PET and PET/CT with 68gallium-labeled somatostatin analogues in Non GEP-NETs Tumors

Evaluation of the SSTR2-targeted Radiopharmaceutical 177Lu-DOTATATE and SSTR2-specific 68Ga-DOTATATE PET as Imaging Biomarker in Patients with Intracranial Meningioma

PURPOSE

There are no effective medical therapies for patients with meningioma who progress beyond surgical and radiotherapeutic interventions. Somatostatin receptor type 2 (SSTR2) represents a promising treatment target in meningiomas. In this multicenter, single-arm phase II clinical study (NCT03971461), the SSTR2-targeting radiopharmaceutical 177Lu-DOTATATE is evaluated for its feasibility, safety, and therapeutic efficacy in these patients.

PATIENTS AND METHODS

Adult patients with progressive intracranial meningiomas received 177Lu-DOTATATE at a dose of 7.4 GBq (200 mCi) every eight weeks for four cycles. 68Ga-DOTATATE PET-MRI was performed before and six months after the start of the treatment. The primary endpoint was progression-free survival (PFS) at 6 months (PFS-6). Secondary endpoints were safety and tolerability, overall survival (OS) at 12 months (OS-12), median PFS, and median OS.

RESULTS

Fourteen patients (female = 11, male = 3) with progressive meningiomas (WHO 1 = 3, 2 = 10, 3 = 1) were enrolled. Median age was 63.1 (range 49.7-78) years. All patients previously underwent tumor resection and at least one course of radiation. Treatment with 177Lu-DOTATATE was well tolerated. Seven patients (50%) achieved PFS-6. Best radiographic response by modified Macdonald criteria was stable disease (SD) in all seven patients. A >25% reduction in 68Ga-DOTATATE uptake (PET) was observed in five meningiomas and two patients. In one lesion, this corresponded to >50% reduction in bidirectional tumor measurements (MRI).

CONCLUSIONS

Treatment with 177Lu-DOTATATE was well tolerated. The predefined PFS-6 threshold was met in this interim analysis, thereby allowing this multicenter clinical trial to continue enrollment. 68Ga-DOTATATE PET may be a useful imaging biomarker to assess therapeutic outcome in patients with meningioma.

Management of Appendix Neuroendocrine Neoplasms: Insights on the Current Guidelines

Appendiceal neuroendocrine neoplasms (ANENs) usually present as incidental findings at the time of appendectomy for acute appendicitis. They are rare, accounting for only 0.5-1% of intestinal neoplasms; they are found in 0.3-0.9% of all appendectomy specimens. They are usually sporadic tumors. There are several histological types including well-differentiated neuroendocrine tumors (NETs), poorly differentiated neuroendocrine carcinomas (NECs), and mixed neuroendocrine-non-neuroendocrine neoplasms (MiNENs). Histologic differentiation and the grade of well-differentiated NETs correlate with clinical behavior and prognosis. Management varies based on differentiation, aggressiveness, and metastatic potential. There is debate about the optimal surgical management for localized appendiceal NETs that are impacted by many factors including the tumor size, the extent of mesoappendiceal spread, lymphovascular invasion and perineural involvement. In addition, the data to guide therapy in metastatic disease are limited due to the paucity of these tumors. Here, we review the current advances in the management of ANENs within the context of a multidisciplinary approach to these tumors.

Imaging of Neuroendocrine Prostatic Carcinoma

Neuroendocrine prostate cancer (NEPC) is an aggressive subtype of prostate cancer that typically has a high metastatic potential and poor prognosis in comparison to the adenocarcinoma subtype. Although it can arise de novo, NEPC much more commonly occurs as a mechanism of treatment resistance during therapy for conventional prostatic adenocarcinoma, the latter is also termed as castration-resistant prostate cancer (CRPC). The incidence of NEPC increases after hormonal therapy and they represent a challenge, both in the radiological and pathological diagnosis, as well as in the clinical management. This article provides a comprehensive imaging review of prostatic neuroendocrine tumors.

New Directions in Imaging Neuroendocrine Neoplasms

Purpose of Review

Accurate imaging is crucial for correct diagnosis, staging, and therapy of neuroendocrine neoplasms (NENs). The search for the optimal imaging technique has triggered rapid development in the field. This review aims at giving an overview on contemporary imaging methods and providing an outlook on current progresses.

