Intraoperative Gamma Probe Detection of Head and Neck Paragangliomas with 111In-Pentetreotide: A Pilot Study

Theranostic strategies in sarcoma: preliminary clinical evidence

INTRODUCTION

Sarcomas encompass a highly diverse range of malignancies, characterized by varied morphological and molecular profiles. Treatment options in case of therapy-refractory or advanced disease are limited. In this context, theranostics emerges as an innovative platform seamlessly integrating diagnosis and therapy, offering promising prospects.

AREAS COVERED

This special report delves into the initial clinical applications of theranostic-based approaches in sarcomas. Specifically, it examines various strategies targeting biomarkers associated with sarcomas, including fibroblast activation protein (FAP), prostate-specific membrane antigen (PSMA), C-X-C chemokine receptor type 4 (CXCR4) and somatostatin receptor 2 (SSTR2).

EXPERT OPINION

The heterogeneous uptake of the CXCR4-targeted radioligand in lesions, along with its poor correlation with immunohistochemistry data, diminishes the attractiveness of this theranostic approach in the sarcoma oncological setting. SSTR2-targeted approaches in sarcoma, although potentially effective, are limited to a single case. Early experiences with FAP inhibitors in sarcoma patients have shown particularly promising outcomes, indicating effective disease control with minimal toxicity. While PSMA presents an enticing target for theranostic approaches in sarcomas, its utilization remains anecdotal and requires further investigation. Prospective and well-designed clinical trials are imperative to delineate the potential impact of FAPI- and PSMA-based approaches on sarcoma therapeutic landscapes, offering innovative and personalized treatment options.

PARP-Targeted Radiotheranostics with Auger Electrons: An Updated Overview

Auger electrons (AEs) represent an intriguing topic in the field of radionuclide therapy. They are emitted by several radionuclides commonly used in nuclear medicine (indium-111, iodine-123, iodine-125), allowing for highly localized energy deposition and thus exerting a radiotoxic effect on specific cellular and sub-cellular targets. However, due to their short range in matter, AEs have had limited use in therapeutic applications so far. In recent years, the synthesis of various radiopharmaceuticals capable of binding to the enzyme poly(ADP-ribose) polymerase 1 has reignited interest in this type of therapy, laying the groundwork for a theranostic approach based on radionuclides emitting AEs. The enzyme PARP-1 operates enzymatically in close proximity to DNA that represents the prime target of radionuclide therapies. Following this trend, several PARP-targeted radiopharmaceuticals for AE-based theranostics have been developed. We provide an updated overview of preclinical studies focused on the applications of this new theranostic approach in glioblastoma, breast, prostate and ovarian carcinoma, and pancreatic adenocarcinoma.

Radio-Guided Lung Surgery: A Feasible Approach for a Cancer Precision Medicine

BACKGROUND

Radio-guided surgery is a reliable approach used for localizing ground-glass opacities, lung nodules, and metastatic lymph nodes. Lung nodules, lymph node metastatic involvement, and ground-glass opacities often represent a challenge for surgical management and clinical work-up.

METHODS

PubMed research was conducted from January 1997 to June 2023 using the keywords "radioguided surgery and lung cancer".

RESULTS

Different studies were conducted with different tracers: technetium-99m-albumin macroaggregates, cyanoacrylate combined to technetium-99m-sulfur colloid, indium-111-pentetreotide, and fluorine-18-deoxyglucose. A study proposed naphthalocyanine radio-labeled with copper-64. Radio-guided surgery has been demonstrated to be a reliable approach in localizing a lesion, and has a low radiological burden for personnel exposure and low morbidity. The lack of necessity to conduct radio-guided surgery under fluoroscopy or echography makes this radio-guided surgery an easy way of performing precise surgical procedures.

CONCLUSIONS

Radio-guided surgery is a feasible approach useful for the intraoperative localization of ground-glass opacities, lung nodules, and metastatic lymph nodes. It is a valid alternative to the existing approaches due to its low cost, associated low morbidity, the possibility to perform the procedure after several hours, the low radiation dose applied, and the small amount of time that is required to perform it.

