Neuroendocrine tumors of the bronchopulmonary system (typical and atypical carcinoid tumors): current strategies in diagnosis and treatment. Conclusions of an expert meeting February 2011 in Weimar, Germany

Neuroendocrine tumors (NETs; syn. carcinoid tumors) are highly or moderately differentiated neoplasms. They comprise a large variety of rare and heterogeneous tumors with an estimated incidence of 3-5/100,000/year. They can arise in virtually every internal organ, but mainly occur in the gastroenteropancreatic and bronchopulmonary systems. Around 25% of the NETs are localized in the bronchopulmonary system. Approximately 2% of all lung tumors are NETs. According to the World Health Organization (WHO) classification of lung tumors, bronchopulmonary NETs are subdivided into typical carcinoids (TCs) and atypical carcinoids (ACs). The parameter with the highest impact on NET behavior and prognosis is the histological classification and staging according to the tumor/node/metastasis (TNM) system. The diagnosis of NETs is established by histological examination and the immunohistochemical detection of general neuroendocrine markers, such as chromogranin A (CgA) and synaptophysin. Serum markers and the use of functional imaging techniques are important additive tools to establish the diagnosis of a NET. The only curative option for lung NETs is complete surgical resection. Beyond that, the currently available interdisciplinary therapeutic options are local ablation, biotherapy (somatostatin analogues), or chemotherapy. New therapeutic options such as peptide receptor radionuclide therapy (PRRT) and molecularly targeted therapies achieve promising results and are under further evaluation. This report is a consensus summary of the interdisciplinary symposium 'Neuroendocrine Tumors of the Lung and of the Gastroenteropancreatic System (GEP NET) - Expert Dialogue' held on February 25-26, 2011 in Weimar, Germany. At this conference, a panel of 23 German experts shared their knowledge and exchanged their thoughts about research, diagnosis, and clinical management of NETs, whereby special attention was paid to NETs of the respiratory tract.

Differential expression and prognostic value of the chemokine receptor CXCR4 in bronchopulmonary neuroendocrine neoplasms

Introduction

For many tumors, the overexpression of the chemokine receptor CXCR4 is associated with increased malignancy and poor patient outcomes. However, comprehensive data for neuroendocrine neoplasms of the lung are still lacking.

Methods

CXCR4 expression was evaluated in a panel of bronchopulmonary neuroendocrine neoplasms (BP-NEN) comprising typical carcinoids (n = 26), atypical carcinoids (n = 30), and small cell lung cancers (SCLC, n = 34). Samples were analyzed by immunohistochemistry using the novel monoclonal rabbit anti-human CXCR4 antibody UMB-2 and by qRT-PCR. The expression was correlated with clinical data and overall patient survival.

Results

CXCR4 was predominantly localized at the plasma membrane of the tumor cells. CXCR4 was expressed with a high intensity in almost all of the 30 SCLC samples. In contrast, it was detected infrequently and with low intensity in the typical carcinoid and atypical carcinoid samples. There was a significant correlation between the immunohistochemistry and qRT-PCR data. Additionally, there was a significant negative relationship between CXCR4 expression and overall survival.

Conclusions

With increasing malignancy, BP-NEN clearly differ in the extent of CXCR4 expression. As in other tumor entities, CXCR4 overexpression significantly correlates with negative patient outcome. Due to its particular high expression rate in SCLC, CXCR4 may serve as a promising new target for diagnostic and pharmacological intervention as well as for peptide receptor-based radionuclide therapy.

Molecular whole-body cancer staging using positron emission tomography: consequences for therapeutic management and metabolic radiation treatment planning

A prospective analysis was performed in 124 non-small cell lung cancer patients to determine the role of F-18 fluorodeoxyglucose (FDG)-positron emission tomography (PET) for molecular (metabolic) staging (n=63), therapy monitoring after induction-chemotherapy (n=34), and conformal radiation treatment planning (n=27). Staging by FDG-PET was significantly more accurate than CT (p<0.001) and changed therapeutic management in 52% of all patients. After induction-chemotherapy, patients with complete metabolic remission histologically did not show vital tumor cells in contrast to patients with metabolic partial remission or progressive disease. Metabolic radiation treatment planning by PET led to smaller planning target volumes (PTVs) for radiation therapy (between 3% and 21% in 25/27 patients), resulting in a reduction of dose exposure to healthy tissue. In two patients, PET-PTV was larger than CT-based PTV, since PET detected lymph node metastases smaller than 1 cm. FDG-PET provides clinically important information; changes therapeutic management, can predict noninvasively effectiveness of chemotherapy, and may lead to better tumor control with less radiation-induced toxicity.