Recent Findings

The discovery of molecular targets due to the overexpression of specific peptide hormone receptors on the NEN’s surface has triggered the development of multiple radionuclide imaging modalities. In addition to the established imaging technique of targeting somatostatin receptors, several alternative radioligands have been developed. Targeting the glucagon-like peptide-1 receptor by exendin-4 has a high sensitivity in localizing insulinomas. For dedifferentiated NENs, new molecular targets such as the C-X-C motif chemokine-receptor-4 have been evaluated. Other new targets involve the fibroblast activation protein and the cholecystokinin-2 receptors, where the ligand minigastrin opens new possibilities for the management of medullary thyroid carcinoma.

Summary

Molecular imaging is an emerging field that improves the management of NENs.

Safety, tolerability and clinical implementation of 'ready-to-use' 68gallium-DOTA0-Tyr3-octreotide (68Ga-DOTATOC) (SomaKIT TOC) for injection in patients diagnosed with gastroenteropancreatic neuroendocrine tumours (GEP-NETs)

BACKGROUND

⁶⁸Ga-DOTA0-Tyr3-octreotide (⁶⁸Ga-DOTATOC) positron emission tomography-CT (PET-CT) has superior diagnostic performance compared to the licensed tracer OctreoScan single photon emission CT-CT in patients with gastroenteropancreatic neuroendocrine tumours (GEP-NETs). A new preparation of ⁶⁸Ga-DOTATOC using a new 'ready-to-use' ⁶⁸Ga-DOTATOC formulation for injection has been developed (⁶⁸Ga-DOTATOC (SomaKIT TOC)).

OBJECTIVES

This study aimed to assess the safety and tolerability of ⁶⁸Ga-DOTATOC (SomaKIT TOC) and evaluate the feasibility and robustness of implementing it in a NET clinical imaging service.

METHODS

A first-in-human phase I/II multicentre, open-label study of a single dose of ⁶⁸Ga-DOTATOC (SomaKIT TOC) 2 MBq/kg±10% (range 100-200 MBq) in patients with biopsy-proven grade 1-2 GEP-NETs. PET-CT was performed post injection. Patients were followed up for 28 days. We next implemented this new synthesis methodology in a clinical service assessed over 11 months.

RESULTS

Twenty consenting patients were recruited; 14 males, 6 females; mean (SD) age 58 years (12); NET grade 1 (70%), grade 2 (30%); and 75% with stage IV disease. Twelve patients experienced at least one adverse event (AE) during the study with no grade 3-4 toxicities. Only four AEs were classified as possibly (headache (n=1; 4%), nausea (1; 4%)) or probably (dysgeusia (1; 4%), paraesthesia (1; 4%)) related to the study preparation. One hundred thirteen vials of ⁶⁸Ga-DOTATOC (SomaKIT TOC) were synthesised with the 'kit' over a period of 11 months for clinical utility. Only 2/113 vials (1.77%) were rejected.

CONCLUSIONS

The new ready-to-use preparation of ⁶⁸Ga-DOTATOC (SomaKIT TOC) for injection was safe and well tolerated. This has led to the world's first (EMA) licensed ⁶⁸Ga-DOTATOC (SomaKIT TOC) radiopharmaceutical for the utility of PET imaging in patients with NETs. This preparation can be robustly implemented into routine clinical practice.

Recent Advances in Nuclear Imaging of Receptor Expression to Guide Targeted Therapies in Breast Cancer

Breast cancer remains the most frequent cancer in women with different patterns of disease progression and response to treatments. The identification of specific biomarkers for different breast cancer subtypes has allowed the development of novel targeting agents for imaging and therapy. To date, patient management depends on immunohistochemistry analysis of receptor status on bioptic samples. This approach is too invasive, and in some cases, not entirely representative of the disease. Nuclear imaging using receptor tracers may provide whole-body information and detect any changes of receptor expression during disease progression. Therefore, imaging is useful to guide clinicians to select the best treatments for each patient and to evaluate early response thus reducing unnecessary therapies. In this review, we focused on the development of novel tracers that are ongoing in preclinical and/or clinical studies as promising tools to lead treatment decisions for breast cancer management.

