Somatostatin Receptor Expression in Lung Neuroendocrine Tumors: An Analysis of DOTATATE PET Scans.

Somatostatin receptor (SSTR) expression in metastatic lung neuroendocrine tumors (NETs) has not been well characterized using PET imaging. Understanding the degree and uniformity of SSTR expression is important to establish the role of SSTR-targeted treatments in lung NETs. Methods: A retrospective institutional review of patients with metastatic lung NETs who underwent DOTATATE PET imaging from March 2017 to February 2023 was performed. Results: In total, 48 patients with metastatic lung NETs who underwent 68Ga- or 64Cu-DOTATATE PET imaging were identified. Four had completely negative SSTR expression, and 10 had very weak expression (less than in a normal liver). Among the remaining 34 patients, 21 had uniformly positive DOTATATE PET scans, and 13 had heterogeneous expression. Only 44% had uniformly positive receptor expression, identifying them as candidates for peptide receptor radionuclide therapy. Conclusion: Most metastatic lung NETs lack uniform SSTR expression and are thus suboptimal candidates for SSTR-targeted therapy. SSTR imaging in lung NETs should be evaluated carefully for uniformity of expression.

Lymphoscintigraphy Using Tilmanocept Detects Multiple Sentinel Lymph Nodes in Melanoma Patients.

BACKGROUND: Technetium-99m-labeled Tilmanocept, a multivalent mannose, is readily internalized by the CD206 surface receptor on macrophages and dendritic cells which are abundantly present in lymph nodes. We want to examine the drainage patterns of Technetium-99m-labeled Tilmanocept to sentinel lymph nodes (SLNs) in melanoma patients following the 10% rule. METHODS: Multi-center retrospective review of patients with cutaneous melanoma undergoing SLN biopsy using Technetium-99m-labeled Tilmanocept between 2008 and 2014 was conducted. Statistical methods were used for data analyses. RESULTS: Of the 564 patients (mean age of 60.3 and 62% male) with preoperative lymphoscintigraphy showing at least one SLN, several primary tumor sites were included: 27% head/neck, 33% trunk, 21% upper extremity and 19% lower extremity. For the head/neck primary site, 36.5% of patients had multiple draining basins; for the trunk site, 36.4% of patients; for the upper extremity site, 13% of patients; and for the lower extremity, 27.4% of patients. A median of 3 (range 1-18) SLNs were identified and resected. Overall, 78% of patients had >1 SLN identified by Technetium-99m-labeled Tilmanocept. In a multivariate model, patients with >1 SLN were significantly associated with age, Breslow depth, tumor location and higher AJCC tumor stage. A total of 17.7% of patients (100/564) had a positive SLN identified. A total of 145 positive SLNs were identified out of 1,812 SLNs with a positive SLN rate of 8%. Positive SLN status was significantly associated with younger age, greater Breslow depth, mitosis rate, higher AJCC tumor stage, presence of ulceration and angiolymphatic invasion. CONCLUSIONS: Using the 10% rule, Technetium-99m-labeled Tilmanocept detects multiple SLNs in most melanoma patients.

Anatomic and Functional Imaging of Neuroendocrine Tumors.

OPINION STATEMENT: Neuroendocrine tumors (NETs) can occur in a wide variety of organs and display a spectrum of pathologic behavior. Accurate and effective imaging is paramount to the diagnosis, staging, therapy, and surveillance of patients with NET. There have been continuous advancements in the imaging of NET which includes anatomic and functional techniques.

The role of diagnostic imaging in the primary testicular cancer: initial staging, response assessment and surveillance.

Testicular cancers are a group of uncommon malignancies that account for less than 1% of new cancer cases per year in the United States and globally. The disease typically affects men between the ages of 20-44, and the overwhelming majority of tumors are germ cell in origin. Most cases of testicular cancer are organ confined at diagnosis and have a good overall prognosis. Testicular cancers are staged by the tumor, node, metastasis, serum markers (TNMS) classification set forth by the American Joint Commission on Cancer staging. Diagnostic imaging plays a crucial role in initial staging, specifically in assessing the primary tumor prior to orchiectomy and evaluating for regional and/or distant metastasis. Multimodality imaging is used for initial staging, with ultrasound and computed tomography (CT) most commonly utilized. Diagnostic imaging is also important in evaluating response in patients who initially present with metastatic disease as well as in patients who are undergoing surveillance. Typically, CT is used for response assessment and surveillance, with magnetic resonance imaging (MRI) and positron emission tomography (PET) serving as adjunct modalities. This article reviews the role of various diagnostic imaging modalities and how they are employed in the diagnosis, staging, response assessment and surveillance of primary testicular cancer.