Influence of tumour size on the efficacy of targeted alpha therapy with (213)Bi-[DOTA(0),Tyr(3)]-octreotate

Background

Targeted alpha therapy has been postulated to have great potential for the treatment of small clusters of tumour cells as well as small metastases. ²¹³Bismuth, an α-emitter with a half-life of 46 min, has shown to be effective in preclinical as well as in clinical applications. In this study, we evaluated whether ²¹³Bi-[DOTA⁰, Tyr³]-octreotate (²¹³Bi-DOTATATE), a ²¹³Bi-labelled somatostatin analogue with high affinity for somatostatin receptor subtype 2 (SSTR₂), is suitable for the treatment of larger neuroendocrine tumours overexpressing SSTR₂ in comparison to its effectiveness for smaller tumours. We performed a preclinical targeted radionuclide therapy study with ²¹³Bi-DOTATATE in animals bearing tumours of different sizes (50 and 200 mm³) using two tumour models: H69 (human small cell lung carcinoma) and CA20948 (rat pancreatic tumour).

Methods

Pharmacokinetics was determined for calculation of dosimetry in organs and tumours. H69- or CA20948-xenografted mice with tumour volumes of approximately 120 mm³ were euthanized at 10, 30, 60 and 120 min post injection of a single dose of ²¹³Bi-DOTATATE (1.5–4.8 MBq). To investigate the therapeutic efficacy of ²¹³Bi-DOTATATE, xenografted H69 and CA20948 tumour-bearing mice with tumour sizes of 50 and 200 mm³ were administered daily with a therapeutic dose of ²¹³Bi-DOTATATE (0.3 nmol, 2–4 MBq) for three consecutive days. The animals were followed for 90 days after treatment. At day 90, mice were injected with 25 MBq ^99mTc-DMSA and imaged by SPECT/CT to investigate possible renal dysfunction due to ²¹³Bi-DOTATATE treatment.

Results

Higher tumour uptakes were found in CA20948 tumour-bearing animals compared to those in H69 tumour-bearing mice with the highest tumour uptake of 19.6 ± 6.6 %IA/g in CA20948 tumour-bearing animals, while for H69 tumour-bearing mice, the highest tumour uptake was found to be 9.8 ± 2.4 %IA/g. Nevertheless, as the anti-tumour effect was more pronounced in H69 tumour-bearing mice, the survival rate was higher. Furthermore, in the small tumour groups, no regrowth of tumour was found in two H69 tumour-bearing mice and in one of the CA20948 tumour-bearing mice. No renal dysfunction was observed in ²¹³Bi-DOTATATE-treated mice after the doses were applied.

Conclusions

²¹³Bi-DOTATATE demonstrated a great therapeutic effect in both small and larger tumour lesions. Higher probability for stable disease was found in animals with small tumours. ²¹³Bi-DOTATATE was effective in different neuroendocrine (H69 and CA20948) tumour models with overexpression of SSTR₂ in mice.

Electronic supplementary material

The online version of this article (doi:10.1186/s13550-016-0162-2) contains supplementary material, which is available to authorized users.

Comparison of sequential planar 177Lu-DOTA-TATE dosimetry scans with 68Ga-DOTA-TATE PET/CT images in patients with metastasized neuroendocrine tumours undergoing peptide receptor radionuclide therapy

PURPOSE

The aim of the study was to compare sequential (177)Lu-DOTA-TATE planar scans ((177)Lu-DOTA-TATE) in patients with metastasized neuroendocrine tumours (NET) acquired during peptide receptor radionuclide therapy (PRRT) for dosimetry purposes with the pre-therapeutic (68)Ga-DOTA-TATE positron emission tomography (PET)/CT ((68)Ga-DOTA-TATE) maximum intensity projection (MIP) images obtained in the same patients concerning the sensitivity of the different methods.