The utility of 18F-FDG and 68Ga-DOTA-Peptide PET/CT in the evaluation of primary pulmonary carcinoid: A systematic review and meta-analysis

BACKGROUND

Pulmonary carcinoids (PC) are histologically classified into typical carcinoid (TC) and atypical carcinoid (AC). The diagnosis of pulmonary carcinoid and possibly the differentiation between TC and AC could make a significant effect on the treatment planning as well as prognosis. Several studies have explored the utility of Ga-DOTA-Peptide (Ga-labelled [1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid]-peptide) and F-flurodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) in the evaluation of primary pulmonary carcinoids. Therefore, we performed a meta-analysis to evaluate the diagnostic accuracy and prediction efficiency of histological subtypes of these two imaging modalities in primary PC.

METHODS

Relevant studies were identified by searching PubMed, Web of Science, and EMBASE published from 2006 to 2016. Two authors extracted characteristics of patients and their lesions using predefined criteria.

RESULTS

Fourteen studies comprising 352 patients were included in this meta-analysis. The pooled sensitivity of Ga-DOTA-Peptide and F-FDG PET/CT in detecting pulmonary carcinoid were 90.0% (95% CI = 82.0-95.0%; P = .07; I = 49.6%) and 71.0% (95% CI = 66.0-76.0%; P < .001; I = 59.3%), respectively. An SUVmax ratio between Ga-DOTA-Peptide and F-FDG higher than the cutoff value of 4.28 was predictive of TC with 89.3% sensitivity and 100% specificity (AUC, 96.4%; 95% CI, 91.1-100%). The ratio of tumor uptake to atelectatic lung uptake was significantly higher for Ga-DOTA-peptide (2.5-91, mean 30.5 ± 28.1) than for F-FDG (0.3-10.3, mean 2.1 ± 2.3) (P < .001).

CONCLUSIONS

Both Ga-DOTA-peptide and F-FDG are highly sensitive in detecting pulmonary carcinoid, while Ga-DOTA-peptide is more sensitive than F-FDG (90.0% vs 71.0%). The SUVmax ratio was an accurate predictor of the histopathologic variety of the carcinoid tumor, and Ga-DOTA-peptide was better than F-FDG in cases with atelectasis.

Intraindividual comparison of 68Ga-DOTATATE PET / CT vs 11C-Choline PET / CT in patients with prostate cancer in biochemical relapse: in vivo evaluation of the expression of somatostatin receptors

BACKGROUND AND OBJECTIVES

To prospectively compare the detection rate of ⁶⁸Ga-DOTATATE versus ¹¹C-choline PET/CT in patients with prostate cancer in biochemical relapse, and to evaluate somatostatin receptor expression in vivo to plan targeted therapies (¹⁷⁷Lu-DOTATATE).

MATERIAL AND METHODS

We prospectively analysed 64 patients with biochemical relapse (median PSA: 4.25 ng/mL). A PET/CT was performed with ¹¹C-choline, and another with ⁶⁸Ga-DOTATATE. The SUVmax was measured in all lesions. The correlative images, histopathology and/or clinical and biochemical follow-up were taken as the reference standard.

RESULTS

The overall detection rate per patient was 48.43% for ⁶⁸Ga-DOTATATE and 46.87% for ¹¹C-choline. The results were concordant in 53 cases (82.81%). The maximum SUV of ¹¹C-choline was significantly higher than that of ⁶⁸Ga-DOTATATE for all the concordant lesions (n=130): 6.17 (1.7-15.5) versus 4.38 (1.37-26.7), median (range) for each radiotracer, respectively (p < .0001). The sensitivity and specificity values per patient were the same for both techniques: 0.82 (0.65-0.93) and 0.9 (0.73-0.98), respectively. Although the difference was not significant, the sensitivity was lower in patients with lower PSA levels: 0.63 vs. 0.89; p=.13. A significant correlation was found between the SUVmax of both tracers (r = 0.41, n = 130, p <.0001).

