FDG-PET and CT characterization of adrenal lesions in cancer patients

Role of 18F-fluorodeoxyglucose positron-emission tomography/computed tomography in restaging of adrenocortical carcinoma

Background

The objective was to retrospectively evaluate the contribution of fluorodeoxyglucose [18F] positron emission tomography/computed tomography (18FDG-PET/CT) to the re-staging of adrenocortical carcinoma (ACC).

Materials and methods

A total of 16 patients (10 males and 6 females), who underwent adrenalectomy due to adrenocortical carcinoma and 18FDG-PET/CT scan to re-stage the tumor between July 2007 and April 2013, were included in the present study. The mean age was 53.37 ± 13.91 years (min: 30, max: 74) The patients were required to fast for six hours prior to scanning, and whole-body PET scanning from the skull base to the upper thighs was performed approximately 1 h after the intravenous injection of 555 MBq of F-18 FDG. Whole body CT scanning was performed in the cranio-caudal direction. FDG-PET images were reconstructed using CT data for attenuation correction. Suspicious recurrent or metastatic lesions were confirmed by histopathology or clinical follow-up.

Results

Sensitivity, specificity, positive predictive value, negative predictive value and accuracy of 18FDG-PET/CT were 100%, 83.3%, 90.9%, 83.3%, and 93.7%, respectively.

Conclusion

18FDG-PET/CT detects local recurrence and/or distant metastases with high accuracy in the re-staging of operated adrenocortical carcinoma. It is considered that the procedure could play an important role in treatment decision after the operation and post-operative follow-up and could influence the entire decision-making process.

Analysis of discordant PET and CT findings in 18F-FDG PET-CT scans in the management of oncology patients

BACKGROUND

Discordant findings are often noted between PET-CT and CT images of 18F-FDG PET-CT scans and cause ambiguity in image interpretation.This study aimed at determining the significance of these findings in the management of oncology patients.

CONTEXT

Discordant findings are often noted between PET-CT and CT images of 18F-FDG PET-CT scans and cause ambiguity in image interpretation.

AIM

This study aimed at determining the significance of these findings in the management of oncology patients.

METHODS

This was an observational, descriptive study. Hence, retrospective analysis of all discordant findings in oncology patients undergoing a PETCT imaging between Jan 2013 and Jan 2016 was done. Those patients who had a follow-up period of minimum 1 year in either of the following forms - repeat PETCT imaging, other radiological imaging, clinical, or histopathological evidence were included. From all the discordant lesions, the sensitivity, specificity, positive predictive, negative predictive value, and accuracy of both PET-CT and CT modalities were determined.

RESULTS

Of 348 discordant lesions, 16.7% was noted in soft tissues, 25% in viscera, 28.7% in lungs, 14.1% in lymph nodes, and 15.5% in bones. At the end of follow-up, 15.2% lesions were PET true positive, 57.5% PET true negative, 10.1% CT true positive lesions, 13.8% CT true negative, and 3.4% were inconclusive.

CONCLUSION

18F-FDG PET-CT is superior to CT imaging and should be considered as the first-line imaging modality in oncology patients.

18F-FDG-PET/CT-based machine learning model evaluates indeterminate adrenal nodules in patients with extra-adrenal malignancies

BACKGROUND

To assess the value of an 18F-FDG-positron emission tomography/computed tomography (PET/CT)-based machine learning model for distinguishing between adrenal benign nodules (ABNs) and adrenal metastases (AMs) in patients with indeterminate adrenal nodules and extra-adrenal malignancies.

METHODS

A total of 303 patients who underwent 18F-FDG-PET/CT with indeterminate adrenal nodules and extra-adrenal malignancies from March 2015 to June 2021 were included in this retrospective study (training dataset (n = 182): AMs (n = 97), ABNs (n = 85); testing dataset (n = 121): AMs (n = 68), ABNs (n = 55)). The clinical and PET/CT imaging features of the two groups were analyzed. The predictive model and simplified scoring system for distinguishing between AMs and ABNs were built based on clinical and PET/CT risk factors using multivariable logistic regression in the training cohort. The performances of the predictive model and simplified scoring system in both the training and testing cohorts were evaluated by the areas under the receiver operating characteristic curves (AUCs) and calibration curves. The comparison of AUCs was evaluated by the DeLong test.

RESULTS

The predictive model included four risk factors: sex, the ratio of the maximum standardized uptake value (SUVmax) of adrenal lesions to the mean liver standardized uptake value, the value on unenhanced CT (CTU), and the clinical stage of extra-adrenal malignancies. The model achieved an AUC of 0.936 with a specificity, sensitivity and accuracy of 0.918, 0.835, and 0.874 in the training dataset, respectively, while it yielded an AUC of 0.931 with a specificity, sensitivity, and accuracy of 1.00, 0.735, and 0.851 in the testing dataset, respectively. The simplified scoring system had comparable diagnostic value to the predictive model in both the training (AUC 0.938, sensitivity: 0.825, specificity 0.953, accuracy 0.885; P = 0.5733) and testing (AUC 0.931, sensitivity 0.735, specificity 1.000, accuracy 0.851; P = 1.00) datasets.

CONCLUSIONS

Our study showed the potential ability of a machine learning model and a simplified scoring system based on clinical and 18F-FDG-PET/CT imaging features to predict AMs in patients with indeterminate adrenal nodules and extra-adrenal malignancies. The simplified scoring system is simple, convenient, and easy to popularize.

Adrenal findings in FDG-PET: analysis of a cohort of 1021 patients from a cancer center

PURPOSE

The use of FDG-PET for cancer staging has led to the increasing incidence of adrenal lesions, which are usually a clinical challenge. We aimed to characterize the adrenal lesions found in FDG-PET of patients followed in a cancer center.

METHODS

Retrospective analysis was conducted of all FDG-PET studies performed in our center in the last 10 years. Exams reporting adrenal lesions in the CT component and/or anomalous adrenal FDG uptake were selected. Cases were characterized by the clinical, laboratory, imaging, and pathological findings.