METHODS

A total of 44 patients (59 ± 11 years old) with biopsy-proven NET underwent (68)Ga-DOTA-TATE and (177)Lu-DOTA-TATE imaging within 7.9 ± 7.5 days between the two examinations. (177)Lu-DOTA-TATE planar images were acquired at 0.5, 2, 24, 48 and 72 h post-injection; lesions were given a score from 0 to 4 depending on the uptake of the radiopharmaceutical (0 being lowest and 4 highest). The number of tumour lesions which were identified on (177)Lu-DOTA-TATE scans (in relation to the acquisition time after injection of the therapeutic dose as well as with regard to the body region) was compared to those detected on (68)Ga-DOTA-TATE studies obtained before PRRT.

RESULTS

A total of 318 lesions were detected; 280 (88%) lesions were concordant. Among the discordant lesions, 29 were (68)Ga-DOTA-TATE positive and (177)Lu-DOTA-TATE negative, whereas 9 were (68)Ga-DOTA-TATE negative and (177)Lu-DOTA-TATE positive. The sensitivity, positive predictive value and accuracy for (177)Lu-DOTA-TATE as compared to (68)Ga-DOTA-TATE were 91, 97 and 88%, respectively. Significantly more lesions were seen on the delayed (72 h) (177)Lu-DOTA-TATE images (91%) as compared to the immediate (30 min) images (68%). The highest concordance was observed for bone metastases (97%) and the lowest for head/neck lesions (75%). Concordant lesions (n = 77; mean size 3.8 cm) were significantly larger than discordant lesions (n = 38; mean size 1.6 cm) (p < 0.05). No such significance was found for differences in maximum standardized uptake value (SUV(max)). However, concordant liver lesions with a score from 1 to 3 in the 72-h (177)Lu-DOTA-TATE scan had a lower SUV(max) (n = 23; mean 10.9) than those metastases with a score of 4 (n = 97; mean SUV(max) 18) (p < 0.05).

CONCLUSION

Although (177)Lu-DOTA-TATE planar dosimetry scans exhibited a very good sensitivity for the detection of metastases, they failed to pick up 9% of lesions seen on the (68)Ga-DOTA-TATE PET/CT. Three-dimensional dosimetry using single photon emission computed tomography/CT could be applied to investigate this issue further. Delayed (72 h) images are most suitable for drawing regions of interest for dosimetric calculations.

[Value of 18F fluorodeoxyglucose positron emission tomography in radiotherapy planning of head-neck tumors]

PURPOSE

An individualized radiation treatment planning in patients with head and neck tumors requires an exact definition of tumorspread. Despite of high reliability of methods like computed tomography, sonography or magnetic resonance imaging used in daily routine, the correct diagnosis of lymphonodal tumor infiltration is often not possible. In a prospective trial, we examined whether an additional FDG-PET gives a relevant gain of information for radiation treatment planning.

PATIENTS AND METHODS

We studied data of 34 patients with histologically confirmed squamous cell carcinoma of the head and neck who received a FDG-PET prior to treatment planning additionally to conventional staging procedures. The extent of changes of treatment strategy or target volume due to additional FDG-PET findings were analyzed.

RESULTS

In 9/22 of patients with primary tumors and in 7/12 of patients with recurrent disease, FDG-PET detected additional tumor manifestations. In all cases, changes of treatment strategy or target volume were necessary. Regarding patients with primary tumors, the percentage of treatment modifications was highest in patients with large tumors (T3 and T4) and patients with advanced lymph node involvement (N2 and N3).

CONCLUSIONS

Especially in patients with recurrent disease and patients with advanced tumor stages, FDG-PET is able to give clinically relevant information compared to conventional staging procedures. Therefore, in these group of patients a FDG-PET study prior to radiotherapy planning should be considered.

Investigating the Effect of Ligand Amount and Injected Therapeutic Activity: A Simulation Study for 177Lu-Labeled PSMA-Targeting Peptides

