68Ga DOTATATE PET/CT Uptake in Spinal Lesions and MRI Correlation on a Patient With Neuroendocrine Tumor: Potential Pitfalls

Unusual False Positive on 99mTc-Tektrotyd Scintigraphy Mimicking Bone Metastasis

Somatostatin receptor scintigraphy is a key diagnostic tool in the initial staging and therapeutic evaluation of neuroendocrine tumors. Its specificity can be compromised by the presence of false positives. We illustrate here the case of a vertebral hemangioma detected on 99mTc-Tektrotyd scintigraphy as an incidental finding in a 34-year-old man referred for the staging of a well-differentiated neuroendocrine tumor of the ampulla of Vater (Fig. 1).

Increased Vertebral Gallium-68-DOTATATE Activity on Positron Emission Tomography-Computed Tomography in Merkel Cell Carcinoma: Not Always Metastasis

Merkel cell carcinoma (MCC) is a rare neuroendocrine dermal malignancy seen in elderly light-skinned individuals, associated with immunosuppression and Merkel cell polyomavirus infection. As a neuroendocrine tumor, the recurrence and metastasis of MCC can be evaluated using positron emission tomography-computed tomography (PET-CT) with the Gallium-68-DOTATATE (Ga-68-DOTATATE) radiotracer, which has demonstrated increased sensitivity to neuroendocrine metastases when compared to F-18 fluorodeoxyglucose (FDG). Here, we present the case of a patient with known metastatic MCC with a new, abnormal focus of increased radiotracer activity in the thoracic spine on Ga-68-DOTATATE PET-CT suspected to represent a metastatic lesion. Further evaluation with MRI revealed a benign vertebral hemangioma, highlighting the limitations of this radiotracer in the setting of benign spinal lesions. Multimodality imaging findings of metastatic MCC and potential pitfalls of Ga-68-DOTATATE PET-CT staging are discussed.

False-Positive 68Ga-DOTATATE PET/CT Findings in Hereditary Hypophosphatemia-Osteomalacia Mimicking Culprit Lesions of Tumor-Induced Osteomalacia

⁶⁸Ga-DOTATATE PET/CT is an important imaging modality for detection of culprit lesions of tumor-induced osteomalacia in clinically symptomatic patients with hypophosphatemia-osteomalacia. Somatostatin receptor expression may at times be observed in inflammatory or granulomatous conditions and in fractures or degenerative bone disease, leading to false-positive scan findings. We present a rare case of hereditary hypophosphatemia-osteomalacia that showed increased false-positive uptake (for possible tumor-induced osteomalacia lesions) in an inflammatory condition of the maxillary sinus and a fracture of the tibia on somatostatin receptor-based ⁶⁸Ga-DOTATATE PET/CT.

Multidisciplinary management of spinal metastases: what the radiologist needs to know

The modern management of spinal metastases requires a multidisciplinary approach that includes radiation oncologists, surgeons, medical oncologists, and diagnostic and interventional radiologists. The diagnostic radiologist can play an important role in the multidisciplinary team and help guide assessment of disease and selection of appropriate therapy. The assessment of spine metastases is best performed on MRI, but imaging from other modalities is often needed. We provide a review of the clinical and imaging features that are needed by the multidisciplinary team caring for patients with spine metastases and stress the importance of the spine radiologist taking responsibility for synthesizing imaging features across multiple modalities to provide a report that advances patient care.

Current status and future of targeted peptide receptor radionuclide positron emission tomography imaging and therapy of gastroenteropancreatic-neuroendocrine tumors

Theranostics is the highly targeted molecular imaging and therapy of tumors. Targeted peptide receptor radionuclide therapy has taken the lead in demonstrating the safety and effectiveness of this molecular approach to treating cancers. Metastatic, well-differentiated gastroenteropancreatic neuroendocrine tumors may be most effectively imaged and treated with DOTATATE ligands. We review the current practice, safety, advantages, and limitations of DOTATATE based theranostics. Finally, we briefly describe the exciting new areas of development and future directions of gastroenteropancreatic neuroendocrine tumor theranostics.