Gastrin-releasing peptide receptor agonists and antagonists for molecular imaging of breast and prostate cancer: from pre-clinical studies to translational perspectives

INTRODUCTION

Prostate and breast cancer represent a leading cause of cancer-related death worldwide with a dramatic social and demographic impact. Gastrin-releasing peptide receptors (GRPRs), part of the bombesin (BBN) family, have been found overexpressed in both the aforementioned malignancies, and have emerged as a potentially useful target to combine imaging and therapy in a unique, synergistic approach, namely 'theranostics.'

AREAS COVERED

The biological characteristics of GRPRs, as well as their aberrant expression in breast and prostate cancer, are covered. Furthermore, the role of the different available GRPR agonists and antagonists, labeled with radionuclides suitable for molecular imaging through single photon computed tomography (SPECT) or positron emission computed (PET/CT), is reviewed, with a particular focus on the potential theranostic implications.

EXPERT OPINION

GRPR-targeted molecular imaging of breast and prostate cancer gave promising results in pre-clinical studies. Notably, GRPRs' expression was found to be inversely correlated with disease progression in both prostate and breast cancer. Among the different GRPR agonists and antagonists applied as imaging probes, RM26 presented particularly interesting applications, with meaningful theranostic potential, but its diagnostic performance resulted highly influenced by the choice of the chelator-radionuclide complex, being long-life radionuclides more suitable for obtaining high-contrast imaging.

Prostate-specific membrane antigen-directed imaging and radioguided surgery with single-photon emission computed tomography: state of the art and future outlook

INTRODUCTION

Prostate-specific membrane antigen (PSMA) has emerged as a highly relevant target for prostate cancer (PC) diagnosis and therapy. PSMA inhibitors targeting PSMA-enzymatic domain have been successfully labeled with radionuclides emitting positrons or gamma-photons, thus obtaining tracers suitable for imaging with positron emission computed tomography (PET/CT) or single-photon emission tomography (SPECT).

AREAS COVERED

The different approaches for obtaining PSMA-ligands labeled with gamma-emitting nuclides (^99mTc or¹¹¹In) are reviewed. Furthermore, the applications of ^99mTc/¹¹¹In-PSMA SPECT for the imaging of PC patients in different clinical settings (staging or biochemical recurrence) are covered. Lastly, the employment of PSMA-targeted SPECT tracers for radioguided surgery (RGS) during primary or salvage lymphadenectomy is discussed.

EXPERT OPINION

RGS provided satisfying preliminary results in both primary and salvage lymphadenectomy, allowing to discriminate between pathological and non-pathological nodes with high accuracy, although prospective studies with larger cohorts are needed to further validate this surgical approach. The potential of PSMA-targeted SPECT/CT has not been fully explored yet, but it might represent a relatively cost-effective alternative to PSMA PET/CT in limited resource environments. In this perspective, the implementation of novel SPECT technologies or algorithms, such as semiconductor-ionization detectors or resolution recovery reconstruction, will be topic of future investigation.

Somatostatin Receptor Targeted PET-Imaging for Diagnosis, Radiotherapy Planning and Theranostics of Meningiomas: A Systematic Review of the Literature

The aims of the present systematic review are to: (1) assess the diagnostic performance of somatostatin receptor (SSR)targeted positron emission tomography (PET) with different tracers and devices in patients affected by meningiomas; and (2) to evaluate the theranostic applications of peptide receptor radionuclide therapy (PRRT) in meningiomas. A systematic literature search according to PRISMA criteria was made by using two main databases. Only studies published from 2011 up to March 2022 in the English language with ≥10 enrolled patients were selected. Following our research strategy, 17 studies were included for the assessment. Fourteen studies encompassed 534 patients, harboring 733 meningiomas, submitted to SSR-targeted PET/CT (n = 10) or PET/MRI (n = 4) for de novo diagnosis, recurrence detection, or radiation therapy (RT) planning (endpoint 1), while 3 studies included 69 patients with therapy-refractory meningiomas submitted to PRRT (endpoint 2). A relevant variation in methodology was registered among diagnostic studies, since only a minority of them reported histopathology as a reference standard. PET, especially when performed through PET/MRI, resulted particularly useful for the detection of meningiomas located in the skull base (SB) or next to the falx cerebri, significantly influencing RT planning. As far as it concerns PRRT studies, stable disease was obtained in the 66.6% of the treated patients, being grade 1–2 hematological toxicity the most common side effect. Of note, the wide range of the administered activities, the various utilized radiopharmaceuticals (⁹⁰Y-DOTATOC and/or ¹⁷⁷Lu-DOTATATE), the lack of dosimetric studies hamper a clear definition of PRRT potential on meningiomas’ management.

