), and demonstrated a distinct kinetic pattern with an absence of DSB marker decrease at +24 h (γ-H2AX: p = 0.0025; 53BP1: p = 0.0008).

CONCLUSIONS

Assessment of γ-H2AX and 53BP1 foci formation in PBLs of patients receiving radioligand therapy may hold promise for predicting subclinical hematotoxicity and early treatment response.

Nephrotoxicity/renal failure after therapy with 90Yttrium- and 177Lutetium-radiolabeled somatostatin analogs in different types of neuroendocrine tumors: a systematic review

BACKGROUND/OBJECTIVE

Data regarding the nephrotoxicity of the peptide receptor radionuclide therapy (PRRT) with Yttrium- and Lutetium-radiolabeled somatostatin analogs (RSA) are inconclusive. We aimed to evaluate the short- and long-term nephrotoxicity following PRRT usage in patients with all types of neuroendocrine tumors (NETs).

METHODS

A systematic review of observational studies reporting data about nephrotoxicity after treatment with Yttrium and Lutetium RSA was performed. Data on serum creatinine, creatinine clearance, glomerular filtration rate (GFR) and need for renal replacement therapy were compiled. We included patients with progressive, inoperable symptomatic G1, G2 and G3 different types of NETs. After searching in three electronic databases PubMed, Scopus and the Cochrane Library, from 1 January 1978 to November 2018, data were extracted and summarized using a random-effects model.

RESULTS

The final analysis included 34 studies, comprising 5386 participants, enrolling patients with G1, G2, G3 NETs and a follow-up from 12 up to 191 months. Compared with renal function before treatment, measured/estimated glomerular filtration rate (m/eGFR) values changed after PRRT, with a mean annual decrease following PRRT between 2 and 4 mL/min/1.73 m suggesting different grades of nephrotoxicity after PRRT. When compared, Y-RSA and the Y-RSA-Lu-RSA combination are associated with a higher m/eGFR decline compared to Lu-RSA alone.

CONCLUSIONS

PRRT can be followed by potentially serious long-term nephrotoxicity, despite kidney protection. The use of the quantified renal function combined with a long follow-up period and personalized dosimetry-based PRRT can reduce nephrotoxicity, in order to use the whole PRRT potential in the management of NETs.

The effect of calibration factors and recovery coefficients on 177Lu SPECT activity quantification accuracy: a Monte Carlo study

BACKGROUND

Different gamma camera calibration factor (CF) geometries have been proposed to convert SPECT data into units of activity concentration. However, no consensus has been reached on a standardised geometry. The CF is dependent on the selected geometry and is further affected by partial volume effects. This study investigated the effect of two CF geometries and their corresponding recovery coefficients (RCs) on the quantification accuracy of 177Lu SPECT images using Monte Carlo simulations.

METHODS

The CF geometries investigated were (i) a radioactive-sphere surrounded by non-radioactive water (sphere-CF) and (ii) a cylindrical phantom uniformly filled with radioactive water (cylinder-CF). Recovery coefficients were obtained using the sphere-CF and cylinder-CF, yielding the sphere-RC and cylinder-RC values, respectively, for partial volume correction (PVC). The quantification accuracy was evaluated using four different-sized spheres (15.6-65.4 ml) and a kidney model with known activity concentrations inside a cylindrical, torso and patient phantom. Images were reconstructed with the 3D OS-EM algorithm incorporating attenuation, scatter and detector-response corrections. Segmentation was performed using the physical size and a small cylindrical volume inside the cylinder for the sphere-CF and cylinder-CF, respectively.

RESULTS

The sphere quantification error (without PVC) was better for the sphere-CF (≤ - 5.54%) compared to the cylinder-CF (≤ - 20.90%), attributed to the similar geometry of the quantified and CF spheres. Partial volume correction yielded comparable results for the sphere-CF-RC (≤ 3.47%) and cylinder-CF-RC (≤ 3.53%). The accuracy of the kidney quantification was poorer (≤ 22.34%) for the sphere-CF without PVC compared to the cylinder-CF (≤ 2.44%). With PVC, the kidney quantification results improved and compared well for the sphere-CF-RC (≤ 3.50%) and the cylinder-CF-RC (≤ 3.45%).

CONCLUSION

The study demonstrated that upon careful selection of CF-RC combinations, comparable quantification errors (≤ 3.53%) were obtained between the sphere-CF-RC and cylinder-CF-RC, when all corrections were applied.