68Ga-DOTATATE Uptake in an Intraosseous Hemangioma, as a Potential Cause of False-Positive PET/CT Finding, Simulating Tumoral Involvement

ABSTRACT

We present the case of a 32-year-old man with a history of hypophosphatemia and multiple bone fractures, being evaluated at our center for a potential mesenchymal tumor. 68Ga-DOTATATE PET/CT revealed a highly 68Ga-DOTATATE-avid lesion in the ethmoidal sinus extending to the nasal cavity. Following resection, histologic examination of the specimen confirmed the diagnosis of "intraosseous hemangioma," a potential cause of false-positive finding of 68Ga-DOTATATE PET/CT imaging in patients being evaluated for occult malignancies, especially at the traumatic/fractured sites.

Imaging of neuroendocrine tumors: A pictorial review of the clinical value of different imaging modalities

Neuroendocrine tumors (NETs) are multifaceted tumors occurring in a variety of organs and often present as metastatic at the time of diagnosis. Accurate staging is the most significant factor in therapy planning, but it remains a challenge. Imaging is established as the cornerstone for disease detection/diagnosis, staging, and follow up. To accurately assess and monitor tumor burden in patients with NETs, various imaging techniques have been developed and optimized. Current recommendations for the imaging of patients with NETs include a combination of both morphologic (or anatomic) and molecular imaging, but a final choice can be puzzling for clinicians. Recognizing that there is no uniform sequence consensus on the "best" imaging test, and the heterogeneity of technologic availability at different centers, we hope to provide a pictorial review of the different imaging techniques and their role and utility in management of patients with NETs, aimed to provide a practical guide for all clinicians.

An international expert opinion statement on the utility of PET/MR for imaging of skeletal metastases

BACKGROUND

MR is an important imaging modality for evaluating musculoskeletal malignancies owing to its high soft tissue contrast and its ability to acquire multiparametric information. PET provides quantitative molecular and physiologic information and is a critical tool in the diagnosis and staging of several malignancies. PET/MR, which can take advantage of its constituent modalities, is uniquely suited for evaluating skeletal metastases. We reviewed the current evidence of PET/MR in assessing for skeletal metastases and provided recommendations for its use.

METHODS

We searched for the peer reviewed literature related to the usage of PET/MR in the settings of osseous metastases. In addition, expert opinions, practices, and protocols of major research institutions performing research on PET/MR of skeletal metastases were considered.

RESULTS

Peer-reviewed published literature was included. Nuclear medicine and radiology experts, including those from 13 major PET/MR centers, shared the gained expertise on PET/MR use for evaluating skeletal metastases and contributed to a consensus expert opinion statement. [18F]-FDG and non [18F]-FDG PET/MR may provide key advantages over PET/CT in the evaluation for osseous metastases in several primary malignancies.

CONCLUSION

PET/MR should be considered for staging of malignancies where there is a high likelihood of osseous metastatic disease based on the characteristics of the primary malignancy, hight clinical suspicious and in case, where the presence of osseous metastases will have an impact on patient management. Appropriate choice of tumor-specific radiopharmaceuticals, as well as stringent adherence to PET and MR protocols, should be employed.

Small molecule drug conjugates (SMDCs): an emerging strategy for anticancer drug design and discovery

Mechanisms of how SMDCs work. Small molecule drugs are conjugated with the targeted ligand using pH sensitive linkers which allow the drug molecule to get released at lower lysosomal pH. It helps to accumulate the chemotherapeutic agents to be localized in the tumor environment upon cleaving of the pH-labile bonds.

(Radio)Theranostic Patient Management in Oncology Exemplified by Neuroendocrine Neoplasms, Prostate Cancer, and Breast Cancer

The role of nuclear medicine in the management of oncological patients has expanded during last two decades. The number of radiopharmaceuticals contributing to the realization of theranostics/radiotheranostics in the context of personalized medicine is increasing. This review is focused on the examples of targeted (radio)pharmaceuticals for the imaging and therapy of neuroendocrine neoplasms (NENs), prostate cancer, and breast cancer. These examples strongly demonstrate the tendency of nuclear medicine development towards personalized medicine.

PET/MRI for neuroendocrine tumors: a match made in heaven or just another hype?