In molecular radiotherapy with ¹⁷⁷Lu-labeled prostate specific membrane antigen (PSMA) peptides, kidney and/or salivary glands doses limit the activity which can be administered. The aim of this work was to investigate the effect of the ligand amount and injected activity on the tumor-to-normal tissue biologically effective dose (BED) ratio for ¹⁷⁷Lu-labeled PSMA peptides. For this retrospective study, a recently developed physiologically based pharmacokinetic model was adapted for PSMA targeting peptides. General physiological parameters were taken from the literature. Individual parameters were fitted to planar gamma camera measurements (¹⁷⁷Lu-PSMA I&T) of five patients with metastasizing prostate cancer. Based on the estimated parameters, the pharmacokinetics of tumor, salivary glands, kidneys, total body and red marrow was simulated and time-integrated activity coefficients were calculated for different peptide amounts. Based on these simulations, the absorbed doses and BEDs for normal tissue and tumor were calculated for all activities leading to a maximal tolerable kidney BED of 10 Gy_2.5/cycle, a maximal salivary gland absorbed dose of 7.5 Gy/cycle and a maximal red marrow BED of 0.25 Gy₁₅/cycle. The fits yielded coefficients of determination > 0.85, acceptable relative standard errors and low parameter correlations. All estimated parameters were in a physiologically reasonable range. The amounts (for 2⁵−2⁹ nmol) and pertaining activities leading to a maximal tumor dose, considering the defined maximal tolerable doses to organs of risk, were calculated to be 272±253 nmol (452±420 μg) and 7.3±5.1 GBq. Using the actually injected amount (235±155 μg) and the same maximal tolerable doses, the potential improvement for the tumor BED was 1–3 fold. The results suggest that currently given amounts for therapy are in the appropriate order of magnitude for many lesions. However, for lesions with high binding site density or lower perfusion, optimizing the peptide amount and activity might improve the tumor-to-kidney and tumor-to-salivary glands BED ratio considerably.

Patient selection for personalized peptide receptor radionuclide therapy using Ga-68 somatostatin receptor PET/CT

Neuroendocrine tumors are malignant solid tumors originating from neuroendocrine cells dispersed throughout the body. Differentiated neuroendocrine tumors overexpress somatostatin receptors (SSTRs), which enable the diagnosis using radiolabeled somatostatin analogues. Internalization and retention within the tumor cell are important for peptide receptor radionuclide therapy using the same peptide. The use of the same DOTA-peptide for SSTR PET/CT using (68)Ga and for peptide receptor radionuclide therapy using therapeutic radionuclides like (177)Lu and (90)Y offers a unique theranostic advantage.

From Bench to Bedside-The Bad Berka Experience With First-in-Human Studies

Precision oncology is being driven by rapid advances in novel diagnostics and therapeutic interventions, with treatments targeted to the needs of individual patients on the basis of genetic, biomarker, phenotypic, or psychosocial characteristics that distinguish a given patient from other patients with similar clinical presentations. Inherent in the theranostics paradigm is the assumption that diagnostic test results can precisely determine whether an individual is likely to benefit from a specific treatment. As part and integral in the current era of precision oncology, theranostics in the context of nuclear medicine aims to identify the appropriate molecular targets in neoplasms (diagnostic tool), so that the optimal ligands and radionuclides (therapeutic tool) with favorable labeling chemistry can be selected for personalized management of a specific disease, taking into consideration the specific patient, and subsequently monitor treatment response. Over the past two decades, the use of gallium-68 labeled peptides for somatostatin receptor (SSTR)-targeted PET/CT (or PET/MRI) imaging followed by lutetium-177 and yttrium-90 labeled SSTR-agonist for peptide receptor radionuclide therapy has demonstrated remarkable success in the management of neuroendocrine neoplasms, and paved the way to other indications of theranostics. Rapid advances are being made in the development of other peptide-based radiopharmaceuticals, small molecular-weight ligands and with newer radioisotopes with more favorable kinetics, potentially useful for theranostics strategies for the clinical application. The present review features the Bad Berka experience with first-in-human studies of new radiopharmaceuticals, for example, prostate-specific membrane antigen ligand, gastrin-releasing peptide receptor, neurotensin receptor 1 ligand, novel SSTR-targeting peptides and nonpeptide, and bone-seeking radiopharmaceuticals. Also new radioisotopes, for example, actinium (²²⁵Ac), copper (⁶⁴Cu), scandium (⁴⁴Sc), and terbium (¹⁵²Tb/¹⁶¹Tb) will be discussed briefly demonstrating the development from basic science to precision oncology in the clinical setting.

Meeting report from the Prostate Cancer Foundation PSMA-directed radionuclide scientific working group

INTRODUCTION

The Prostate Cancer Foundation (PCF) convened a PSMA-Directed Radionuclide Scientific Working Group on November 14, 2017, at Weill Cornell Medicine, New York, NY.