RESULTS

We identified 27,427 FDG-PET studies. Of those, 7.6% reported adrenal findings. We included 1364 exams corresponding to 1021 patients. Only 15.6% of the patients were referred to the Endocrinology Department and 38% of the lesions were not studied. In 38.9% of the studied patients, malignant lesions were present, including metastases in 37.5%, carcinoma in 1.2%, and other malignant tumors in 0.4%. The median SUVmax of malignant lesions was significantly higher than the SUVmax of the benign findings (p < 0.05). We also observed a higher median SUVmax in adrenal metastases than in adenomas (p < 0.05). There was a tendency for higher SUVmax of adrenal carcinomas when compared with other malignant lesions (p = 0.066). The median SUVmax was not different between pheochromocytomas and other tumors (p > 0.05).

CONCLUSION

Occult adrenal lesions discovered during FDG-PET/CT are common in the cancer context and are frequently benign. SUVmax may be a useful tool in the workup of adrenal lesions but with several important caveats.

Pearls and pitfalls in lung cancer staging

Lung cancer is the third most common cancer in the UK and is the leading cause of death. Radiology plays a central role in the diagnostic work-up of patients with suspected and known lung cancer. Tumour assessment includes both local staging, as well as distant staging. Local staging objectives include the assessment of technical resectability with regard to the evaluation of tumour size and invasion of surrounding structures. Distant staging objectives aim to identify distant metastasis in lymphatic and extra lymphatic tissues. CT, positron emission tomography/CT, MRI, and ultrasound are routinely used imaging techniques for staging in patients with lung cancer. In this review, we will consider the pitfalls of these examinations that radiologists potentially face during the work-up of patients with lung cancer.

Predicting malignancy in patients with adrenal tumors using 18 F-FDG-PET/CT SUVmax

BACKGROUND AND OBJECTIVES

¹⁸ F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸ F-FDG-PET/CT) parameters may help distinguish malignant from benign adrenal tumors, but few have been externally validated or determined based on definitive pathological confirmation. We determined and validated a threshold for ¹⁸ F-FDG-PET/CT maximum standard uptake value (SUVmax) in patients who underwent adrenalectomy for a nonfunctional tumor.

METHODS

Database review identified patients with ¹⁸ F-FDG-PET/CT images available (training cohort), or only SUVmax values (validation cohort). Discriminative accuracy was assessed by area under the curve (AUC), and the optimal cutoff value estimated by maximally selected Wilcoxon rank statistics.

RESULTS

Of identified patients (n = 171), 86 had adrenal metastases, 20 adrenal cortical carcinoma, and 27 adrenal cortical adenoma. In the training cohort (n = 96), SUVmax was significantly higher in malignant versus benign tumors (median 8.3 vs. 3.0, p < .001), with an AUC of 0.857. Tumor size did not differ. The optimal cutoff SUVmax was 4.6 (p < .01). In the validation cohort (n = 75), this cutoff had a sensitivity of 75% and specificity 55%.

CONCLUSIONS

¹⁸ F-FDG-PET/CT SUVmax was associated with malignancy. Validation indicated that SUVmax ≥ 4.6 was suggestive of malignancy, while lower values did not reliably predict benign tumor.

EUS-B-FNA for Left Adrenal Lesions in Non-Small Cell Lung Cancer Patients: Report of Cases and Literature Review

The left adrenal gland (LAG) is a common metastatic site in patients with non-small-cell lung cancer. In practice, staging mainly relies on radiologic studies and endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA). Recently, a new technique using convex probe-endobronchial ultrasound (CP-EBUS) scope through the esophagus (EUS-B) has been introduced. A complete mediastinal staging and a reach for upper-abdominal structures in a single session naturally attract attention. However, scientific data are not sufficient to clearly judge the role of this technique in the cytological diagnosis of left adrenal lesions. Therefore, we present cases in which our patients have undergone EUS-B for LAG lesions to increase the data in the literature with regard to accessibility, diagnostic performance, and rate of complications.

Adrenal Oncocytoma: An Incidental Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography Findings with Magnetic Resonance Imaging Correlation

A good percentage of adrenal masses in patients with known malignancy may be benign; thus, noninvasive characterization is important in preventing unnecessary biopsy. This case report represents a patient with papillary thyroid carcinoma and known lung metastasis for which she was followed up with whole-body fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) postradioactive iodine therapy. During the follow-up, she had developed an adrenal mass lesion seen by FDG PET/CT and further characterized by magnetic resonance imaging (MRI). This case demonstrates the potential importance of combining the molecular characterization by FDG PET/CT with the data derived from MRI in narrowing the differential diagnosis of an adrenal mass and suggesting the next diagnostic step in reaching the definitive diagnosis.

Practical Approach to Adrenal Imaging

Various pathologies can affect the adrenal gland. Noninvasive cross-sectional imaging is used for evaluating adrenal masses. Accurate diagnosis of adrenal lesions is critical, especially in cancer patients; the presence of adrenal metastasis changes prognosis and treatment. Characterization of adrenal lesions predominantly relies on morphologic and physiologic features to enable correct diagnosis and management. Key diagnostic features to differentiate benign and malignant adrenal lesions include presence/absence of intracytoplasmic lipid, fat cells, hemorrhage, calcification, or necrosis and locoregional and distant disease; enhancement pattern and washout values; and lesion size and stability. This article reviews a spectrum of adrenal pathologies.

Diagnostic performance of unenhanced computed tomography and 18 F-fluorodeoxyglucose positron emission tomography in indeterminate adrenal tumours

OBJECTIVE

Evidence on the diagnostic performance of adrenal imaging is limited. We aimed to assess the diagnostic performance of unenhanced computed tomography (CT) and ¹⁸ F-fluorodeoxyglucose (¹⁸ FDG) positron emission tomography (PET)/CT imaging in a high-risk population for adrenal malignancy using an optimal reference standard.

DESIGN

Retrospective cohort study.

METHODS

Imaging studies of patients with adrenal nodules who underwent adrenal biopsy and/or adrenalectomy between 1994 and 2014 were reviewed and compared to the reference standard of histology. Eighty % of patients presented with known or suspected extra-adrenal malignancy.