Purpose

To evaluate the current literature on technical feasibility and diagnostic value of PET/MRI in management of patients with neuroendocrine tumors (NETs).

Methods

A systematic literature search of the PubMed/MEDLINE database identified studies that evaluated the role of simultaneous PET/MRI for the evaluation of neuroendocrine tumors in human subjects. Exclusion criteria included studies lacking simultaneous PET/MRI, absence of other than attenuation-correction MRI pulse sequences, and case reports. No data-pooling or statistical analysis was performed due to the small number of articles and heterogeneity of the methodologies.

Results

From the 21 identified articles, five were included, which demonstrated successful technical feasibility of simultaneous PET/MRI through various imaging protocols in a total of 105 patients. All articles demonstrated equal or superior detection of liver lesions by PET/MRI over PET/CT. While one study reported superior detection of bone lesions by PET/MRI, two demonstrated favorable detection by PET/CT. Two studies demonstrated superiority of PET/CT in detection of nodal metastases; three studies reported the pitfall of PET/MRI in detection of lung lesion.

Conclusion

The current literature reports successful technical feasibility of PET/MRI for imaging of NETs. While whole-body PET/CT in conjunction with an abdominal MRI may serve as a comprehensive approach for baseline staging, follow up with PET/MRI may be preferred for those with liver-only disease. Another possible role for PET/MRI is to provide a multiparametric approach to follow up of response to treatment. With further advances in MRI imaging acquisitions and post-processing techniques, PET/MRI may become more applicable to a broader group of patients with NETs, and possibly the imaging modality of choice for this patient population.

Imaging features of primary spinal osseous tumors and their value in clinical diagnosis

This study explored the method of imaging diagnosis of primary spinal osseous tumors and the application value of imaging in clinical diagnosis. Sixty-nine patients with primary spinal osseous tumors who received treatment in Nankai Hospital from July 2016 to June 2017 were selected. All of them received X-ray, computed tomography (CT) and magnetic resonance imaging (MRI) examinations to analyze the imaging features of the three examination methods. Sensitivity (Sen), specificity (Spe), positive predictive value (PV⁺), negative predictive value (PV⁻) and accuracy (Acc) were compared. The consistency of the three examination methods in diagnosing primary spinal osseous tumors was analyzed. Sen, Acc and PV⁻ of the three examination methods in diagnosing spinal osseous tumors had obvious differences. MRI showed the highest Sen (P<0.05). MRI had relatively high consistency with CT scan in diagnosing primary spinal osseous tumors, and κ-value was 0.72. CT scan and X-ray had obvious difference in diagnosing primary spinal osseous tumors (P<0.05). The consistency between CT scan and X-ray in diagnosing primary spinal osseous tumors was relatively low, and κ-value was 0.47. MRI and X-ray had obvious difference in diagnosing primary spinal osseous tumors (P<0.05). The consistency between MRI and X-ray in diagnosing primary spinal osseous tumors was relatively low, and κ-value was 0.41. X-ray examination is easy to operate with high resolution. CT scan has obvious advantages in displaying lesions with complex structure, many of which locate in overlapping sites. MRI has more advantages and higher accuracy in judging the scope of the tumor. CT and MRI examinations have obviously higher efficacy than X-ray in diagnosing primary spinal osseous tumors. They are conducive in improving the accuracy of diagnosing primary spinal osseous tumors.

ACR Practice Parameter for the Performance of Gallium-68 DOTATATE PET/CT for Neuroendocrine Tumors

Radiopharmaceuticals targeting cell surface expression of somatostatin receptors (SSTRs) are particularly useful in the evaluation of neuroendocrine tumors. Gallium-68 DOTA-Tyr-octreotatate (Ga-DOTATATE) primarily binds to SSTR type 2 receptors. Ga DOTATATE PET/CT is proven to have high impact on the management of neuroendocrine patients compared to traditional anatomical imaging as well as provides additional information over that of conventional nuclear medicine studies (indium-III DTPA-octreotide). It can result in change in management of approximately 75% of patients with neuroendocrine tumors. Ga DOTATATE and F FDG PET/CT imaging are complementary, with the degree of uptake varying depending on the degree of differentiation of the tumor. Well-differentiated tumors maintain their SSTRs and are positive on Ga DOTATATE PET/CT scan, while dedifferentiated tumors are less likely to demonstrate uptake of Ga DOTATATE but will demonstrate uptake with F FDG PET/CT. In addition, Ga DOTATATE PET/CT identifies patients with SSTR expression in their tumors, who have progressed on somatostatin analog therapy, for treatment with Lu DOTATATE.