Cardiac Metastases in Neuroendocrine Tumors: 68Ga-DOTATATE PET/CT With Cardiac Magnetic Resonance Correlation.

Neuroendocrine tumor (NET) cardiac metastases can be associated with complications including ventricular outflow obstruction, arrhythmias, heart failure, and cardiac arrest, warranting intervention. Anatomical characterization of these lesions via cardiac magnetic resonance (CMR) is helpful to assess and predict the risk of complications and guide therapy. Images of 2 patients with small bowel NET related cardiac metastases are described on Ga-DOTATATE PET/CT and CMR. The lesions were significantly smaller and more obscure on CMR compared with PET/CT. On CMR, T2-weighted dark blood images and late gadolinium enhancement images offered the most conspicuous detection of the NET myocardial metastases in these cases.

Oncologic 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography: What All Physicians Need to Know.

Fluorine-18 fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) hybrid examinations (PET/computed tomography, PET/magnetic resonance imaging) have become the most common PET imaging tools in the evaluation of the oncologic patient. Therefore it is of paramount importance that physicians who take care of oncology patients in any capacity are familiar with the basics of when these examinations are indicated, know how to best prepare the patients, and understand the benefits and limitations of the procedure. Additionally, it is important to understand which medical conditions and medications need to be controlled to maintain the diagnostic accuracy of these tests. In this article we aim to explain what 18F-FDG is, how to best prepare our patients, what PET is, and how these examinations are interpreted. Finally, we discuss some of the limitations of these examinations.

FDG avid breast cancer bone metastases silent on CT and scintigraphy: a case report with radiologic-pathologic correlation.

Bone is the one of the most common distant metastatic sites in breast cancer. Routine initial breast cancer staging evaluation typically includes computed tomography (CT) and skeletal scintigraphy while 18F fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) is reserved for clinically high-risk cases. Since FDG PET-CT is not routinely performed during staging or surveillance evaluations, it is important for radiologists and clinicians to appreciate the limitations of bone metastasis detection on CT and scintigraphy. We present a case of bony metastases of invasive ductal carcinoma of the breast which were not detected on diagnostic CT or skeletal scintigraphy but were metabolically active on FDG PET-CT and evident on magnetic resonance. We provide a review of the literature and radiologic-pathologic correlation to explain the discordant imaging findings.

Fiducial markers coupled with 3D PET/CT offer more accurate radiation treatment delivery for locally advanced esophageal cancer.

BACKGROUND AND AIMS: The role of three-dimensional positron emission tomography/computed tomography (3 D PET/CT) in esophageal tumors that move with respiration and have potential for significant mucosal inflammation is unclear. The aim of this study was to determine the correlation between gross tumor volumes derived from 3 D PET/CT and endoscopically placed fiducial markers. METHODS: This was a retrospective, IRB approved analysis of 40 patients with esophageal cancer with fiducials implanted and PET/CT. The centroid of each fiducial was identified on PET/CT images. Distance between tumor volume and fiducials was measured using axial slices. Image features were extracted and tested for pathologic response predictability. RESULTS: The median adaptively calculated threshold value of the standardized uptake value (SUV) to define the metabolic tumor volume (MTV) border was 2.50, which corresponded to a median 23 % of the maximum SUV. The median distance between the inferior fiducial centroid and MTV was - 0.60 cm (- 3.9 to 2.7 cm). The median distance between the superior fiducial centroid and MTV was 1.25 cm (- 4.2 to 6.9 cm). There was no correlation between MTV-to-fiducial distances greater than 2 cm and the gastroenterologist who performed the fiducial implantation. Eccentricity demonstrated statistically significant correlations with pathologic response. CONCLUSIONS: There was a stronger correlation between inferior fiducial location and MTV border compared to the superior extent. The etiology of the discordance superiorly is unclear, potentially representing benign secondary esophagitis, presence of malignant nodes, inflammation caused by technical aspects of the fiducial placement itself, or potential submucosal disease. Given the concordance inferiorly and the ability to more precisely set up the patient with daily image guidance matching to fiducials, it may be possible to minimize the planning tumor volume (PTV) margin in select patients, thereby, limiting dose to normal structures.