The Role and Potential of 18F-FDG PET/CT in Malignant Melanoma: Prognostication, Monitoring Response to Targeted and Immunotherapy, and Radiomics

Novel therapeutic approaches, consisting of immune check-point inhibitors (ICIs) and molecularly targeted therapy, have thoroughly changed the clinical management of malignant melanoma (MM), the most frequent and deadly skin cancer. Since only 30-40% of MM patients respond to ICIs, imaging biomarkers suitable for the pre-therapeutic stratification and response assessment are warmly welcome. In this scenario, positron emission computed tomography (PET/CT) with 18F-fluorodeoxyglucose (18F-FDG) has been successfully utilized for advanced MM staging and therapy response evaluation. Furthermore, several PET-derived parameters (SUVmax, MTV, TLG) were particularly impactful for the prognostic evaluation of patients submitted to targeted and immunotherapy. In this review, we performed a web-based and desktop research on the clinical applications of 18F-FDG PET/CT in MM, with a particular emphasis on the various metabolic criteria developed for interpreting PET/CT scan in patients undergoing immunotherapy or targeted therapy or a combination of both. Furthermore, the emerging role of radiomics, a quantitative approach to medical imaging applying analysis methodology derived by the field of artificial intelligence, was examined in the peculiar context, putting a particular emphasis on the potential of this discipline to support clinicians in the delicate process of building patient-tailored pathways of care.

The North American Neuroendocrine Tumor Society Consensus Guidelines for Surveillance and Management of Metastatic and/or Unresectable Pheochromocytoma and Paraganglioma

ABSTRACT

This manuscript is the result of the North American Neuroendocrine Tumor Society consensus conference on the medical management and surveillance of metastatic and unresectable pheochromocytoma and paraganglioma held on October 2 and 3, 2019. The panelists consisted of endocrinologists, medical oncologists, surgeons, radiologists/nuclear medicine physicians, nephrologists, pathologists, and radiation oncologists. The panelists performed a literature review on a series of questions regarding the medical management of metastatic and unresectable pheochromocytoma and paraganglioma as well as questions regarding surveillance after resection. The panelists voted on controversial topics, and final recommendations were sent to all panel members for final approval.

Aptamer-based technology for radionuclide targeted imaging and therapy: a promising weapon against cancer

INTRODUCTION

aptamers are short artificial, single-strand oligonucleotide sequences (DNA, RNA or modified RNA), capable of binding to biological molecules with high affinity and specificity. Due to their relatively low cost of production and scarce immunogenicity, many efforts have been made to produce aptamers directed against specific molecular targets, such as receptors or transporters overexpressed by malignancies.

AREAS COVERED

the technological approaches for generating aptamers are reviewed. Furthermore, the applications of radiolabeled aptamers for the in vivo imaging of several oncological biomarkers through single photon emission computed tomography (SPECT) or positron emission tomography (PET), are covered. Lastly, targeted therapy based on the utilization of aptamers labeled with radionuclides emitting beta particles is discussed, with particular emphasis to the oncological perspectives.

EXPERT OPINION

The main limitation of radiolabeled aptamers is represented by their in vivo sensitivity to endogenous nuclease, so that several strategies have been developed to increase the stability of these compounds. Although the applications of aptamers are still in a preliminary and pre-clinical phase, it is reasonable to hypothesize that this technology will play a major role for personalized medicine in the next years.