ACR-ACNM Practice Parameter for the Performance of Fluorine-18 Fluciclovine-PET/CT for Recurrent Prostate Cancer

The American College of Radiology (ACR) and American College of Nuclear Medicine (ACNM) collaborated to develop a clinical practice document for the performance of fluciclovine positron-emission tomography (PET) / computed tomography (CT) in the evaluation of patients with suspected prostate cancer recurrence based on the elevation of prostate-specific antigen (PSA) level (biochemical recurrence) after prior therapy. Prostate cancer is the third leading cause of cancer death in the United States. Up to 50% of patients diagnosed with prostate cancer will develop biochemical failure after initial therapy. The differentiation of local from extraprostatic recurrence plays a critical role in patient management. The use of functional imaging targeting features of cancer metabolism has proven highly useful in this regard. Amino acid transport is upregulated in prostate cancer. Fluciclovine (anti-1-amino-3-F-18-fluorocyclobutane-1-carboxylic acid, FACBC, Axumin™) is an artificial amino acid PET tracer which demonstrates utility in the diagnosis of recurrent prostate cancer with significant added value to conventional imaging.

Vertebral metastases from neuroendocrine tumours: How to avoid false positives on 68Ga-DOTA-TOC PET using CT pattern analysis?

OBJECTIVES

To develop criteria to improve discrimination between vertebral metastases from neuroendocrine tumours (NETs) and benign bone lesions on PET combined with CT using DOTA-D-Phe¹-Tyr³-octreotide labelled with gallium-68 (⁶⁸Ga-DOTA-TOC).

METHODS

In 535 NET patients, ⁶⁸Ga-DOTA-TOC PET/CT examinations were reviewed retrospectively for vertebral CT lesions and/or PET foci. For each vertebral PET abnormality, appearance on CT, biological volume (BV), standardized uptake value (SUV_max) and ratios to those of reference organs were determined. All vertebral abnormalities were characterized as a metastasis, a typical vertebral haemangioma (VH) or other benign lesion.

RESULTS

In 79 patients (14.8 %), we found 107 metastases, 34 VHs and 31 other benign lesions in the spine. The optimal cut-off values to differentiate metastases from benign lesions were BV ≥0.72 cm³, SUVmax ≥2, SUVmax ratio to a reference vertebra ≥2.1, to liver ≥0.28 and to spleen ≥0.14. They corresponded to lesion-based ⁶⁸Ga-DOTA-TOC PET/CT sensitivity of 87 %, 98 %, 97 %, 99 % and 94 %, and specificity of 55 %, 100 %, 90 %, 97 %, 100 %, respectively.

CONCLUSIONS

The high sensitivity of ⁶⁸Ga-DOTA-TOC-PET/CT in detecting NET vertebral metastases was confirmed; this study showed that specificity could be improved by combining CT features and quantifying ⁶⁸Ga-DOTA-TOC uptake.

KEY POINTS

• Bone metastases in neuroendocrine tumours correlate with prognosis. • Benign bone lesions may mimic metastases on ⁶⁸ Ga-DOTA-TOC PET/CT imaging. • The specific polka-dot CT pattern may be missing in some vertebral haemangiomas. • Lesion atypical for haemangiomas can be better characterized by quantifying ⁶⁸ Ga-DOTA-TOC uptake.