METHODS

The meeting was attended by 35 global investigators with expertise in prostate cancer biology, radionuclide therapy, molecular imaging, prostate-specific membrane antigen (PSMA)-targeted agents, drug development, and prostate cancer clinical trials. The goal of this meeting was to discuss the potential for using PSMA-targeted radionuclide agents for the treatment of advanced prostate cancer and to define the studies and clinical trials necessary for validating and optimizing the use of these agents.

RESULTS

Several major topic areas were discussed including the overview of PSMA biology, lessons and applications of PSMA-targeted PET imaging, the nuances of designing PSMA-targeted radionuclide agents, clinical experiences with PSMA-targeted radionuclides, PCF-funded projects to accelerate PSMA-targeted radionuclide therapy, and barriers to the use of radionuclide treatments in widespread clinical practice.

DISCUSSION

This article reviews the major topics discussed at the meeting with the goal of promoting research that will validate and optimize the use of PSMA-targeted radionuclide therapies for the treatment of advanced prostate cancer.

Late results of heterotopic autotransplantation of splenic tissue into the greater omentum

There is still controversy about the beneficial effects of splenic autotransplantation. As a result, replantation of the spleen has almost been abandoned for surgical treatment of splenic injuries. To learn more about the long-term effects we have analyzed eight patients 9.2 +/- 1.2 years after autotransplantation of the spleen into the greater omentum. Splenic replants could be detected by scintigraphy in seven patients (87.5%). Splenic size, measured by single-photon emission computed tomography, varied between 19.344 and 471.705 units of volume (Uov). Two patients with the smallest replants had pathologic changes of leukocytes and lymphocyte subsets in 12 of 16 measurements (75%). These changes closely resembled a spleenless state and were similar to those in the patient with no detectable splenic autograft. In contrast, five patients with large splenic replants (49.192-471.705 UoV) revealed pathologic findings in only 2 of 40 measurements (5%). Based on an extensive review of the literature and our own results, it can be concluded that splenic autotransplantation into the greater omentum is superior to splenectomy but undoubtedly less effective than in situ preservation of the spleen. Therefore splenic replantation should still be considered, particularly in pediatric surgery, when in situ preservation of the spleen is not possible by other techniques.

Initial clinical results with technetium-99m-labeled LL2 monoclonal antibody fragment in the radioimmunodetection of B-cell lymphomas

BACKGROUND

Various monoclonal antibodies (MoAb) labeled with Iodine-131 or Indium-111 (In-111) have been investigated for radioimmunodetection of Hodgkin's and non-Hodgkin's lymphomas. Successful radioimmunotherapy also has been reported. The purpose of this pilot study was to stage non-Hodgkin's B-cell lymphomas (NHL) using whole body scintigraphy with technetium-99m (Tc-99m)-labeled murine monoclonal antibody LL2 (EPB-2) Fab' (Immunomedics, Morris Plains, NJ). Others have shown this MoAb to have specific binding to B-cell lymphomas by flow cytometry and immunofluorescence. Initial clinical studies by others have demonstrated targeting of NHL with the Tc-99m-labeled LL2-Fab'.

METHODS

One milligram of the antibody was injected intravenously after being radiolabeled with 30 mCi Tc-99m. Fifteen patients with high (n = 6), low (n = 2), and intermediate (n = 7) grade NHL were studied. No adverse effects were noted. Planar whole body imaging and single-photon emission computed tomography were performed at 2-6 h and 20-24 h postinjection. Human anti-mouse antibody levels were determined before injection and at 2 and 6 weeks.

RESULTS

In 4 of 15 patients (27%), the disease stage was altered in response to the scintigraphic findings. The physiologic biodistribution of the antibody demonstrated splenic uptake caused by antibody targeting of the white pulp and of normal B-cells, and renal uptake caused by urinary excretion. Lymph node and bone marrow involvement of known tumor sites were clearly seen. A number of previously unknown tumor sites were revealed by LL2-radioimmunodetection despite normal morphologic imaging results. Long-term follow-up of these patients is required to verify these findings. No human anti-mouse antibody elevations or adverse reactions were found in the patients studied.

CONCLUSION

These preliminary data suggest that Tc-99m-labeled LL2 Fab' yields useful clinical results, especially for the staging of patients with NHL before initial therapy or for the detection of early disease recurrence.