Skeletal Scintigraphy.

BACKGROUND: Skeletal scintigraphy remains a valuable tool in the initial and subsequent evaluation of the skeletal system in patients with a diagnosis of primary or metastatic neoplasms. METHODS: We discuss radiopharmaceuticals, nuclear medicine imaging techniques, and current as well as future oncological applications in the adult population. Pertinent literature was reviewed to describe the advantages and limitations of available technologies for the evaluation of skeletal metastatic disease. Evaluation of primary and metastatic skeletal disease using nuclear medicine and positron emission tomography techniques is discussed. RESULTS: Skeletal scintigraphy provides valuable information in the initial evaluation for the presence of osteoblastic skeletal metastases. Incremental advances on available radiopharmaceuticals (fludeoxyglucose F 18, sodium fluoride F 18), coupled with advances in imaging techniques and imaging devices (single photon emission computed tomography/computed tomography, positron emission tomography/computed tomography, positron emission tomography/magnetic resonance imaging), have had a significant impact on sensitivity, specificity, and accuracy rates for the detection of skeletal metastases. CONCLUSIONS: Skeletal scintigraphy has a significant role in the initial diagnosis, staging, restaging, and treatment monitoring of patients with cancer and primary skeletal or metastatic disease. The coupling of diagnostic and therapeutic nuclear medicine agents in the setting of osteoblastic skeletal metastases is a valuable tool for the treatment for certain cancer types, including prostate cancer, and may become more widely used to treat other histologies as more data on other tumor types (eg, breast cancer, osteosarcoma) become available.

Cardiac Magnetic Resonance for Evaluating Catheter Related FDG Avidity.

A 53-year-old female with a history of metastatic left arm melanoma presented for F(18) fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) which showed a moderately FDG avid focus at her port catheter tip near the cavoatrial junction. Although catheter tip related FDG avidity has previously been suggested to be bland thrombus or infection, melanoma can metastasize to unusual locations including the superior vena cava. In addition, the patient had an elevated risk of anticoagulation due to a history of hemorrhagic brain metastases. Therefore, confirmatory cardiac magnetic resonance (CMR) was obtained and findings were consistent with bland catheter-related thrombus.

Hypermetabolism on (18)F-Fluorodeoxyglucose Positron Emission Tomography Scan Does Not Influence the Interpretation of Thyroid Cytopathology, and Nodules with a SUVmax <2.5 Are Not at Increased Risk for Malignancy.

BACKGROUND: Hypermetabolism of thyroid nodules on (18)F-fluorodeoxyglucose positron emission tomography (PET) is associated with a higher prevalence of malignancy. However, the definition of hypermetabolism and its impact on cytological interpretation are unclear. METHODS: Medical records of all patients with thyroid nodules who had undergone cytological evaluation at the Moffitt Cancer Center between October 2008 and May 2014 were retrospectively reviewed. Those with a PET scan performed within one year of the cytology composed the study group, and the rest were used as controls. The distribution of the cytological categories, percentage of resection, and prevalence of malignancy among each Bethesda category was compared between both groups. RESULTS: Fifteen percent (436) of all thyroid nodules with cytological evaluation were in the study group. Maximum standardized uptake values (SUVmax) were directly associated with the probability of having a malignant or a follicular neoplasm cytological diagnosis; and inversely associated with the probability of having a benign cytological diagnosis. However, the prevalence of cancer within each Bethesda category was not associated with SUVmax values. It was found that the prevalence of malignant cytology increased to >5% with SUVmax values ≥2.5. SUVmax values were significantly higher in malignant than in benign nodules on histology (mean values 10.8 vs. 5) but with significant overlap between both groups for either the whole cohort or nodules with indeterminate cytology only limiting its use for differential diagnosis. CONCLUSIONS: The prevalence of malignancy in thyroid nodules with a SUVmax <2.5 is similar to the general population, and management should not be modified in those patients. The increased prevalence of malignancy among hypermetabolic thyroid nodules (SUVmax ≥2.5) is well characterized by cytology and does not impact the interpretation of cytological categories. Therefore, SUVmax value does not add relevant information once cytology is available.