RESULTS

Unenhanced abdominal CT was performed in 353 patients with adrenal lesions; median size was 3 (0.7-15) cm and median radiodensity was 33 (-21-78) Hounsfield units (HU). Radiodensity of >10 HU diagnosed malignancy with a sensitivity of 100%, specificity of 33%, positive predictive value (PPV) of 72% and negative predictive value (NPV) of 100%. ¹⁸ FDG-PET/CT was performed in 89 patients; median tumour size was 2.1 (0.7-9.2) cm. Maximum standardized uptake (SUV max) was higher in malignant lesions when compared to benign lesions (median=10 [2.3-29.4] vs 3.7 [1.4-24.5], respectively, P<.0001). Similarly, median SUV max lesion to SUV max liver ratio (ALR) in malignant lesions was higher than in benign lesions (median=3 [0.74-13.4] vs 1.2 [0.5-6.6], respectively, P<.0001). ¹⁸ FDG-PET/CT ALR >1.8 diagnosed malignancy with a sensitivity of 87%, specificity of 84%, PPV of 85% and NPV of 86%.

CONCLUSION

Noncontract CT radiodensity of ≤10 HU excludes malignancy even in a high-risk population. For indeterminate adrenal lesions, given a superior specificity, ¹⁸ FDG-PET/CT could be considered as a second stage imaging study.

Adrenal Imaging

Cross-sectional imaging can make a specific diagnosis in lesions, such as myelolipomas, cysts, and hemorrhage, and is often sufficient to distinguish benign from malignant adrenal processes. CT and MRI are useful studies to identify pheochromocytomas and cortisol-secreting or androgen-secreting tumors. In patients with primary aldosteronism, adrenal venous sampling remains the most accurate localizing study and should be performed in all patients older than 35. Radiolabeled isotope studies serve as second-line diagnostic tests for malignant adrenal tumors, primary or metastatic, as well as for pheochromocytoma. Nuclear imaging studies should follow a robust hormonal diagnosis and be correlated with findings on cross-sectional imaging.

Adrenocortical neoplasms in adulthood and childhood: distinct presentation. Review of the clinical, pathological and imaging characteristics

Adrenocortical tumors (ACT) in adulthood and childhood vary in clinical, histopathological, molecular, prognostic, and imaging aspects. ACT are relatively common in adults, as adenomas are often found incidentally on imaging. ACT are rare in children, though they have a significantly higher prevalence in the south and southeast regions of Brazil. In clinical manifestation, adults with ACT present more frequently with glucocorticoid overproduction (Cushing syndrome), mineralocorticoid syndromes (Conn syndrome), or the excess of androgens in women. Subclinical tumors are frequently diagnosed late, associated with compression symptoms of abdominal mass. In children, the usual presentation is the virilizing syndrome or virilizing association and hypercortisolism. Histopathological grading and ACT classification in malignant and benign lesions are different for adults and children. In adults, the described criteria are the Hough, Weiss, modified Weiss, and Van Slooten. These scores are not valid for children; there are other criteria, such as proposed by Wieneke and colleagues. In molecular terms, there is also a difference related to genetic alterations found in these two populations. This review discusses the imaging findings of ACT, aiming to characterize the present differences between ACT found in adults and children. We listed several differences between magnetic resonance imaging (MRI), computed tomography (CT), and positron emission tomography-computed (PET-CT) and also performed a literature review, which focuses on studied age groups of published articles in the last 10 years regarding cortical neoplasm and imaging techniques. Published studies on ACT imaging in children are rare. It is important to stress that the majority of publications related to the differentiation of malignant and benign tumors are based almost exclusively on studies in adults. A minority of articles, however, studied adults and children together, which may not be appropriate.

EUS-B-FNA vs conventional EUS-FNA for left adrenal gland analysis in lung cancer patients

INTRODUCTION

In patients with lung cancer, left adrenal glands (LAG) suspected for distant metastases (M1b) based on imaging require further evaluation for a definitive diagnosis. Tissue acquisition is regularly performed using conventional EUS-FNA. The aim of this study was to investigate the success rate of endoscopic ultrasound guided fine-needle aspiration using the EBUS scope (EUS-B-FNA) for LAG analysis.

METHODS

This is a prospective multicenter study in consecutive patients with (suspected) lung cancer and suspected mediastinal and LAG metastases. Following complete mediastinal staging using the EBUS scope (EBUS+EUS-B), the LAG was evaluated and sampled by both EUS-B (experimental procedure) and conventional EUS (current standard of care).

RESULTS

The success rate for LAG analysis (visualized, sampled and adequate tissue obtained) was 89% (39/44; 95% CI 76-95%) for EUS-B-FNA, and 93% (41/44; 95%CI 82-98%) for EUS-FNA. In the absence of metastases at EUS-B and/or EUS, surgical verification of the LAG or 6 months clinical and radiological follow-up was obtained, but missing for 5 patients. The prevalence of LAG metastases was 54% (21/39). In patients in whom LAG was seen and sampled, sensitivity for LAG metastases was at least 87% (95%CI 65-97%) for EUS-B, and at least 83% (95%CI 62-95%) for conventional EUS.

CONCLUSION

LAG analysis by EUS-B shows a similar high success rate in comparison to conventional EUS.

IMPLICATION

Both a mediastinal nodal and LAG evaluation can be adequately performed with just an EBUS scope and single endoscopist. This staging strategy is likely to reduce patient-burden and costs.

Diagnostic performance of 18-F-FDG-PET-CT in adrenal lesions using histopathology as reference standard

PURPOSE

To determine the diagnostic performance of PET-CT in differentiating benign and malignant adrenal lesions when evaluating PET parameters individually as well as in combination with CT parameters, using histopathology as the reference standard.

METHODS

¹⁸F-FDG-PET-CT scans of patients undertaken within 6 months prior to pathologic evaluation of their adrenal lesion(s) were evaluated. PET assessments consisted individually of maximum standardized uptake value of the adrenal lesion (A-SUV_max) and its ("normalized") ratio to the liver (R-SUV_max). The diagnostic performances of these two PET parameters were also assessed when combined with the Hounsfield density from the non-contrast CT component of the PET-CT (A-HU). Diagnostic performance was assessed by area under the curve (AUC) of the receiver operating characteristics. Multiple logistic regression analysis was used to evaluate the individual and combined parameters.

RESULTS

The study cohort consisted of 61 adrenal lesions (59 patients). Malignant lesions (n = 52) had significantly higher median PET and CT parameters than benign lesions: A-SUV_max (11.4 vs. 6.1), R-SUV_max (3.3 vs. 1.7), and A-HU (37 vs. 24) [all p < 0.023]. AUC for the PET parameters individually was almost identical: 0.75 for A-SUV_max and 0.74 for R-SUV_max. On univariate analysis, thresholds of A-SUV_max >3.47 and R-SUV_max >0.83 yielded maximum accuracy (both 87%). The combination of these PET parameters individually with A-HU improved both AUC and accuracy (0.81% and 93%, respectively).