Antiidiotype induction therapy: evidence for the induction of immune response through the idiotype network in patients with ovarian cancer after administration of anti-CA125 murine monoclonal antibody B43.13

The immune status of ovarian cancer patients receiving anti-CA125 murine monoclonal antibody B43.13 was evaluated by measuring antiidiotypic antibodies (Ab2), antiantiidiotypic antibodies (Ab3), antiisotypic human antimouse antibodies (HAMA), interferon-gamma, and CA125 levels in the serum. A specific assay was developed for the determination of Ab2 antibodies using chimeric MAb B43.13. Of the 50 patients studied, 26 had elevated levels of Ab2. Eleven of these 26 patients also had high titer of antiantiidiotypic (Ab3) antibodies. Eight of the 22 patients analyzed had increased interferon-gamma levels. A tentative correlation was found between survival of these patients' antiidiotype induction.

Systematic comparison of sporadic and syndromic pancreatic islet cell tumors

Pancreatic islet cell tumors (ICTs) occur as sporadic neoplasias or as a manifestation of multiple endocrine neoplasia type 1 (MEN1) and von Hippel-Lindau disease (VHL). Molecular classification of ICTs is mandatory for timely diagnosis and surveillance. Systematic comparison of VHL-ICTs and sporadic ICTs has been lacking. Our registry-based approaches used the German NET-Registry with 259 patients with neuroendocrine tumors (NETs), who were primarily diagnosed with NETs, and the German VHL-Registry with 485 molecular genetically confirmed patients who had undergone magnetic resonance imaging or computed tomography of the abdomen. All patients provided blood DNA for testing of the MEN1 and VHL genes for intragenic mutations and large deletions. In the NET-Registry, 9/101 patients (8.9%) with ICTs had germline mutations, 8 in MEN1 and 1 in VHL. In the VHL-Registry, prevalence of NETs was 52/487 (10.6%), and all were ICTs. Interestingly, of those with VHL p.R167W, 47% developed ICTs, compared to 2% of those with p.Y98H. In total, there were 92 truly sporadic, i.e. mutation-negative ICT patients. Comparing these with the 53 VHL-ICT patients, the statistically significant differences were predominance of female gender (P=0.01), multifocal ICTs (P=0.0029), and lower malignancy rate (P<0.001) in VHL-ICTs compared to sporadic cases. VHL was prevalent in <0.5% of NETs, while NETs occur in ∼10% of VHL, virtually exclusively as ICTs, which are rarely the first presentation. Patients with NETs should not be subjected to genetic testing of the VHL gene, unless they have multifocal ICTs, other VHL-associated tumors, and/or a family history for VHL.

177Lu-PSMA-617 Radioligand Therapy in Metastatic Castration-Resistant Prostate Cancer Patients with a Single Functioning Kidney

The aim of this study was to assess the safety, tolerability, and effects on renal function as well as therapeutic efficacy of prostate-specific membrane antigen (PSMA)-targeted radioligand therapy (PRLT) using ¹⁷⁷Lu-labeled PSMA-617 in patients with metastatic castration-resistant prostate cancer and a single functioning kidney before PRLT. Methods: Sixteen patients (aged 53-78 y; mean age, 64.7 ± 6.5 y) with a single functioning kidney received PRLT with ¹⁷⁷Lu-PSMA-617 between March 2015 and October 2018. All parameters of renal function (serum creatinine, blood urea nitrogen, and electrolytes) were prospectively documented in a structured database and analyzed before each PRLT cycle and in follow-up. Renal function was further quantified by measuring tubular extraction rate (TER) using ^99mTc-mercaptoacetyltriglycine renal scintigraphy. Treatment-related adverse events were graded according to the Common Terminology Criteria for Adverse Events (CTCAE), version 5.0. Kaplan-Meier analysis was performed to obtain the progression-free survival and overall survival. Results: The median administered activity was 22.1 GBq (range, 15.4-33.8 GBq). The calculated absorbed radiation dose to the kidney per cycle was 5.3 ± 2.1 Gy (0.81 ± 0.32 Gy/GBq). Renal function was already impaired at baseline in 43.7% of patients, including CTCAE grade 1 renal impairment in 25.0% and CTCAE grade 2 in 18.8%. Grade 1 and 2 renal impairment, respectively, were present in 37.5% and 6.3% of the patients after the first PRLT cycle and in 31.3% and 12.5% after the second cycle. No CTCAE grade 3 or 4 nephrotoxicity was observed during or after treatment. There was no significant change in either TER or the ratio of TER to lower-limit TER after the last cycle of treatment (P > 0.05). The median PFS was 8.1 mo based on both the criteria of the European Organization for Research and Treatment of Cancer and RECIST. The median overall survival has yet to be reached with a median follow-up time of 19.3 mo (range, 5.8-45.3 mo). Conclusion: In patients with a single functioning kidney, ¹⁷⁷Lu-PSMA-617 PRLT is feasible, seems to be effective, and is well tolerated, without any signs of acute or subacute nephrotoxicity during a mean follow-up of nearly 2 y (and up to 45.3 mo). Further long-term follow-up of this special patient group is warranted.