Prognostic and Theranostic Applications of Positron Emission Tomography for a Personalized Approach to Metastatic Castration-Resistant Prostate Cancer

Metastatic castration-resistant prostate cancer (mCRPC) represents a condition of progressive disease in spite of androgen deprivation therapy (ADT), with a broad spectrum of manifestations ranging from no symptoms to severe debilitation due to bone or visceral metastatization. The management of mCRPC has been profoundly modified by introducing novel therapeutic tools such as antiandrogen drugs (i.e., abiraterone acetate and enzalutamide), immunotherapy through sipuleucel-T, and targeted alpha therapy (TAT). This variety of approaches calls for unmet need of biomarkers suitable for patients’ pre-treatment selection and prognostic stratification. In this scenario, imaging with positron emission computed tomography (PET/CT) presents great and still unexplored potential to detect specific molecular and metabolic signatures, some of whom, such as the prostate specific membrane antigen (PSMA), can also be exploited as therapeutic targets, thus combining diagnosis and therapy in the so-called “theranostic” approach. In this review, we performed a web-based and desktop literature research to investigate the prognostic and theranostic potential of several PET imaging probes, such as ¹⁸F-FDG, ¹⁸F-choline and ⁶⁸Ga-PSMA-11, also covering the emerging tracers still in a pre-clinical phase (e.g., PARP-inhibitors’ analogs and the radioligands binding to gastrin releasing peptide receptors/GRPR), highlighting their potential for defining personalized care pathways in mCRPC.

Strategies Towards Improving Clinical Outcomes of Peptide Receptor Radionuclide Therapy

PURPOSE OF REVIEW

Peptide receptor radionuclide therapy (PRRT) with [177Lu-DOTA0,Tyr3] octreotate is an effective and safe second- or third-line treatment option for patients with low-grade advanced gastroenteropancreatic (GEP) neuroendocrine neoplasms (NEN). In this review, we will focus on possible extensions of the current use of PRRT and on new approaches which could further improve its treatment efficacy and safety.

RECENT FINDINGS

Promising results were published regarding PRRT in other NENs, including lung NENs or high-grade NENs, and applying PRRT as neoadjuvant or salvage therapy. Furthermore, a diversity of strategic approaches, including dosimetry, somatostatin receptor antagonists, somatostatin receptor upregulation, radiosensitization, different radionuclides, albumin binding, alternative renal protection, and liver-directed therapy in combination with PRRT, have the potential to improve the outcome of PRRT. Also, novel biomarkers are presented that could predict response to PRRT. Multiple preclinical and early clinical studies have shown encouraging potential to advance the clinical outcome of PRRT in NEN patients. However, at this moment, most of these strategies have not yet reached the clinical setting of randomized phase III trials.

Predictive and Prognostic Impact of Blood-Based Inflammatory Biomarkers in Patients with Gastroenteropancreatic Neuroendocrine Tumors Commencing Peptide Receptor Radionuclide Therapy

Tumor microenvironment inflammation contributes to the proliferation and survival of malignant cells, angiogenesis, metastasis, subversion of adaptive immunity, and reduced treatment response. We aimed to evaluate the early predictive and prognostic significance of markers of systemic inflammation in patients receiving somatostatin-receptor targeted peptide receptor radionuclide therapy (PRRT). This retrospective observational cohort study included 33 patients with advanced gastro-entero-pancreatic neuroendocrine tumors (GEP-NETs) treated with PRRT. Pretreatment blood-based inflammatory biomarkers, e.g., C-reactive protein levels (CRP), white blood cell count (WBC), and absolute neutrophil count (ANC), were documented and inflammation indexes, e.g., neutrophil-lymphocyte ratio (NLR) and Platelet × CRP multiplier (PCM), were calculated. Tumor burden was determined using [⁶⁸Ga]Ga-DOTA-TATE PET/CT before enrollment and every 2 cycles thereafter until progression. Therapy response was assessed using RECIST 1.1, including its volumetric modification. Inflammatory biomarkers and inflammatory indexes demonstrated marked heterogeneity among patients, and were significantly higher in non-responders (e.g., CRP (p < 0.001), ANC (p = 0.002), and PCM (p < 0.001)). Change in whole-body tumor burden after two cycles of PRRT was significantly associated with CRP (p = 0.0157) and NLR (p = 0.0040) in multivariate regression analysis. A cut-off of 2.5 mg/L for CRP (AUC = 0.84, p = 0.001) revealed a significant outcome difference between patients with adversely high vs. low CRP (median PFS 508 days vs. not yet reached (HR = 4.52; 95% CI, 1.27 to 16.18; p = 0.02)). Tumor-driven systemic inflammatory networks may be associated with treatment response, change in tumor burden, and prognosis in patients with GEP-NETs receiving PRRT.