CONCLUSIONS

The individual PET parameters A-SUV_max and R-SUV_max have similar diagnostic performance for differentiating malignant and benign adrenal lesions; their performance and accuracy improve when combined with the CT component (A-HU).

Practical Approach to Adrenal Imaging

Various pathologies can affect the adrenal gland. Noninvasive cross-sectional imaging is used for evaluating adrenal masses. Accurate diagnosis of adrenal lesions is critical, especially in cancer patients; the presence of adrenal metastasis changes prognosis and treatment. Characterization of adrenal lesions predominantly relies on morphologic and physiologic features to enable correct diagnosis and management. Key diagnostic features to differentiate benign and malignant adrenal lesions include presence/absence of intracytoplasmic lipid, fat cells, hemorrhage, calcification, or necrosis and locoregional and distant disease; enhancement pattern and washout values; and lesion size and stability. This article reviews a spectrum of adrenal pathologies.

Laparoscopic adrenalectomy for solitary adrenal metastasis from lung cancer

BACKGROUND AND OBJECTIVES

Several studies have been reported on the problem of determining when laparoscopic adrenalectomy is indicated for solitary adrenal metastasis of malignant tumors. Our efforts at answering this question constitute the basis of this report.

METHODS

From June 2010 to June 2011, laparoscopic adrenalectomy was performed in 10 lung cancer patients with solitary adrenal metastases (5 adenocarcinomas, 1 squamous cell carcinoma, 1 large cell carcinoma, 1 small cell carcinoma, and 2 pleomorphic carcinomas). The surgical results of all 10 patients were examined.

RESULTS

Adrenal swelling was detected by computed tomography in all patients except 1 case of pleomorphic carcinoma. The findings of positron emission tomography-computed tomography were positive in 8 patients, including the 2 cases with pleomorphic carcinomas. Laparoscopic surgery was successfully performed in 9 cases. In the eighth patient (a case of pleomorphic carcinoma with adrenal swelling), laparoscopic adrenalectomy was attempted but conversion to open surgery was required because of clear evidence of pancreatic invasion.

CONCLUSION

The results obtained in this study, along with other published reports, support 4 criteria as operative indications for laparoscopic adrenalectomy in solitary adrenal metastasis from the lung: (1) the primary lung cancer is resected or can be cured by radical chemotherapy, (2) metastasis is limited to the adrenal gland only, (3) adrenal metastasis does not invade the surrounding organs, and (4) the size of the adrenal tumor does not exceed 10 cm. In cases of pleomorphic carcinoma, laparoscopic adrenalectomy should be performed when positron emission tomography-computed tomography results are positive.

Current generation time-of-flight (18)F-FDG PET/CT provides higher SUVs for normal adrenal glands, while maintaining an accurate characterization of benign and malignant glands

OBJECTIVE

Modern PET/CT scanners have significantly improved detectors and fast time-of-flight (TOF) performance and this may improve clinical performance. The aim of this study was to analyze the impact of a current generation TOF PET/CT scanner on standardized uptake values (SUV), lesion-background contrast and characterization of the adrenal glands in patients with suspected lung cancer, in comparison with literature data and commonly used SUV cut-off levels.

METHODS

We included 149 adrenal glands from 88 patients with suspected lung cancer, who underwent (18)F-FDG PET/CT. We measured the SUVmax in the adrenal gland and compared this with liver SUVmean to calculate the adrenal-to-liver ratio (AL ratio). Results were compared with literature derived with older scanners, with SUVmax values of 1.0 and 1.8 for normal glands [1, 2]. Final diagnosis was based on histological proof or follow-up imaging. We proposed cut-off values for optimal separation of benign from malignant glands.

RESULTS

In 127 benign and 22 malignant adrenal glands, SUVmax values were 2.3 ± 0.7 (mean ± SD) and 7.8 ± 3.2 respectively (p < 0.01). Corresponding AL ratios were 1.0 ± 0.3 and 3.5 ± 1.4 respectively (p < 0.01). With a SUVmax cut-off value of 3.7, 96% sensitivity and 96% specificity was reached. An AL ratio cut-off value of 1.8 resulted in 91% sensitivity and 97% specificity. The ability of both SUVmax and AL ratio to separate benign from malignant glands was similar (AUC 0.989 vs. 0.993, p = 0.22).

CONCLUSIONS

Compared with literature based on the previous generation of PET scanners, current generation TOF (18)F-FDG PET/CT imaging provides higher SUVs for benign adrenal glands, while it maintains a highly accurate distinction between benign and malignant glands. Clinical implementation of current generation TOF PET/CT requires not only the use of higher cut-off levels but also visual adaptation by PET readers.

Metabolic and anatomic characteristics of benign and malignant adrenal masses on positron emission tomography/computed tomography: a review of literature

PET/CT with (18)F-fluorodeoxyglucose (FDG) or using different radiocompounds has proven accuracy for detection of adrenal metastases in patients undergoing cancer staging. It can assist the diagnostic work-up in oncology patients by identifying distant metastases to the adrenal(s) and defining oligometastatic disease that may benefit from targeted intervention. In patients with incidentally discovered adrenal nodules, so-called adrenal "incidentaloma" FDG PET/CT is emerging as a useful test to distinguish benign from malignant etiology. Current published evidence suggests a role for FDG PET/CT in assessing the malignant potential of an adrenal lesion that has been 'indeterminately' categorized with unenhanced CT, adrenal protocol contrast-enhanced CT, or chemical-shift MRI. FDG PET/CT could be used to stratify patients with higher risk of malignancy for surgical intervention, while recommending surveillance for adrenal masses with low malignant potential. There are caveats for interpretation of the metabolic activity of an adrenal nodule on PET/CT that may lead to false-positive and false-negative interpretation. Adrenal lesions represent a wide spectrum of etiologies, and the typical appearances on PET/CT are still being described, therefore our goal was to summarize the current diagnostic strategies for evaluation of adrenal lesions and present metabolic and anatomic appearances of common and uncommon adrenal lesions. In spite of the emerging role of PET/CT to differentiate benign from malignant adrenal mass, especially in difficult cases, it should be emphasized that PET/CT is not needed for most patients and that many diagnostic problems can be resolved by CT and/or MR imaging.