CONCLUSIONS

⁶⁸Ga-DOTATATE PET/CT and ¹¹C-choline PET/CT seem to have a high capacity to detect pathological lesions in the assessment of patients with prostate cancer with biochemical relapse. Further studies are required to test the potential complementary value of these PET/CT techniques, and to evaluate the potential role of ⁸Ga-DOTATATE for planning somostatin receptor-mediated therapies (¹⁷⁷Lu-DOTATATE).

Incidental finding of a breast carcinoma on Ga-68-DOTA-1-Nal3-octreotide positron emission tomography/computed tomography performed for the evaluation of a pancreatic neuroendocrine tumor: A case report

RATIONALE

Functional imaging using radiolabeled somatostatin analogues plays an important role in the management of patients with neuroendocrine tumors, and it is a promising tool in the new era of theragnosis and personalized medicine.

PATIENTS CONCERNS

The authors present the case of a 63-year-old woman referred for evaluation of a suspected pancreatic neuroendocrine tumor by Ga-68-DOTA-1-Nal3-octreotide positron emission tomography/computed tomography (Ga-68-DOTA-NOC PET/CT).

DIAGNOSES

PET/CT confirmed increased uptake of Ga-68-DOTA-NOC in a pancreatic lesion compatible with hyperexpression of somatostatin receptors in a neuroendocrine tumor. Furthermore, PET/CT revealed increased uptake in a breast lesion and in lymphadenomegalies (less intense than in the pancreatic tumor), which conducted to the incidental diagnosis of a breast carcinoma with lymph node metastases.

INTERVENTIONS

For the breast cancer, the patient underwentneoadjuvant chemotherapy and anti-HER2 monoclonal antibody, after which she was submitted to surgery. Regarding thepancreatic neuroendocrine tumor, it was decided to maintain itunder surveillance.

OUTCOMES

Breast carcinomas are known to express somatostatin receptors and this is the first report of Ga-68-DOTA-NOC uptake in a breast tumor.

LESSONS

Ga-68-DOTA-NOC PET/CT could be useful for the management of breast cancer patients in the new era of theragnosis and personalized medicine.

Preliminary PET/CT Imaging with Somatostatin Analogs [68Ga]DOTAGA-TATE and [68Ga]DOTAGA-TOC

PURPOSE

Somatostatin receptor positron emission tomography/X-ray computed tomography (SSTR-PET/CT) is a well-established technique for staging and detection of neuroendocrine tumors (NETs). Ga-68-labeled DOTA-conjugated octreotide analogs are the privileged radiotracers for diagnosis and therapeutic monitoring of NETs. Hence, we were interested in assessing the influence of promising, newer variant DOTAGA on the hydrophilicity, pharmacokinetics, and lesion pick-up of somatostatin analogs. Herein, the potential of ([⁶⁸Ga]DOTAGA, Tyr³, Thr⁸) octreotide ([⁶⁸Ga]DOTAGA-TATE) and ([⁶⁸Ga]DOTAGA, Tyr³) octreotide ([⁶⁸Ga]DOTAGA-TOC) as NET imaging agents has been investigated.

PROCEDURES

Amenability of [⁶⁸Ga]DOTAGA-(TATE/TOC) to kit-type formulation has been demonstrated. Biodistribution studies were carried out in normal rats at 1 h post-injection (p.i.). [⁶⁸Ga]DOTAGA-(TATE/TOC) PET/CT scans were carried out in patients (70-170 MBq, 1 h p.i.) with histologically confirmed well-differentiated NETs.

RESULTS

[⁶⁸Ga]DOTAGA-TATE exhibited hydrophilicity similar to [⁶⁸Ga]DOTA-TATE (log P = -3.51 vs -3.69) whereas [⁶⁸Ga]DOTAGA-TOC was more hydrophilic than [⁶⁸Ga]DOTA-TOC (log P = -3.27 vs -2.93). [⁶⁸Ga]DOTAGA-TATE and [⁶⁸Ga]DOTA-TATE showed almost identical blood and kidney uptake in normal rats whereas significantly fast clearance (p < 0.05) of [⁶⁸Ga]DOTAGA-TATE was observed from other non-specific organs (liver, lungs, spleen, intestine). [⁶⁸Ga]DOTAGA-TOC also demonstrated rapid clearance from blood and kidneys (p < 0.05) in comparison to [⁶⁸Ga]DOTA-TOC. The metastatic lesions in NET patients were well identified by [⁶⁸Ga]DOTAGA-TATE and [⁶⁸Ga]DOTAGA-TOC.