Molecular and Metabolic Imaging of Hepatic Neuroendocrine Tumors Following Radioembolization with 90Y-microspheres

Liver is the predominant site of metastatization for neuroendocrine tumors (NETs). Up to 75% of patients affected by intestinal NETs present liver metastases at diagnosis. For hepatic NET, surgery represents the most effective approach but is often unfeasible due to the massive involvement of multifocal disease. In such cases, chemotherapy, peptide receptor radionuclide therapy and loco-regional treatments may represent alternative therapeutic options. In particular, radioembolization with 90Y-microspheres has been introduced as a novel technique for treating hepatic malignant lesions, combining the principles of embolization and radiation therapy. In order to evaluate the response to 90Y-radioembolization, standard radiologic criteria have been demonstrated to present several limitations. 18Fluoro-deoxyglucose (FDG) Positron Emission Tomography (PET) is routinely used for monitoring the response to therapy in oncology. Nevertheless, NETs often present low glycolytic activity thus the conventional 18FDG PET may not be adequate for these tumors. For many years, somatostatin receptor scintigraphy (SRS) with 111In-pentetreotide has been used for diagnosis and staging of NETs. More recently, three 68Ga-DOTA-compounds have been developed and introduced for the imaging of NETs with PET technology. The aim of the present paper was to review the existing literature concerning the application of different metabolic and molecular probes for the imaging evaluation of hepatic NETs following 90Y-RE.

Theragnostic Aspects and Radioimmunotherapy in Pediatric Tumors

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

Theranostic approaches in nuclear medicine: current status and future prospects

Introduction: Theranostics is an emerging field in which diagnosis and specific targeted therapy are combined to achieve a personalized treatment approach to the patient. In nuclear medicine clinical practice, theranostics is often performed utilizing the same molecule labeled with two different radionuclides, one radionuclide for imaging and another for therapy.Areas covered: The authors review the clinical applications of different radiopharmaceuticals in the field of interest, including the well-established use of radioactive iodine in differentiated thyroid cancer, radiolabeled metaiodobenzylguanidine (MIBG) in neuroblastoma and the clinical impact of peptide radionuclide receptorial therapy (PRRT) in the management of neuroendocrine tumors. Furthermore, the more cutting-edge and recently introduced theranostic approaches will be reviewed, such as the radioligand therapy with ¹⁷⁷Lu-prostate specific membrane antigen (PSMA) and targeted alpha therapy in castration-resistant prostate cancer. Finally, the main applications of PET for the imaging of biomarkers suitable for the non-radionuclide targeted therapy will be covered.Expert opinion: Theranostics is envisaging a revolutionary clinical approach which is deeply connected with the concept of personalized medicine and ruled by a 'patient-centered' vision. In this perspective, the theranostic applications will need well-trained specialists, capable to manage not only the technological aspects of the discipline, but also to deal with the more innovative oncological therapies in a multidisciplinary setting.

Molecular Imaging in Pediatric Brain Tumors

In the last decade, several radiopharmaceuticals have been developed and investigated for imaging in vivo of pediatric brain tumors with the aim of exploring peculiar metabolic processes as glucose consumption, amino-acid metabolism, and protein synthesis with nuclear medicine techniques. Although the clinical shreds of evidence are limited, preliminary results are encouraging. In this review, we performed web-based and desktop research summarizing the most relevant findings of the literature published to date on this topic. Particular attention was given to the wide spectrum of nuclear medicine advances and trends in pediatric neurooncology and neurosurgery. Furthermore, the role of somatostatin receptor imaging through single-photon emission computed tomography (SPECT) and positron emission tomography (PET) probes, with reference to their potential therapeutic implications, was examined in the peculiar context. Preliminary results show that functional imaging in pediatric brain tumors might lead to significant improvements in terms of diagnostic accuracy and it could be of help in the management of the disease.

Somatostatin receptor expression in non-classical locations - clinical relevance?