Peptide Receptor Radionuclide Therapy of Pulmonary Neuroendocrine Neoplasms: a Single-Centre Experience

Purpose

Peptide receptor radionuclide therapy represents a therapeutic option for neuroendocrine neoplasms; to date, experiences with peptide receptor radionuclide therapy of pulmonary neuroendocrine neoplasms are still limited. We report our experience with peptide receptor radionuclide therapy of pulmonary neuroendocrine neoplasm patients.

Materials and Methods

Clinical records of 14 pulmonary neuroendocrine neoplasm patients (7 female and 7 male) who received at least 2 cycles of peptide receptor radionuclide therapy were retrospectively reviewed. Tumoural uptake of somatostatin analogues at pre-treatment imaging was graded as 2 to 3 in all patients. RECIST criteria were used to evaluate response.

Results

No treated patient had significant toxicity. Partial response was found in 3 (21.4%) patients, stable disease in 7 (50%), and progressive disease in 4 (28.6%). A statistically significant difference between disease state at enrolment and after peptide receptor radionuclide therapy was found.

Conclusions

Our data furtherly support peptide receptor radionuclide therapy as a safe and effective treatment of patients affected by pulmonary neuroendocrine neoplasms allowing disease control in about 71% of patients without showing significant toxicity. Other studies are needed to confirm our results.

Clinical efficacy of first and second series of peptide receptor radionuclide therapy in patients with neuroendocrine neoplasm: a cohort study

OBJECTIVES

Peptide receptor radionuclide therapy (PRRT) is an established treatment for metastatic neuroendocrine neoplasms (NEN). However, only limited data exists for the effect of multiple series of PRRT. The aim of this study was to investigate PFS and OS inNEN patients treated with multiple series of PRRT conforming to the ENETS treatment protocol.

METHODS

We included all patients with gastrointestinal (GI), pancreatic and bronchopulmonary (BP) NEN treated with PRRT from 2008 to 2018. We used Kaplan-Meier estimation to evaluate PFS and OS with subgroup analysis of primary tumor, Ki67-index, type of radioisotope and number of PRRT series.

RESULTS

133 patients (female/male 61/72) were included, median age 70 (interquartile range 64-76) years. GI-NEN comprised 62%, pancreatic 23% and BP 11%. Median Ki67-index was 5%. After first PRRTG1- and G2-tumors had PFS of 25 and 22 months, compared to 11 months in G3-NENs (p < .05) and PFS was longer in G1/G2 GI-NENs than BP-NEN (30vs. 12 months, p < .05). After retreatment with a second series of PRRT, the overall PFS (G1-G3) was 19 months, with G1- and G2-tumors having the highest PFS of 19 and 22 months, respectively. Overall, the GI and BP tumors had an OS of 54 and 51 months.

CONCLUSIONS

PRRT is an effective therapy with long-term PFS and OS, especially in G1 and G2 NENs, and with better prognosis in GI-NEN compared with BP-NENs. OS and PFS was shorter after the second series of PRRT compared with the first, however results were still encouraging.

18Fluorine-fluorodeoxyglucose PET/CT Imaging in Childhood Malignancies

Objectives:

The aim of the study was to evaluate the utility of ¹⁸fluorine-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) in the diagnosis, staging, restaging, and treatment response of childhood malignancies.

Methods:

This study included 52 patients (32 boys, 20 girls) who were referred to our clinic between November 2008 and December 2018 with the diagnosis of malignancy. The patients were evaluated retrospectively. Median age of the patients was 13 years (range 2-17). ¹⁸F-FDG was given to the patients intravenously, and time of flight with PET/16 slice CT was performed 1 hour thereafter. The lowest dose was 2 mCi (74 MBq) and the highest dose was 10 mCi (370 MBq). Fasting blood sugars of all patients were found below 200 mg/dL (11.1 mmol/L).

Results:

¹⁸F-FDG PET/CT was performed to evaluate the response to treatment in 38 of 52 children, staging in 11 patients (staging and evaluation of the response to treatment in nine of them), restaging in 2 patients, restaging, and evaluation of the response to treatment in 1 patient. ¹⁸F-FDG PET/CT examination was reported as normal in 13 patients (5 girls, 8 boys). The pathological ¹⁸F-FDG uptake was detected in 39 patients (14 girls, 25 boys), which indicated metastasis and/or recurrence of the primary disease. Total number of deaths was 30 (13 girls, 17 boys).

Conclusion:

¹⁸F-FDG PET/CT has a significant role for staging, restaging, treatment response, and detection of metastatic disease but it is limited for the early diagnosis of childhood cancers