Adrenal imaging (Part 1): Imaging techniques and primary cortical lesions

Adrenal glands can be affected by a variety of lesions. Adrenal lesions can either be primary, of adrenal origin, or secondary to other pathologies. Primary adrenal lesions can further be either of cortical or medullary origin. Functioning adrenal lesions can also give clues to the histologic diagnosis and direct workup. Over the years, various imaging techniques have been developed that have increased diagnostic accuracy and helped in better characterization of adrenal lesions non-invasively. In the first part of the two part series, we review adrenal imaging techniques and adrenal cortical tumors such as adenomas, adrenocortical tumors, adrenal hyperplasia and oncocytomas.

FDG-PET/CT characterization of adrenal nodules: diagnostic accuracy and interreader agreement using quantitative and qualitative methods

PURPOSE

To determine interreader agreement and diagnostic accuracy across varying levels of reader experience using qualitative and quantitative methods of evaluating adrenal nodules using ((18)F)-fluorodeoxyglucose-positron emission tomography/computed tomography.

METHODS

132 adrenal nodules (96 adenomas, 36 metastases) were retrospectively identified in 105 patients (49 men and 56 women, mean age 66 years, age range 45-85 years) with a history of lung cancer who underwent ((18)F)-fluorodeoxyglucose-positron emission tomography/computed tomography. For each nodule, three readers independently performed one qualitative and two quantitative measurements: visual assessment, standardized uptake value (SUVmax), and standard uptake ratio (SUVratio). Interreader agreement was calculated using percent agreement with κ statistic for qualitative analysis and intraclass correlation coefficient (ICC) for quantitative analysis. Accuracy, sensitivity, and specificity for distinguishing benign from malignant adrenal nodules were calculated for each method.

RESULTS

Percent agreement between readers for visual (qualitative) assessment was 92% to 96% and κ statistic was 0.79 to 0.90 (95% confidence limits 0.66-0.99). ICC for SUVmax was 92% to 99% (95% CL 0.8-1.0), and ICC for SUVratio was 89% to 99% (95% CL 0.74-0.99). For diagnosis of malignancy, mean sensitivity and specificity for visual assessment were 80% and 97%, respectively. Mean sensitivity and specificity for SUVmax were 91% and 81%, respectively; for SUVratio, 90% and 80%. Mean diagnostic accuracy was 93%, 83%, and 84% for visual assessment, SUVmax, and SUVratio, respectively.

CONCLUSION

Excellent interreader agreement is seen for quantitative and qualitative methods of distinguishing benign from malignant adrenal nodules. Qualitative analysis demonstrated higher accuracy but lower sensitivity compared with quantitative analysis.

Utilisation of combined 18F-FDG PET/CT scan for differential diagnosis between benign and malignant adrenal enlargement

OBJECTIVE

To assess the properties of adrenal lesions with and without known primary cancer and investigate predictors for differential diagnosis between benign and malignant adrenal enlargement.

METHODS

This retrospective study used fluorine-18 fludeoxyglucose positron emission tomography (PET)/CT in 325 patients with adrenal lesions (229 with known primary cancer and 96 without primary cancer). Age, sex, the presence of right and left masses, nodules or hyperplasia, unenhanced attenuation, maximum standardised uptake value (SUVmax) ratio, and the presence of metastasis in other body parts and locations of the primary cancer were assessed. Univariate and multivariate analyses were used to assess variables associated with risk of adrenal metastasis.

RESULTS

Patients with adrenal metastasis vs those without had a higher frequency of primary lung cancer (52.3% vs 30.7%) but a lower frequency of gastrointestinal cancer (7.9% vs 16.6%). The frequency of other abnormalities, including adenoma and hyperplasia, was similar between patients with and without known primary cancer. A higher proportion of patients with adrenal metastasis regardless of primary cancer site were younger, had a nodule or a mass, had an unenhanced attenuation of >10 HU, had an SUVmax ratio of >2.5, and had metastasis in other body parts. Analysis found independent associations of age, unenhanced attenuation of >10 HU, SUVmax ratio of >2.5 and the presence of metastasis in other body parts with adrenal metastasis. The combination of the four variables was strongly associated with adrenal metastasis.

CONCLUSION

PET/CT was useful in characterising adrenal lesions as benign or malignant and helpful in identifying adrenal metastasis and cancer severity.

ADVANCES IN KNOWLEDGE

PET/CT can help in the differential diagnosis between benign and malignant adrenal enlargement.

Functional characterization of adrenal lesions using [123I]IMTO-SPECT/CT

CONTEXT

Adrenal tumors are highly prevalent and represent a wide range of different pathological entities. Conventional imaging often provides only limited information on the origin of these lesions. Novel specific imaging methods are, therefore, of great clinical interest.

OBJECTIVE

We evaluated [(123)I]iodometomidate ([(123)I]IMTO) imaging for noninvasive characterization of adrenal masses.

DESIGN/SETTING

This was a prospective monocentric diagnostic study in a tertiary care center.

PATIENTS AND INTERVENTION

A total of 51 patients with an adrenal lesion underwent [(123)I]IMTO imaging after injection of 185 MBq of [(123)I]IMTO. Sequential planar whole-body scans until 24 hours postinjection and single photon emission computed tomography (SPECT)/computed tomography imaging 4 to 6 hours postinjection were performed.

MAIN OUTCOME MEASURE

Sensitivity and specificity of [(123)I]IMTO imaging for the noninvasive characterization of adrenal lesions were measured.

RESULTS

Adrenocortical tissue showed high and specific tracer uptake with a short investigation time and low radiation exposure. Qualitative analysis of SPECT/computed tomography data resulted in a sensitivity of 89% and a specificity of 85% for differentiating adrenocortical tumors from lesions of nonadrenocortical origin. Receiver-operating characteristic analysis of semiquantitative data revealed a sensitivity of 83% and a specificity of 86% for identification of adrenocortical lesions at a cutoff value of tumor to liver ratio of 1.3.

CONCLUSIONS

[(123)I]IMTO is a highly specific radiotracer for imaging of adrenocortical tissue with a short investigation time and low radiation exposure. Because of the general availability of SPECT technology, [(123)I]IMTO scintigraphy has the potential to become a widely used tool to noninvasively characterize the biology of adrenal lesions.