68Ga-DOTATATE PET/CT Can Be an Alternative Imaging Method in Insulinoma Patients

Insulinomas are the most common cause of hypoglycemia, resulting from endogenous hyperinsulinism. The diagnosis of insulinoma is established by demonstrating inappropriately high serum insulin concentrations during a spontaneous or induced episode of hypoglycemia. Most insulinomas are islet-cell tumors. They are often small (<2 cm), benign, and difficult to localize with current imaging techniques. Insulinomas can be detected using either noninvasive procedures (e.g., transabdominal ultrasonography, spiral CT, MRI, ¹¹¹In-pentetreotide imaging, and ¹⁸F-l-dihydroxyphenylalanine PET) or invasive procedures (e.g., endoscopic ultrasonography) or a selective arterial calcium stimulation test with hepatic venous sampling. Methods: We performed ⁶⁸Ga-DOTATATE PET/CT on 3 patients with insulinoma. Results: All patients' insulinomas were shown clearly with ⁶⁸Ga-DOTATATE PET/CT. Conclusion:⁶⁸Ga-DOTATATE PET/CT imaging may be a useful noninvasive imaging technique to localize insulinomas preoperatively.

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.

Positron emission tomographic imaging of copper 64- and gallium 68-labeled chelator conjugates of the somatostatin agonist tyr3-octreotate

The bifunctional chelator and radiometal have been shown to have a direct effect on the pharmacokinetics of somatostatin receptor (SSTR)-targeted imaging agents. We evaluated three Y3-TATE analogues conjugated to NOTA-based chelators for radiolabeling with 64Cu and 68Ga for small-animal positron emission tomographic/computed tomographic (PET/CT) imaging. Two commercially available NOTA analogues, p-SCN-Bn-NOTA and NODAGA, were evaluated. The p-SCN-Bn-NOTA analogues were conjugated to Y3-TATE through β-Ala and PEG8 linkages. The NODAGA chelator was directly conjugated to Y3-TATE. The analogues labeled with 64Cu or 68Ga were analyzed in vitro for binding affinity and internalization and in vivo by PET/CT imaging, biodistribution, and Cerenkov imaging (68Ga analogues). We evaluated the effects of the radiometals, chelators, and linkers on the performance of the SSTR subtype 2--targeted imaging agents and also compared them to a previously reported agent, 64Cu-CB-TE2A-Y3-TATE. We found that the method of conjugation, particularly the length of the linkage between the chelator and the peptide, significantly impacted tumor and nontarget tissue uptake and clearance. Among the 64Cu- and 68Ga-labeled NOTA analogues, NODAGA-Y3-TATE had the most optimal in vivo behavior and was comparable to 64Cu-CB-TE2A-Y3-TATE. An advantage of NODAGA-Y3-TATE is that it allows labeling with 64Cu and 68Ga, providing a versatile PET probe for imaging SSTr subtype 2-positive tumors.

Comparison of (68)Ga DOTATATE to 18F-FDG uptake is useful in the differentiation of residual or recurrent pituitary adenoma from the remaining pituitary tissue after transsphenoidal adenomectomy

AIM

The evaluation of the remaining pituitary tissue and recurrent or residual tumor after the pituitary adenoma resection is difficult. However, it is essential to assess the size of the recurrent tumor and remaining pituitary reserve before resurgery. This study aimed to distinguish the remaining pituitary tissue from pituitary adenoma with Ga 1,4,7,10-tetraazacyclododecane-N,N',N″,N″'-tetraacetic acid-D-Phe,Tyr3-octreotate (DOTATATE) and F-FDG PET imaging in patients status post transsphenoidal adenomectomy.

METHODS

Thirty-five patients with suspected recurrent/residual pituitary tumors were retrospectively evaluated. All of these patients underwent DOTATATE and FDG PET/CT within 1 week before additional surgery. The DOTATATE and FDG uptake levels were compared. The image findings were then compared with pathology results after the additional surgery.

RESULTS

Residual or recurrent pituitary adenoma were confirmed pathologically in all 35 patients. One recurrent pituitary adenoma did not have either DOTATATE or FDG uptake. In the remaining 34 adenomas, 33 had higher FDG uptake than DOTATATE uptake. In comparison, DOTATATE had significant higher uptake than FDG in the remaining pituitary tissues in all cases.

CONCLUSIONS

Different degree of uptake of Ga DOTATATE and F-FDG PET/CT in the remaining pituitary tissue and recurrent/residual pituitary tumor indicated that combined analysis of Ga DOTATATE and F-FDG PET/CT might be of clinical value in differentiating recurrent/residual pituitary adenoma from the remaining pituitary tissue.