Significance of 18F-Fluorodeoxyglucose Uptake at the Gastroesophageal Junction: Comparison of PET to Esophagogastroduodenoscopy

Comparative study of physiological FDG uptake in small structures between silicon photomultiplier-based PET and conventional PET

OBJECTIVE

Silicon photomultiplier-based positron emission tomography/computed tomography (SiPM-PET/CT) has the superior spatial resolution to conventional PET/CT (cPET/CT). This head-to-head comparison study compared the images of physiological 18F-fluorodeoxyglucose (FDG) accumulation in small-volume structures between SiPM-PET/CT and cPET/CT in patients scanned with both modalities, and we investigated whether the thresholds that are reported to be useful for differentiating physiological accumulations from malignant lesions can also be applied to SiPM-PET/CT.

METHODS

We enrolled 21 consecutive patients with head and neck malignancies who underwent whole-body FDG-PET/CT for initial staging or a follow-up evaluation (October 2020 to March 2022). After being injected with FDG, all patients underwent PET acquisition on both Vereos PET-CT and Gemini TF64 PET-CT systems (both Philips Healthcare) in random order. For each patient, the maximum standardized uptake value (SUVmax) was measured in the pituitary gland, esophagogastric junction (EGJ), adrenal glands, lumbar enlargement of the spinal cord, and epididymis. We measured the liver SUVmean and the blood pool SUVmean to calculate the target-to-liver ratio (TLR) and the target-to-blood ratio (TBR), respectively. Between-groups differences in each variable were examined by a paired t-test. We also investigated whether there were cases of target uptake greater than the reported threshold for distinguishing pathological from physiological accumulations.

RESULTS

Data were available for 19 patients. Ten patients were in Group 1, i.e., the patients who underwent SiPM-PET first, and the remaining nine patients who underwent cPET first were in Group 2. In the SiPM-PET results, the SUVmax of all targets was significantly higher than that obtained by cPET in all patients, and this tendency was also observed when the patients were divided into Groups 1/2. The TLRs of all targets were significantly higher in SiPM-PET than in cPET in all patients, and SiPM-PET also showed significantly higher TBRs for all targets except the EGJ (p = 0.052).

CONCLUSIONS

The physiological uptake in the small structures studied herein showed high accumulation on SiPM-PET. Our results also suggest that the thresholds reported for cPET to distinguish pathological accumulations likely lead to false-positive findings in SIPM-PET evaluations.

Clinical significance of incidental 18 FDG PET uptake in the gastrointestinal tract: a retrospective cohort study

BACKGROUND

Incidental gastrointestinal tract (GIT) uptake is found in up to 6.3% of patients undergoing positron emission tomography (PET). This may be physiologic or pathologic and requires endoscopic assessment.

AIM

To determine the diagnostic yield of endoscopy in this setting and characterise PET avidity as a predictor of clinically significant findings.

METHODS

We retrospectively reviewed all consecutive patients undergoing upper endoscopy or colonoscopy for incidental 18 FDG PET positivity in the GIT.

RESULTS

A total of 255 patients (62% male, median age 67 years) underwent colonoscopy or sigmoidoscopy for 276 separate areas of PET avidity in the colon. Malignancy was found in 44 cases (16%), and a significant polyp was found in an additional 103 cases (37%). Neoplastic change was found more often in the case of intense compared with non-intense PET avidity (odds ratio (OR) 3.40, 95% confidence interval (CI) 1.95-5.93, P < 0.001), and in focal compared with diffuse uptake (OR 5.97, 95% CI 2.9-12.2, P < 0.001). Upper GIT endoscopy was performed in 75 patients (46 male, median age 63 years) for 77 isolated areas with PET avidity. Malignancy was found in 16 cases (21%), and all were new primary lesions. Numerically, malignant findings were more common in intense (29.7%) than non-intense (12.5%) PET avidity (OR 2.96, 95%, CI 0.92-9.57, P = 0.069).

CONCLUSIONS

Both focal and intense colonic 18 FDG uptake correlate strongly with a high-risk polyp or malignant lesion. Up to 21% of all gastroscopies performed for evaluation of incidental PET uptake diagnosed a new primary malignancy. These referrals need appropriate triaging and timely endoscopic assessment.

Association of Incidental Positron Emission Tomography Uptake in the Esophagus to Gastroesophageal Reflux Disease

The Los Angeles (LA) classification is the most accurate means of assessing esophageal injury from caustic gastric acid with focused and greater concentrations in areas of erosive disease.¹ However, data from animal models and patients have proposed that an initial diffuse inflammatory pathway contributes to injury in gastroesophageal reflux disease (GERD) mediated by interleukin (IL) 8, IL1β,^2,3 and hypoxia-inducible factors.^4,5 These observations demonstrate a lymphocyte predominant inflammatory process over course of 1-2 weeks associated with basal zone hyperplasia and dilation of intercellular spaces.⁶ In cultured human esophageal epithelial cells and patients, it is further suggested that acid causes this chronic inflammatory reaction.