CONCLUSION

The phenomenal analogy was observed between [⁶⁸Ga]DOTAGA-TATE and [⁶⁸Ga]DOTA-TATE as well as between [⁶⁸Ga]DOTAGA-TOC and [⁶⁸Ga]DOTA-TOC in biodistribution studies in rats. The good lesion detection ability of the two radiotracers indicates their potential as NET imaging radiotracers.

Neuroendocrine Tumor Diagnosis and Management: 68Ga-DOTATATE PET/CT

OBJECTIVE

The purpose of this article is to provide a review of the use of ⁶⁸Ga tetraazacyclododecanetetraacetic acid-DPhe1-Tyr3-octreotate (DOTATATE) PET/CT, a functional imaging modality for assessment of well-differentiated neuroendocrine tumors (NETs). It has become the preferred imaging modality for initial diagnosis, selection of patients for peptide receptor radionuclide therapy, and localization of unknown primary tumors. The National Comprehensive Cancer Network guideline has added ⁶⁸Ga-DOTATATE PET/CT as an appropriate test in the management of NETs.

CONCLUSION

In combination with FDG PET/CT, ⁶⁸Ga-DOTATATE PET/CT can noninvasively assess tumor heterogeneity, especially in G2 and G3 NETs, for personalized management of patients.

Evaluation of the Possible Utilization of 68Ga-DOTATOC in Diagnosis of Adenocarcinoma Breast Cancer

Objectives

Studies have indicated advantageous properties of [DOTA-DPhe¹, Tyr³] octreotide (DOTATOC) in tumor models and labeling with gallium. Breast cancer is the second leading cause of cancer mortality in women, and most of these cancers are often an adenocarcinoma. Due to the importance of target to non-target ratios in the efficacy of diagnosis, the pharmacokinetic of ⁶⁸Ga-DOTATOC in an adenocarcinoma breast cancer animal model was studied in this research, and the optimized time for imaging was determined.

Methods

⁶⁸Ga was obtained from ⁶⁸Ge/⁶⁸Ga generator. The complex was prepared at optimized conditions. Radiochemical purity of the complex was checked using both HPLC and ITLC methods. Biodistribution of the complex was studied in BALB/c mice bearing adenocarcinoma breast cancer. Also, PET/CT imaging was performed up to 120 min post injection.

Results

The complex was produced with radiochemical purity of greater than 98% and specific activity of about 40 GBq/mM at optimized conditions. Biodistribution of the complex was studied in BALB/c mice bearing adenocarcinoma breast cancer indicated fast blood clearance and significant uptake in the tumor. Significant tumor: blood and tumor:muscle uptake ratios were observed even at early times post-injection. PET/CT images were also confirmed the considerable accumulation of the tracer in the tumor.

Conclusion

Generally, the results proved the possible application of the radiolabelled complex for the detection of the adenocarcinoma breast cancer and according to the pharmacokenitic data, the suitable time for imaging was determined as at least 30 min after injection.

Fluoroquinolones as imaging agents for bacterial infection

Diagnosis of deep-seated bacterial infection is difficult, as neither standard anatomical imaging nor radiolabeled, autologous leukocytes distinguish sterile inflammation from infection. Two recent imaging efforts are receiving attention: (1) radioactive derivatives of sorbitol show good specificity with Gram-negative bacterial infections, and (2) success in combining anatomical and functional imaging for cancer diagnosis has rekindled interest in 99mTc-fluoroquinolone-based imaging. With the latter, computed tomography (CT) would be combined with single-photon-emission-computed tomography (SPECT) to detect 99mTc-fluoroquinolone-bacterial interactions. The present minireview provides a framework for advancing fluoroquinolone-based imaging by identifying gaps in our understanding of the process. One issue is the reliance of 99mTc labeling on the reduction of sodium pertechnetate, which can lead to colloid formation and loss of specificity. Specificity problems may be reduced by altering the quinolone structure (for example, switching from ciprofloxacin to sitafloxacin). Another issue is the uncharacterized nature of 99mTc-ciprofloxacin binding to, or sequestration in, bacteria: specific interactions with DNA gyrase, an intracellular fluoroquinolone target, are unlikely. Labeling with 68Ga rather than 99mTc enables detection by positron emission tomography, but with similar biological uncertainties. Replacing the C6-F of the fluoroquinolone with 18F provides an alternative to pertechnetate and gallium that may lead to imaging based on drug interactions with gyrase. Gyrase-based imaging requires knowledge of fluoroquinolone action, which we update. We conclude that quinolone-based probes show promise for the diagnosis of infection, but improvements in specificity and sensitivity are needed. These improvements include the optimization of the quinolone structure; such chemistry efforts can be accelerated by refining microbiological assays.