PET with 2-[F-18]-fluoro-2-deoxy-D-glucose (FDG) in patients with cancer of unknown primary (CUP): influence on patients' diagnostic and therapeutic management

25 patients with cancer of unknown primary (CUP) were studied using PET-FDG. Whole-body-PET scans were performed based on previous morphological information. All patients underwent conventional diagnostic modalities prior to and after the PET-study. True positive results were obtained in 12/25 patients (48%) and the primary identified by PET was confirmed by further procedures. True negative results were obtained in 8/25 patients (32%) and no primary tumor was found by PET or other clinical investigations. False positive results were obtained in 5/25 patients (20%). No false negative results were obtained. In 11 patients having CT compared with PET the primary tumor was exclusively localized by PET in 8 patients (73%) and also by CT in 3 patients (27%); CT was unable to identify the tumor in 8/11 patients detected by PET. PET affected management and directed treatment in 11/25 patients (44%). The sensitivity of PET-FDG was 100%, specificity 61%. These observations demonstrate that PET-FDG is a highly sensitive method to detect CUP. Correctly classified patients in an early stage of disease may lead to benefit from a more targeted therapy with prolonged survival time. In cases of advanced disease PET might not decisively influence survival time.

Theranostics of Neuroendocrine Tumors

Somatostatin receptor positron emission tomography/computed tomography using ⁶⁸Ga-labeled somatostatin analogs is the mainstay for the evaluation of receptor status in neuroendocrine tumors (NETs). This translates towards better therapy options, with increasing evidence of peptide receptor radionuclide therapy (PRRT) as the treatment of choice for advanced or progressive NETs. There are benefits in progression-free and overall survival as well as a significant improvement in clinical condition. In patients with progressive NETs, fractionated, personalized PRRT results in good therapeutic responses with no significant severe hematological and/or renal toxicity, thus improving quality of life.

EDIM-TKTL1 blood test: a noninvasive method to detect upregulated glucose metabolism in patients with malignancies

AIM

To determine whether the TKTL1 protein epitope detection in monocytes (EDIM) test allows detection of upregulated glucose metabolism in malignancies.

MATERIALS & METHODS

The EDIM-TKTL1 blood test was conducted in 240 patients with 17 different confirmed or suspected malignancies. Test scores were compared with (18)F-fluoro-2-deoxy-D-glucose (FDG)-PET/computed tomography (CT) results.

RESULTS

EDIM-TKTL1 score and FDG-PET results showed a concordance of 90% with a sensitivity of 94% and specificity of 81%. Including CT data, all values were enhanced. A subgroup analysis of non-small-cell lung cancer patients showed a significant correlation between the EDIM-TKTL1 score and the primary tumor size determined by FDG-PET/CT.

CONCLUSION

EDIM-TKTL1 blood test revealed good concordance with FDG-PET/CT results in patients with malignancies demonstrating its efficacy to detect upregulation of glucose metabolism in primary tumors or metastases.