In-111 pentetreotide (Octreoscan) is a radiolabeled somatostatin analog with high binding affinity to somatostatin receptors (SSTR) used in somatostatin receptor scintigraphy (SRS). Pentetreotide labelled with In-111 is widely used due to its high affinity to SSTR 2 and 5. SSTR are expressed on neuroendocrine cells as well as several non-neural and non-endocrine cells with varying levels of density. We retrospectively reviewed articles and publications related to octreoscan accumulation in sites that classically do not have high concentrations of SSTR as well as in organs and tissues from diseases which are not usually diagnosed by octreoscan. The significance of a positive uptake as assessed by octreoscan in non-somatostatin receptor related diseases is not fully understood yet. Localization of octreotide in non-oncological disease states such as inflammation is due to presence of SSTR in activated immunological cells, over-expression by activated cells in the respective tissue and SSTR expression by blood vessels. In granulomatous diseases, over-expression of SSTR2 preferential binding sites were detected in epitheloid and giant cells. The purpose of the current study is to identify octreoscan localization in non-somatostatin receptor related disease sites to better understand the mechanism of this nonspecific accumulation which may help expand the clinical utilization of functional imaging utilizing somatostatin receptor scintigraphy in diagnosis and perhaps therapy.

Radioguided exploration facilitates surgical cytoreduction of neuroendocrine tumors

INTRODUCTION

Radioguided exploration (RGS) can be an important tool to direct the cytoreduction of neuroendocrine tumors (NETs). The selection of the proper radiolabeled isotope, the dose, and the time interval between isotope injection and exploration are the major factors that lead to the successful use of this technique.

METHODS

Data on 43 patients who underwent RGS of their NET at our facility (Ochsner Medical Center-Kenner) was collected. These cases were reviewed to determine the optimal radiopharmaceutical, dose, and interval between injection and exploration.

RESULTS

The isotopes used were (99)technetium sulfur colloid in three patients, (123)I metaiodobenzylguanidine ((123)I-MIBG) in six patients, and (111)In-pentreotide in 30 abdominal NET patients and in four patients undergoing neck and mediastinum explorations. In 29 of 30 (111)In-pentreotide-guided abdominal explorations (five of which were re-explorations, all successful), the gamma detector was determined to be "helpful". In the four neck and mediastinum explorations, the gamma probe was deemed "essential" for completing a quick, safe, and minimally invasive procedure. (123)I-MIBG injection, in contrast, was useful in only one patient. The optimal dose and interval between injection and exploration of (111)In-pentreotide were discovered to be 6 mCi injected 7 days prior to the planned exploration.

CONCLUSION

Radioguided exploration is a useful tool to guide the cytoreduction of NETs. The correct choice of radiopharmaceutical, its dose, and the interval between injection and exploration are critical for obtaining optimal results.

Carotid body tumors: radioguided surgical approach

Background

Carotid body tumours (CBTs) are very rare lesions which should be treated as soon as possible even when benign since small tumour size permits easier removal and lower incidence of perioperative complications and recurrence. Malignant forms are rare and they can be identified by lymph node invasion and metastases in distant locations. The need of reliable and effective diagnostic modalities for both primary CBTs and its metastases or recurrence is evident.

The present study reviews our experience and attempt to define the role of colour coded ultrasound (CCU) and Somatostatin receptor scintigraphy (SRS) with Indium-111-DTPA-pentetretide (Octreoscan^®) using both planar and single photon emission tomography (SPECT) technique in the diagnosis and follow-up of these uncommon lesions within a multidisciplinary approach.

Methods

From 1997 to 2008, 12 patients suffering from 16 CBTs (4 bilateral) were investigated by CCU and SRS-SPECT before and after surgery. All tumours were grouped according to Shamblin's classification in order to assess the technical difficulties and morbidity of surgical resection on the ground of their size and relationship with the carotid arteries. Intraoperative radiocaptation by Octreoscan^®) was also carried out in all cases to evaluate the radicality of surgery. All perioperative scans were evaluated by the same nuclear medicine physician.

Results

Preoperatively CCU showed CBTs (four were not palpable) with a sensitivity of 100%. Radioisotope imaging identified the CBTs as chemodectomas in 15 cases while no radioisotopic uptake was detected in 1 vagus nerve neurinoma. No evidence of metastasis or multicentricity were seen by total body radioisotopic scans. Combined data from CCU and SRS-SPECT allowed to determine tumour size in order to select 7 larger tumours which were submitted to selective preoperative embolization.

Intraoperatively Octreoscan demonstrated microscopic tumour leftovers promptly removed in 1 case and an unresectable remnant at the base of the skull in another case.