Molecular imaging of adrenal neoplasms

The adrenal glands are complex structures from which a variety of benign and malignant tumors may arise and are a common site of metastatic disease. Several radiopharmaceuticals are used for imaging the adrenals, including I-123/I-131 metaiodobenzylguanidine (MIBG), norcholesterol derivatives, In-111 pentetreotide and Ga-68 somatostatin analogs, [F-18]fluorodeoxyglucose, [F-18]fluorodopa, [F-18]fluorodopamine, C-11 meta hydroxyephedrine, and C-11/F-18/I-123 Metomidate (MTO) or its analogs. In this review we focus on the role of these reagents in metastatic lesions, cortical neoplasms, pheochromocytoma/paraganglioma, and neuroblastoma (NB).

Adrenal imaging: a primer for oncosurgeons

Differentiation of an incidental adrenal lesion into benign and malignant etiologies is an endeavor with significant and obvious clinical benefit. Advances in imaging now enable this differentiation in high proportion of patients in a non-invasive manner. The ACR guidelines elaborated in this review seek to promote clinically meaningful, evidence-based approach to an IAL. Knowledge of the potential as well the limitations of individual modalities is essential so as to streamline investigations in a cost-effective manner.

Targeting insulin inhibition as a metabolic therapy in advanced cancer: a pilot safety and feasibility dietary trial in 10 patients

OBJECTIVE

Most aggressive cancers demonstrate a positive positron emission tomographic (PET) result using ¹⁸F-2-fluoro-2-deoxyglucose (FDG), reflecting a glycolytic phenotype. Inhibiting insulin secretion provides a method, consistent with published mechanisms, for limiting cancer growth.

METHODS

Eligible patients with advanced incurable cancers had a positive PET result, an Eastern Cooperative Oncology Group performance status of 0 to 2, normal organ function without diabetes or recent weight loss, and a body mass index of at least 20 kg/m². Insulin inhibition, effected by a supervised carbohydrate dietary restriction (5% of total kilocalories), was monitored for macronutrient intake, body weight, serum electrolytes, β-hydroxybutyrate, insulin, and insulin-like growth factors-1 and -2. An FDG-PET scan was obtained at study entry and exit.

RESULTS

Ten subjects completed 26 to 28 d of the study diet without associated unsafe adverse effects. Mean caloric intake decreased 35 ± 6% versus baseline, and weight decreased by a median of 4% (range 0.0-6.1%). In nine patients with prior rapid disease progression, five with stable disease or partial remission on PET scan after the diet exhibited a three-fold higher dietary ketosis than those with continued progressive disease (n = 4, P = 0.018). Caloric intake (P = 0.65) and weight loss (P = 0.45) did not differ in those with stable disease or partial remission versus progressive disease. Ketosis was associated inversely with serum insulin levels (P = 0.03).

CONCLUSION

Preliminary data demonstrate that an insulin-inhibiting diet is safe and feasible in selected patients with advanced cancer. The extent of ketosis, but not calorie deficit or weight loss, correlated with stable disease or partial remission. Further study is needed to assess insulin inhibition as complementary to standard cytotoxic and endocrine therapies.

Imaging of adrenal masses with emphasis on adrenocortical tumors

Because of the more widespread and frequent use of cross-sectional techniques, mainly computed tomography (CT), an increasing number of adrenal tumors are detected as incidental findings (“incidentalomas”). These incidentaloma patients are much more frequent than those undergoing imaging because of symptoms related to adrenal disease. CT and magnetic resonance imaging (MRI) are in most patients sufficient for characterization and follow-up of the incidentaloma. In a minor portion of patients, biochemical screening reveals a functional tumor and further diagnostic work-up and therapy need to be performed according to the type of hormonal overproduction. In oncological patients, especially when the morphological imaging criteria indicate an adrenal metastasis, biopsy of the lesion should be considered after pheochromocytoma is ruled out biochemically. In the minority of patients in whom CT and MRI fail to characterize the tumor and when time is of essence, functional imaging mainly by positron emission tomography (PET) is available using various tracers. The most used PET tracer, [¹⁸F]fluoro-deoxy-glucose (¹⁸FDG), is able to differentiate benign from malignant adrenal tumors in many patients. ¹¹C-metomidate (¹¹C-MTO) is a more specialized PET tracer that binds to the 11-beta-hydroxylase enzyme in the adrenal cortex and thus makes it possible to differ adrenal tumors (benign adrenocortical adenoma and adrenocortical cancer) from those of non-adrenocortical origin.

Metomidate-based imaging of adrenal masses

Due to broader use of conventional imaging techniques, adrenal tumors are detected with increasing frequency comprising a wide variety of different tumor entities. Despite improved conventional imaging techniques, a significant number of adrenal lesions remain that cannot be easily determined. A particular diagnostic challenge are lesions in patients with known extra-adrenal malignancy because these patients frequently harbor adrenal metastases. Furthermore, adrenal masses with low fat content and no detectable hormone excess are difficult to diagnose properly. Fine needle biopsy is invasive, often unsuccessful, and puts patients at risk, e. g., in cases of pheochromocytoma or adrenal cancer. Noninvasive characterization using radiotracers has therefore been established in recent years. (18)F-FDG PET helps to differentiate benign from malignant lesions. However, it does not distinguish between adrenocortical or nonadrenocortical lesions (e.g., metastases or adrenocortical carcinoma). More recently, enzyme inhibitors have been developed as tracers for adrenal imaging. Metomidate is most widely used. It binds with high specificity and affinity to CYP11B enzymes of the adrenal cortex. As these enzymes are exclusively expressed in adrenocortical cells, uptake of labeled metomidate tracers has been shown to be highly specific for adrenocortical neoplasia. (11)C-metomidate PET and (123)I-iodometomidate SPECT imaging has been introduced into clinical use. Both tracers not only distinguish between adrenocortical and nonadrenocortical lesions but are also able to visualize metastases of adrenocortical carcinoma. The very specific uptake has recently led to first application of (131)I-iodometomidate for radiotherapy in ACC. In conclusion, metomidate-based imaging is an important complementary tool to diagnose adrenal lesions that cannot be determined by other methods.