Diagnosis of Zollinger-Ellison syndrome in the era of PPIs, faulty gastrin assays, sensitive imaging and limited access to acid secretory testing

In recent years the diagnosis of Zollinger-Ellison syndrome (ZES) has become increasingly controversial with several new approaches and criteria proposed, differing from the classical biochemical criterion of inappropriate hypergastrinemia (i.e., hypergastrinemia in the presence of hyperchlorhydria) (Table 1). These changes have come about because of the difficulty and potential dangers of stopping proton pump inhibitors (PPIs) for gastric acid analysis; the recognition than many of the current assays used to assess gastrin concentrations are unreliable; the development of sensitive imaging modalities that detect neuroendocrine tumors (NETs) including an increasing number of the primary gastrinomas; the increased use of percutaneous or endoscopic ultrasound (EUS)-directed biopsies/cytology and the general lack of availability of acid secretory testing. In this article we will discuss the basis for these controversies, review the proposed changes in diagnostic approaches and make recommendations for supporting the diagnosis of ZES in the modern era.

Imaging of Neuroendocrine Tumors: Indications, Interpretations, Limits, and Pitfalls

Imaging is critical in the diagnosis, prognosis, and management of neuroendocrine tumors (NETs). NETs share common imaging features, but each type exhibits unique features. Computed tomography scans or MRI of the abdomen is used to assess tumor burden routinely. Functional imaging with octreotide scan or gallium-68 somatostatin analog PET is used selectively to confirm diagnosis and guide therapy. Clinicians and radiologists should be familiar with the indications and interpretations of imaging modalities. Novel functional imaging modalities likely will be developed to detect small NETs, predict prognosis, guide therapeutic choices, and design novel therapies.

Cushing Syndrome: Diagnostic Workup and Imaging Features, With Clinical and Pathologic Correlation

OBJECTIVE

Cushing syndrome (CS) is a constellation of clinical signs and symptoms resulting from chronic exposure to excess cortisol, either exogenous or endogenous. Exogenous CS is most commonly caused by administration of glucocorticoids. Endogenous CS is subdivided into two types: adrenocorticotropic hormone (ACTH) dependent and ACTH independent.

CONCLUSION

Cushing disease, which is caused by a pituitary adenoma, is the most common cause of ACTH-dependent CS for which pituitary MRI can be diagnostic, with bilateral inferior petrosal sinus sampling useful in equivocal cases. In ectopic ACTH production, which is usually caused by a tumor in the thorax (e.g., small cell lung carcinoma, bronchial and thymic carcinoids, or medullary thyroid carcinoma) or abdomen (e.g., gastroenteropancreatic neuroendocrine tumors or pheochromocytoma), CT, MRI, and nuclear medicine tests are used for localizing the source of ACTH. In ACTH-independent CS, which is caused by various adrenal abnormalities, adrenal protocol CT or MRI is usually diagnostic.

The significance of incidental brain uptake on 68Ga-DOTATATE PET-CT in neuroendocrine tumour patients

OBJECTIVE

Radiolabelled somatostatin analogues detect neuroendocrine tumours (NETs), but may reveal other tumour types. We examined the prevalence of possible meningioma in patients with known or suspected NETs imaged with Ga-DOTATATE PET-computed tomography (CT) on the basis of central nervous system uptake and compared with findings on magnetic resonance and contrast-enhanced CT imaging.

METHODS

Retrospective imaging reports from 313 patients who had undergone Ga-DOTATATE PET imaging for primary or repeat NET staging were searched to identify suspected meningiomas on PET. Images were then compared with findings on subsequent complementary MRI or contrast-enhanced CT scanning (performed within mean±112 days of PET-CT) if available.