During follow-up CCI and radioisotope scans showed no recurrence in 14 cases and a slightly enlargement of the intracranial residual as detected during surgery in 1 patient.

Conclusion

CCU may allow an early and noninvasive detection of CBTs and hence safer operations. The combined use of CCU and SRS-SPECT provide useful data to identify those tumours and to evaluate their extent and carotid arteries infiltration. Radioisotope imaging is a sensitive modality to detect metastases and lymph node involvement that are markers of CBT malignancy. After surgery CCU and SRS-SPECT can be accurate modalities for surveillance for an early detection of CBTs recurrence.

Radio-guided neurosurgery (RGNS): early experience with its use in brain tumour surgery

DEFINITION

Radio Guided Neurosurgery(1) (RGNS) is a technique using systemic administration of radionuclide in which a gamma probe is used intra-operatively to identify isotope-rich brain tumour, and check for residual lesions after excision of visually identifiable lesion.

AIMS

To assess the usefulness of this technique in surface-localizing brain tumours, in real time, intra-operative identification of tumour from brain, and in assessing completeness of excision. Tumours in or near eloquent areas are of special interest.

SETTINGS AND DESIGN

Prospective, non-randomized and non-blinded.

METHODS AND MATERIAL

The study included 19 patients with intrinsic brain tumours operated between July 2005 & December 2006. A high degree of radioisotope uptake was confirmed on Single Positron Emission Computed Tomography (SPECT) with fusion of Computed Tomographic (CT) images (SPECT-CT) in all patients after IV injections of 99m Technetium Sestamibi (Tc). We use a Euro 4 Probe (Euro Medical Instruments, Paris) which detects gamma emissions. Intra-operatively, the probe was used to identify tumour from normal brain using a difference in activity of a factor of 2. The end point was complete tumour removal as determined by absence of significant residual activity.

RESULTS AND CONCLUSIONS

This inexpensive and highly portable system provides realtime, intra-operative identification of tumour and assessment of completeness of tumour excision. It can guide the location of craniotomy and identify visually indistinct tumor from normal brain, a situation where the surgeon may leave behind residual tumour to avoid serious deficits. The use of RGNS enhances the neurosurgeon's confidence with tumours in or near eloquent areas and provides reliable proof of the completeness of excision in real time.

Gamma probes and their use in tumor detection in colorectal cancer

The purpose of this article is to summarize the role of gamma probes in intraoperative tumor detection in patients with colorectal cancer (CRC), as well as provide basic information about the physical and practical characteristics of the gamma probes, and the radiopharmaceuticals used in gamma probe tumor detection. In a significant portion of these studies, radiolabeled monoclonal antibodies (Mabs), particularly 125I labeled B72.3 Mab that binds to the TAG-72 antigen, have been used to target tumor. Studies have reported that intraoperative gamma probe radioimmunodetection helps surgeons to localize primary tumor, clearly delineate its resection margins and provide immediate intraoperative staging. Studies also have emphasized the value of intraoperative gamma probe radioimmunodetection in defining the extent of tumor recurrence and finding sub-clinical occult tumors which would assure the surgeons that they have completely removed the tumor burden. However, intraoperative gamma probe radioimmunodetection has not been widely adapted among surgeons because of some constraints associated with this technique. The main difficulty with this technique is the long period of waiting time between Mab injection and surgery. The technique is also laborious and costly. In recent years, Fluorine-18-2-fluoro-2-deoxy-D-glucose (18F-FDG) use in gamma probe tumor detection surgery has renewed interest among surgeons. Preliminary studies during surgery have demonstrated that use of FDG in gamma probe tumor detection during surgery is feasible and useful.

Carotid body tumors: advantages of contrast ultrasound investigation

Carotid body tumors are rare neoplasms that have to be considered in the evaluation of all lateral neck mass. Early surgical removal has been recommended to avoid possible cranial nerve injury, the most common perioperative complication. Computed tomography (CT) and magnetic resonance imaging (MRA) angiographies are the preferred pre-operative diagnostic imaging investigations, as well as the 111 In-pentetreotide scintigraphic scan, whereas the standard ultrasound investigations have poor sensitivity in characterizing of the blood flows of the parenchimal structure of the carotid body tumors. We describe a case of a patient with a carotid body tumor assessed with contrast ultrasonography that clearly improved the quality of the standard color Duplex. This technique may represent a non-invasive method, easy to use and to repeat, and able to achieve high diagnostic accuracy.