PET/CT in the staging of the non-small-cell lung cancer

Lung cancer is a common disease and the leading cause of cancer-related death in many countries. Precise staging of patients with non-small-cell lung cancer plays an important role in determining treatment strategy and prognosis. Positron emission tomography/computed tomography (PET/CT), combining anatomic information of CT and metabolic information of PET, is emerging as a potential diagnosis and staging test in patients with non-small-cell lung cancer (NSCLC). The purpose of this paper is to discuss the value of integrated PET/CT in the staging of the non-small-cell lung cancer and its health economics.

Adrenal incidentalomas

The term adrenal incidentaloma (AI) is usually defined as an adrenal mass unexpectedly detected through an imaging procedure performed for reasons a priori unrelated to adrenal dysfunction or suspected dysfunction. The preferred approach to their management in terms of diagnosis, follow-up, and treatment remain controversial despite a state-of-the-science conference sponsored by the U.S. National Institutes of Health. Although most experts' recommendations tend to be relatively minor variations of the conference's approach, dissenting voices have been heard. Despite their frequent appearance, the challenge remains to recognize and treat the small percentage of AI that do pose a significant risk, either because of their hormonal activity or because of their malignant histology, while leaving the rest alone. Although the differential diagnosis of an incidentally discovered mass is quite extensive, most AIs are non-secreting cortical adenomas. The noninvasive differentiation of benign and malignant lesions depends upon imaging characteristics, and sometimes radiologic diagnosis can be definitive, but often it is not, Among function lesions, autonomous cortisol production seems to be the most common and may be associated with increased cardiovascular risk and clinical features of the "metabolic syndrome." Follow-up of cases in which a specific diagnosis is not made initially involves assessment for growth and development of hormonal function, but even here, controversy about the extent of evaluation persists.

Adrenal imaging

Adrenal masses are frequently encountered in imaging practices. Simple detection by radiologists is insufficient as many of these masses can now be characterized by imaging alone. Some masses can be characterized by their simple appearances, but most cannot. This article will describe the different principles used by imagers to lead them to the correct diagnosis for the overwhelming majority of lesions. Imagers should be familiar with these techniques to expedite treatment, especially in cancer patients and so prevent unnecessary biopsies, costs, and anxiety.

Predictive factors for malignant pheochromocytoma: analysis of 136 patients

PURPOSE

We evaluated the clinical characteristic, tumor feature and immunohistochemistry factors predicting malignant pheochromocytoma.

MATERIALS AND METHODS

Between January 1999 and December 2008 we retrospectively reviewed the records of 136 patients with pheochromocytoma at Ruijin Hospital. We compared clinical characteristics (age, gender, symptoms and biochemical analysis), tumor features (site, weight and diameter) and the expression of 3 angiogenesis/metastasis related genes (VEGF, Cox-2 and MVD) by immunohistochemical analysis of benign vs malignant pheochromocytomas.

RESULTS

Of the 136 patients 105 (77%) had benign and 31 (23%) had malignant pheochromocytoma. Malignant tumors were larger and heavier than benign tumors, and accompanied by higher plasma metanephrine secretion (each p <0.001). Mean tumor catecholamine and preoperative 24-hour urinary metanephrine or normetanephrine were obviously higher in malignant than in benign tumors (p <0.001). Also, 25 malignant tumors (81%) were immunopositive for VEGF while only 24 benign tumors (23%) showed this characteristic (p <0.001). Microvessel density and the rate of positive staining for Cox-2 protein in malignant samples were higher than in benign samples (p <0.001).

CONCLUSIONS

Several promising predictive parameters are currently available to distinguish benign from malignant pheochromocytoma. Large (5 cm or greater) or heavy (250 gm or greater) tumors, multifocal and extra-adrenal tumors, early onset postoperative hypertension and higher plasma or urine metadrenaline are high risk factors predictive of malignant pheochromocytoma. Also, expression of the 3 angiogenesis or metastasis related genes VEGF, Cox-2 and MVD helps determine the diagnosis of malignancy and suggests strict followup.

Characterization of adrenal masses by using FDG PET: a systematic review and meta-analysis of diagnostic test performance

PURPOSE

To perform a systematic review and meta-analysis of published data to determine the diagnostic utility of adrenal fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) for distinguishing benign from malignant adrenal disease.

MATERIALS AND METHODS

Data on FDG PET assessment in MEDLINE and other electronic databases (from inception to November 2009) and in subject matter-specific journals were evaluated and compared with histologic diagnoses and/or established clinical and imaging follow-up results. Methodologic quality was assessed by using Quality Assessment of Diagnostic Accuracy Studies criteria. Bivariate random-effects meta-analytical methods were used to estimate summary and subgroup-specific sensitivity, specificity, and receiver operating characteristic curves and to investigate the effects of study design characteristics and imaging procedure elements on diagnostic accuracy.

RESULTS

A total of 1391 lesions (824 benign, 567 malignant) in 1217 patients from 21 eligible studies were evaluated. Qualitative (visual) analysis of 841 lesions (in 14 reports) and quantitative analyses based on standardized uptake values (SUVs) for 824 lesions (in 13 reports) and standardized uptake ratios (SURs) for 562 lesions (in eight reports) were performed. Resultant data were highly heterogeneous, with a model-based inconsistency index of 88% (95% confidence interval [CI]: 79%, 98%). Mean sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio values for differentiating between benign and malignant adrenal disease were 0.97 (95% CI: 0.93, 0.98), 0.91 (95% CI: 0.87, 0.94), 11.1 (95% CI: 7.5, 16.3), 0.04 (95% CI: 0.02, 0.08), and 294 (95% CI: 107, 805), respectively, with no significant differences in accuracy among the visual, SUV, and SUR analyses.

CONCLUSION

Meta-analysis of combination PET-computed tomography (CT) reports revealed that FDG PET was highly sensitive and specific for differentiating malignant from benign adrenal disease. Diagnostic accuracy was not influenced by the type of imaging device (PET vs PET/CT), but specificity was dependent on the clinical status (cancer vs no cancer).

Evaluation of incidentally discovered adrenal masses with PET and PET/CT

BACKGROUND AND PURPOSE

Incidentally discovered adrenal masses are commonly seen with high resolution diagnostic imaging performed for indications other than adrenal disease. Although the majority of these masses are benign and non-secretory, their unexpected discovery prompts further biochemical and often repeated imaging evaluations, sufficient to identify hormonally active adrenal masses and/or primary or metastatic neoplasms to the adrenal(s). In the present paper we investigate the role of PET and PET/CT for the detection of adrenal incidentalomas in comparison with CT and MRI.