RESULTS

Of 313 patients, 22 had regions of uptake suggestive of meningioma. MRI was available for 12 patients and contrast-enhanced CT was available for one patient. Of these, one patient with known von Hippel-Lindau syndrome had probable cerebellar NET metastasis. Six patient scans indicated lesions consistent with PET. Two of these reported initially did not comment on meningioma. No obvious lesion was found in the remaining six patients; however, five showed a possible correlation to venous structures. The mean maximum standardized uptake value±SEM for lesions in all 21 probable meningioma patients was 4.90±0.45.

CONCLUSION

Ga-DOTATATE is a sensitive marker of probable meningioma and may identify small lesions not reported on subsequent MRI. Lesions clearly observed on PET were identified on review in half of patients where complementary MR or CT imaging was available. Haemangioblastoma and metastatic NETs may have focal peripheral uptake similar to meningioma on Ga-DOTATATE PET and should be considered in the differential.

Unusual Cushing's Syndrome and Hypercalcitoninaemia due to a Small Cell Prostate Carcinoma

A 75-year-old man was hospitalized because of severe hypokalaemia due to ACTH dependent Cushing's syndrome. Total body computed tomography (TBCT) and 68 Gallium DOTATATE PET/CT localized a voluminous prostate tumour. A subsequent transurethral prostate biopsy documented a small cell carcinoma positive for ACTH and calcitonin and negative for prostatic specific antigen (PSA) at immunocytochemical study; serum prostatic specific antigen (PSA) was normal. Despite medical treatments, Cushing's syndrome was not controlled and the patient's clinical condition progressively worsened. Surgical resection was excluded; the patient underwent a cycle of chemotherapy followed by febrile neutropenia and fatal intestinal perforation. This case report describes a rare case of Cushing's syndrome and hypercalcitoninaemia due to a small cell carcinoma of the prostate, a rare tumour with very few therapeutic options and negative prognosis.

An Incidental Solitary Plasmacytoma of Bone Mimicking Neuroendocrine Tumor Metastasis on 68Ga-DOTATATE Positron Emission Tomography/Computed Tomography

A 54-year-old woman with suspicion of neuroendocrine tumor (NET) was referred for ⁶⁸Ga-DOTATATE positron emission tomography/computed tomography (CT) imaging due to clinical findings. A well-defined osteolytic lesion on the corpus of the third lumbar vertebra was evident on CT images with mild uptake of ⁶⁸Ga-DOTATATE, which led to suspicion of NET metastasis. Histopathologic examination revealed solitary plasmacytoma of the bone. The patient received local external radiotherapy for plasmacytoma. This case indicatesthat other diseases expressing somatostatin receptors may be inaccurately reported as tumor recurrence and highlights the importance of meticulous evaluation of positive findings.

PET/CT assessment of neuroendocrine tumors of the lung with special emphasis on bronchial carcinoids

Pulmonary neuroendocrine tumors (pNETs) arise from bronchial mucosal cells known as enterochromaffin cells which are part of the diffuse neuroendocrine system. The pathological spectrum of pNETs ranges from low-/intermediate-grade neoplasms such as bronchial carcinoids (BCs), also known as typical or atypical carcinoids, to high-grade neoplasms as large-cell neuroendocrine carcinoma and small-cell lung cancer. The tumor biology of pNETs still represents a matter of open debate. The distinct features among the different pNETs include not only their pathologic characteristics but also their clinical behavior, epidemiology, treatment, and prognosis. In this sense, a correct pathological identification in the preoperative setting is a key element for planning the best strategy of care in pNETs and especially in BCs. Controversial results have been reported on the diagnostic accuracy of fluorine-18-fluorodeoxyglucose positron emission tomography or positron emission tomography/computed tomography (F-18-FDG PET or PET/CT) in BCs. On the other hand, there is increasing evidence supporting the use of PET with somatostatin analogues (DOTA-TOC, DOTA-NOC, or DOTA-TATE) labeled with gallium-68 (Ga-68) in pNETs. Herein, we review the pertinent literature aiming to better define the current state of art of PET/CT in the detection and histological differentiation of pNETs with special emphasis on BCs.