Imaging of prostate carcinoma.

BACKGROUND: Imaging of prostate carcinoma is an important adjunct to clinical evaluation and prostate specific antigen measurement for detecting metastases and tumor recurrence. In the past, the ability to assess intraprostatic tumor was limited. METHODS: Pertinent literature was reviewed to describe the capabilities and limitations of the currently available imaging techniques for assessing prostate carcinoma. Evaluation of primary tumor and metastatic disease by ultrasonography, computed tomography (CT), magnetic resonance imaging (MRI), and nuclear medicine techniques is discussed. RESULTS: Ultrasonography and MRI have limited usefulness for local staging of prostate cancer because of suboptimal sensitivity and specificity for identifying tumor extent and capsular penetration. Additional MRI techniques such as magnetic resonance-based perfusion imaging, diffusion imaging, and spectroscopy may provide incremental benefit. CT and bone scanning provide an assessment of metastatic disease but are also limited by the poor sensitivity of lymph node size as a criterion for detecting metastases. Novel imaging techniques such as hybrid imaging devices in the form of single-photon emission CT/CT gamma cameras, positron emission tomography/CT cameras, and, in the near future, positron emission tomography/MRI combined with tumor specific imaging radiotracers may have a significant impact on tumor staging and treatment response. CONCLUSIONS: Cross-sectional imaging and scintigraphy have an important role in assessing prostate carcinoma metastases and treatment response. Increasingly, the incremental value of primary tumor imaging through MRI is being realized.

The added benefit of a dedicated neck F-18 FDG PET-CT imaging protocol in patients with suspected recurrent differentiated thyroid carcinoma.

PURPOSE: To retrospectively analyze whether adding a delayed high-resolution dedicated neck F-18 FDG positron emission tomography-computerized tomographic (PET-CT) imaging protocol in patients with recurrent differentiated thyroid cancer increases the number of abnormal foci within the neck. MATERIALS AND METHODS: Seventeen PET-CT studies from a total of 10 patients with suspected recurrent differentiated thyroid cancer between March 2003 and June 2004 were retrospectively reviewed. Each study included a whole body acquisition (WBA), followed by higher resolution dedicated neck acquisition (DNA). Two board-certified nuclear medicine physicians reviewed either the DNA or WBA for each study and recorded the number of abnormal foci, along with presence or absence of a soft tissue abnormality, and maximum standardized uptake value for each foci. Consensus review was used for all discrepancies. Statistical analysis was performed to determine whether there was a statistically significant increase in the number of studies demonstrating new abnormal foci with the addition of a DNA. RESULTS: Five of 17 studies demonstrated an increase in the number of abnormal foci with the addition of the DNA (P < 0.04). A total of 8 abnormal foci were noted on the WBA, 4 of which were within the neck. Eleven additional abnormal foci were seen on the DNA. All abnormal foci within the neck had corresponding soft tissue abnormalities except for one. CONCLUSION: Adding a higher resolution delayed DNA to the WBA for patients undergoing PET-CT imaging to detect recurrent thyroid cancer increases the number of abnormal sites of FDG accumulation.

A unique presentation of appendicitis: F-18 FDG PET/CT.

A 27-year-old white man was diagnosed with a testicular, metastatic germ cell tumor. The patient was evaluated with F-18 fluorodeoxyglucose positron emission tomography and coregistered computed tomography (FDG PET/CT) as well as a contrast-enhanced CT (CECT) of the abdomen and pelvis. Serologic tests were performed. At laparoscopic appendectomy, findings were consistent with acute suppurative appendicitis. This case exemplifies the relevance of incidental findings detected on FDG PET/CT.