Alpha-peptide receptor radionuclide therapy using actinium-225 labeled somatostatin receptor agonists and antagonists

Peptide receptor radionuclide therapy (PRRT) has over the last two decades emerged as a very promising approach to treat neuroendocrine tumors (NETs) with rapidly expanding clinical applications. By chelating a radiometal to a somatostatin receptor (SSTR) ligand, radiation can be delivered to cancer cells with high precision. Unlike conventional external beam radiotherapy, PRRT utilizes primarily β or α radiation derived from nuclear decay, which causes damage to cancer cells in the immediate proximity by irreversible direct or indirect ionization of the cells' DNA, which induces apoptosis. In addition, to avoid damage to surrounding normal cells, PRRT privileges the use of radionuclides that have little penetrating and more energetic (and thus more ionizing) radiations. To date, the most frequently radioisotopes are β- emitters, particularly Yttrium-90 (90Y) and Lutetium-177 (177Lu), labeled SSTR agonists. Current development of SSTR-targeting is triggering the shift from using SSTR agonists to antagonists for PRRT. Furthermore, targeted α-particle therapy (TAT), has attracted special attention for the treatment of tumors and offers an improved therapeutic option for patients resistant to conventional treatments or even beta-irradiation treatment. Due to its short range and high linear energy transfer (LET), α-particles significantly damage the targeted cancer cells while causing minimal cytotoxicity toward surrounding normal tissue. Actinium-225 (225Ac) has been developed into potent targeting drug constructs including somatostatin-receptor-based radiopharmaceuticals and is in early clinical use against multiple neuroendocrine tumor types. In this article, we give a review of preclinical and clinical applications of 225Ac-PRRT in NETs, discuss the strengths and challenges of 225Ac complexes being used in PRRT; and envision the prospect of 225Ac-PRRT as a future alternative in the treatment of NETs.

First-In-Human Study Demonstrating Tumor-Angiogenesis by PET/CT Imaging with (68)Ga-NODAGA-THERANOST, a High-Affinity Peptidomimetic for αvβ3 Integrin Receptor Targeting

(68)Ga-NODAGA-THERANOST™ is an αvβ3 integrin antagonist and the first radiolabeled peptidomimetic to reach clinical development for targeting integrin receptors. In this first-in-human study, the feasibility of integrin receptor peptidomimetic positron emission tomography/computed tomography (PET/CT) imaging was confirmed in patients with non-small-cell lung cancer and breast cancer.

METHODS

Patients underwent PET/CT imaging with (68)Ga NODAGA-THERANOST. PET images were analyzed qualitatively and quantitatively and compared to 2-deoxy-2-((18)F) fluoro-d-glucose ((18)F-FDG) findings. Images were obtained 60 minutes postinjection of 300-500 MBq of (68)Ga-NODAGA-THERANOST.

RESULTS

(68)Ga-NODAGA-THERANOST revealed high tumor-to-background ratios (SUVmax=4.8) and uptake at neoangiogenesis sites. Reconstructed fused images distinguished cancers with high malignancy potential and enabled enhanced bone metastasis detection. (18)F-FDG-positive lung and lymph node metastases did not show uptake, indicating the absence of neovascularization.

CONCLUSIONS

(68)Ga-NODAGA-THERANOST was found to be safe and effective, exhibiting in this study rapid blood clearance, stability, rapid renal excretion, favorable biodistribution and PK/PD, low irradiation burden (μSv/MBq/μg), and convenient radiolabeling. This radioligand might enable theranostics, that is, a combination of diagnostics followed by the appropriate therapeutics, namely antiangiogenic therapy, image-guided presurgical assessment, treatment response evaluation, prediction of pathologic response, neoadjuvant-peptidomimetic-radiochemotherapy, and personalized medicine strategies. Further clinical trials evaluating (68)Ga-NODAGA-THERANOST are warranted.

Ga-68 Somatostatin Receptor PET/CT in von Hippel-Lindau Disease

Von Hippel-Lindau (VHL) disease is a dominantly inherited familial cancer syndrome with a variety of benign and malignant tumors such as retinal and central nervous system hemangioblastomas, endolymphatic sac tumors, renal cysts and tumors, pancreatic cysts and tumors, pheochromocytomas, and epididymal cystadenomas. Cross-sectional modalities (computed tomography and magnetic resonance imaging) as well as ultrasound play a major role in the initial evaluation and follow-up of the various manifestations of VHL disease. Ga-68-labeled somatostatin receptor analogs already have a significant role in the diagnosis, staging, and therapy management of neuroendocrine neoplasms and neural crest tumors. Herein, we report a case presenting a variety of malignancies in VHL and showing the usefulness of Ga-68 somatostatin receptor PET/CT as a one-stop-shop imaging modality in the management of VHL disease.