Candida esophagitis incidentally detected by 18F-FDG PET/CT in a patient with CNS lymphoma

Corticosteroids are commonly used in lymphoma patients, and findings in favor of esophageal involvement in 18F-FDG PET-CT should be considered suspicious and definitely be confirmed by biopsy. We describe a 58-year-old lady with diffuse large B-cell lymphoma and central nervous system involvement having an increased metabolism in the distal esophagus with 18F-FDG PET/CT, which was consistent with esophageal candidiasis, most probably due to prolonged use of dexamethasone. Esophageal candidiasis can be misdiagnosed as malignancy with a high SUVmax and may lead to difficulties while managing these patients.

Mediastinal Masses: 18F-FDG-PET/CT Features Based on the International Thymic Malignancy Interest Group Classification

Imaging plays a key role in the management of mediastinal masses. In an effort to standardize the analysis of the mediastinum, the International Thymic Malignancy Interest Group (ITMIG) has proposed a three compartments-based diagnostic classification, intended for clinicians and radiologists. Several articles have documented its usefulness to guide the diagnosis using cross-sectional imaging. Similarly, fluorine-18-radiolabeled fluorodeoxyglucose positron emission tomography combined to computed tomography (¹⁸F-FDG-PET/CT) can be useful in this setting, either as a first-line diagnostic technique, or in addition to cross-sectional imaging. In this article, which is thought as an aid for nuclear medicine physicians and radiologists, we aim to present, based on the ITMIG classification, the main mediastinal pathologies that can be observed with ¹⁸F-FDG-PET/CT, and the additional diagnostic value that can be expected from this technique. For this purpose, we segmented the mediastinum according to the ITMIG classification, and reviewed the available literature for each of the corresponding organs and/or disease. Given the importance of the clinical context for the interpretation of PET imaging, we presented each of the diseases according to: (1) their suggestive clinical context; (2) the suggestive features on nonenhanced CT (which is the standard in PET imaging); and (3) the typical ¹⁸F-FDG characteristics. The purpose of this article is to depict the main features of the most common mediastinal diseases that can be encountered with ¹⁸F-FDG-PET/CT, and to highlight its diagnostic value in this setting, alone or in combination with other imaging modalities.

Superiority of NBI endoscopy to PET/CT scan in detecting esophageal cancer among head and neck cancer patients: a retrospective cohort analysis

Background

Second primary cancer of the esophagus is frequent in head and neck patients, especially in high-risk populations, and has a great impact on the prognosis. Although Positron emission tomography (PET)/computed tomography (CT) scan is commonly conducted in head and neck patients, its ability to detect early esophageal cancer is limited. Narrow-band imaging endoscopy is an accurate and convenient technique for esophageal examination. We aimed to compare PET/CT scan and narrow-band imaging endoscopy for the detection of esophageal cancer in head and neck cancer patients.

Methods

From November 2015 to November 2018, all head and neck cancer patients who underwent both PET/CT scan and narrow-band imaging endoscopy at Changhua Christian Hospital were retrospectively enrolled. Descriptive statistics, receiver operating characteristic curve analysis, logistic regression analysis, independent Student’s t-test, and Kaplan–Meier survival analysis were conducted with MedCalc Statistical Software.

Results

A total of 147 subjects were included in the analysis; suspicious esophageal lesions were identified by PET/CT scan in 8 (5.44%) and by narrow-band imaging in 35 (23.81%). The final pathologic diagnoses were esophageal squamous cell carcinoma in 10 and high-grade dysplasia in 5. The respective sensitivity, specificity, and area under the curve for detecting suspicious esophageal lesions were 33.33, 97.73%, and 0.655 for PET/CT scan, and 100.0, 84.85%, and 0.924 for narrow-band imaging endoscopy. Hypopharyngeal or laryngeal location of the primary head and neck cancer was the only risk factor for developing second primary esophageal cancer.

Conclusions

PET/CT scan was inferior to narrow-band imaging endoscopy in detecting second primary esophageal cancer in head and neck cancer patients. In addition to PET/CT scan, narrow-band imaging endoscopy should be considered in head and neck patients at high risk for developing second primary esophageal cancer.

Evidence-based management of incidental focal uptake of fluorodeoxyglucose on PET-CT

Focal incidental uptake, with or without CT abnormalities, is a common finding on fluorodeoxyglucose PET/CT and evidence-based management for this type of uptake is lacking. This article reviews the evidence on focal incidental uptake including the incidence of malignancy, differential diagnosis and imaging criteria which can be used to further characterize it. The article focusses on PET rather than CT criteria. The strength of the evidence base is highly variable ranging from systematic reviews and meta-analyses to a virtual absence of evidence. Caution needs to be used when using standardized uptake values (SUVs) reported in other studies due to interpatient and institution observed variation in SUVs. There is sufficient evidence to permit specific suggestions on how to interpret the foci and recommend further management in the: pituitary (investigate when SUVmax >4.1), thyroid (investigate all), breast (investigate all), lung parenchyma (if focus of fluorodeoxyglucose without a CT nodule, no further investigations), colon (investigate all foci with SUVmax >5.9, urgently if SUVmax >11.4), adrenals (criteria depend on if patient has cancer) and prostate gland (investigate in males aged >50 years or >40 years if peripheral uptake or patient has other risk factors). There is some evidence to guide further management for the parotid gland, naso-orophaynx, oesophagus, pancreas, uterus and ovaries. There is insufficient evidence to guide management for the liver, spleen, kidneys, gallbladder, testis and bone, for these organs patient characteristics and other guidelines will likely be of more use in determining further management.