Prospective comparison of two gamma probes for intraoperative detection of 18F-FDG: in vitro assessment and clinical evaluation in differentiated thyroid cancer patients with iodine-negative recurrence

PURPOSE

This study was aimed at evaluating the spatial resolution and sensitivity of two hand-held gamma probes. Radioguided surgery was tested in seven patients with iodine-negative differentiated thyroid cancer (DTC) recurrence using (18)F-FDG PET.

METHODS

Two gamma probes were evaluated: Clerad's GammaSup with a collimated CsI(Tl) scintillator and Novelec's Modelo2 with a BGO scintillator. Five measurement tests were performed following the NEMA guidelines (NU3-2004). Radioguided surgery was performed in patients with recurrent DTC and abnormal (18)F-FDG uptake on preoperative (18)F-FDG PET images. Patients were injected with rTSH 2 days before surgery. A mean activity of 211 MBq of (18)F-FDG was injected 60 min before surgery. In vivo and ex vivo counts were recorded for suspected tumours and normal tissue.

RESULTS

Spatial resolution was higher with the CsI(Tl) than with the BGO detector: 20.2-40.6 mm vs 20.6-55.3 mm from 0 to 20 mm depth. Sensitivity in air and water and through side shielding was higher for BGO but the signal-to-noise ratio was 88 and 22 with the BGO compared to 131 and 76 with the CsI(Tl) at 10 and 30 mm depth. Median in vivo SNR (tumour/non-tumour ratio) was 1.8 with both the BGO and the CsI(Tl) detector, while ex vivo ratios of 2.3 and 2.1, respectively, were obtained. Radioguided surgery allowed detection of all of the tumours identified by (18)F-FDG PET images.

CONCLUSION

This study demonstrated the feasibility of high-energy photon detection with a conventional scintillator equipped with a collimator. The CsI(TI) probe detected more true events from background than did the BGO detector during surgery.

Ectopic Cushing' syndrome caused by a neuroendocrine carcinoma of the mesentery

Background

ACTH overproduction within the pituitary gland or ectopically leads to hypercortisolism. Here, we report the first case of Cushing' syndrome caused by an ectopic ACTH-secreting neuroendocrine carcinoma of the mesentery. Moreover, diagnostic procedures and pitfalls associated with ectopic ACTH-secreting tumors are demonstrated and discussed.

Case presentation

A 41 year-old man presented with clinical features and biochemical tests suggestive of ectopic Cushing's syndrome. First, subtotal thyroidectomy was performed without remission of hypercortisolism, because an octreotide scan showed increased activity in the left thyroid gland and an ultrasound revealed nodules in both thyroid lobes one of which was autonomous. In addition, the patient had a 3 mm hypoenhancing lesion of the neurohypophysis and a 1 cm large adrenal tumor. Surgical removal of the pituitary lesion within the posterior lobe did not improve hypercortisolism and we continued to treat the patient with metyrapone to block cortisol production. At 18-months follow-up from initial presentation, we detected an ACTH-producing neuroendocrine carcinoma of the mesentery by using a combination of octreotide scan, computed tomography scan, and positron emission tomography. Intraoperatively, use of a gamma probe after administration of radiolabeled ¹¹¹In-pentetreotide helped identify the mesenteric neuroendocrine tumor. After removal of this carcinoma, the patient improved clinically. Laboratory testing confirmed remission of hypercortisolism. An octreotide scan 7 months after surgery showed normal results.

Conclusion

This case underscores the diagnostic challenge in identifying an ectopic ACTH-producing tumor and the pluripotency of cells, in this case of mesenteric cells that can start producing and secreting ACTH. It thereby helps elucidate the pathogenesis of neuroendocrine tumors. This case also suggests that patients with ectopic Cushing's syndrome and an octreotide scan positive in atypical locations may benefit from explorative radioguided surgery using ¹¹¹In-pentetreotide and a gamma probe.