MATERIALS AND METHODS

a systematic revision of the papers published in PubMed/Medline until September 2010 was done.

RESULTS

The diagnostic imaging approach to incidentally discovered adrenal masses includes computed tomography (CT), magnetic resonance imaging (MRI) and more recently positron emission tomography (PET) with radiopharmaceuticals designed to exploit mechanisms of cellular metabolism, adrenal substrate precursor uptake, or receptor binding.

CONCLUSION

The functional maps created by PET imaging agents and the anatomic information provided by near-simultaneously acquired, co-registered CT facilitates localization and diagnosis of adrenal dysfunction, distinguishes unilateral from bilateral disease, and aids in characterizing malignant primary and metastatic adrenal disease.

An unusual case of adrenal metastasis from colorectal cancer: computed tomography and fluorine 18-fluoro-deoxy-glucose positron emission tomography-computed tomography features and literature review

Incidentally discovered adrenal masses are a common diagnostic problem. While computed tomography (CT) and magnetic resonance (MR) imaging can adequately characterize most benign or malignant adrenal masses, in some cases the results are indeterminate. We report and discuss a case of an adrenal metastasis with misleading clinical and CT features, in which an abnormal metabolic uptake detected through fluorine 18-fluoro-deoxy-glucose positron emission tomography (¹⁸F-FDG PET)-CT raised the suspicion of adrenal metastasis relatively early compared with apparently normal results on repeated follow-up CT examinations.

Physiology and pathophysiology of incidental findings detected on FDG-PET scintigraphy

A routine feature of positron emission tomography/computed tomography (PET/CT) imaging is whole-body acquisition that results in many unexpected findings identified outside of the primary region of abnormality. Furthermore, (18)F-fluorodeoxyglucose (FDG) is a marker of glycolysis and does not specifically accumulate in malignancy. Understanding the physiology and pathophysiology of normal FDG distribution and common incidental findings is therefore essential to the physician interpreting whole-body FDG-PET/CT studies. Whereas many incidental findings are benign and of limited clinical significance, others represent uncommon manifestations of the primary malignancy, second malignancies, or various clinically significant pathologic processes. Patients with a single malignancy are at greater risk of developing synchronous or metachronous second malignancies, possibly related to exposure to shared carcinogenic agents or presence of prooncogenic mutations. The decision of how to pursue an intervention on the basis of an incidental finding is generally left to clinical judgment.

Imaging and 'omic' methods for the molecular diagnosis of cancer

Molecular imaging methods can noninvasively detect specific biological processes that are aberrant in cancer, including upregulated glycolytic metabolism, increased cellular proliferation and altered receptor expression. PET using the glucose analogue 18F-fluoro-2-deoxyglucose, which detects the increased glucose uptake that is a characteristic of tumor cells, has been widely used in the clinic to detect tumors and their responses to treatment; however, there are many new PET tracers being developed for a wide range of biological targets. Magnetic resonance spectroscopy (MRS), which can be used to detect cellular metabolites, can also provide prognostic information, particularly in brain, breast and prostate cancers. An emerging technique, which by hyperpolarizing 13C-labeled cell substrates dramatically enhances their sensitivity to detection, could further extend the use of MRS in molecular imaging in the clinic. Molecular diagnostics applied to serum samples or tumor samples obtained by biopsy, can measure changes at the individual cell level and the underlying changes in gene or protein expression. DNA microarrays enable high-throughput gene-expression profiling, while mass spectrometry can detect thousands of proteins that may be used in the future as biomarkers of cancer. Probing molecular changes will aid not only cancer diagnosis, but also provide tumor grading, based on gene-expression analysis and imaging measurements of cell proliferation and changes in metabolism; staging, based on imaging of metastatic spread and elevation of protein biomarkers; and the detection of therapeutic response, using serial molecular imaging measurements or monitoring of serum markers. The present article provides a summary of the molecular diagnostic methods that are currently being trialed in the clinic.

Incidental non-secreting adrenal masses in cancer patients: intra-individual comparison of 18F-fluorodeoxyglucose positron emission tomography/computed tomography with computed tomography and shift magnetic resonance imaging

The ability of integrated (18)F-fluorodeoxyglucose positron emission tomography and computed tomography (FDG PET/CT) to distinguish between benign and malignant incidental non-secreting adrenal masses was evaluated in cancer patients. Results were compared with those of CT and shift magnetic resonance imaging (MRI). A total of 1832 cancer patients who had undergone FDG PET/CT scans were retrospectively evaluated. Visual interpretation, tumour maximum standardized uptake value (SUV(max)), liver SUV(max) and tumour/liver SUV(max) ratios were correlated with the findings of CT, shift MRI and final diagnosis (based on biopsy or clinical/radiological follow-up). A total of 109 adrenal masses were found: 49 were malignant and 60 were benign on final diagnosis. A tumour/liver SUV(max) ratio threshold of 1.0 was more accurate in differentiating the tumour type than tumour SUV(max) or visual interpretation alone. Diagnostic accuracy of CT and shift MRI (92 - 97%) was similar to that for FDG PET/CT (94 - 97%). In conclusion, FDG PET/CT accurately characterizes adrenal tumours, with excellent sensitivity and specificity. Use of 1.0 as the threshold for the tumour/liver SUV(max) ratio seems to be promising for distinguishing benign from malignant adrenal masses in cancer patients.

Adrenal imaging

OBJECTIVE

Adrenal nodules are frequently encountered on current high-resolution imaging, and accurate characterization of such lesions is critical for appropriate patient care. Our article highlights how imaging techniques such as CT densitometry, CT washout characteristics, chemical shift MRI, PET, and PET/CT help characterize most adrenal lesions. We focus on these techniques as well as specifically, because of space constraints, the varied imaging appearances of adrenocortical carcinoma, pheochromocytoma, and lymphoma on these techniques.

CONCLUSION

The imaging characterization of adrenal lesions has continued to advance over the past decade as new technologies have evolved. CT, MRI, PET, and PET/CT are now established clinical techniques capable of differentiating benign from malignant adrenal lesions.