Value of 18-F-FDG PET/CT and CT in the Diagnosis of Indeterminate Adrenal Masses

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.

The Diagnostic Value of 18F-FDG PET/CT Scan in Characterizing Adrenal Tumors

CONTEXT

Imaging plays an important role in the characterization of adrenal tumors, but findings might be inconclusive. The clinical question is whether 18F fluodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) is of diagnostic value in this setting.

OBJECTIVE

This meta-analysis was aimed at the diagnostic value of 18F-FDG PET/CT in differentiating benign from malignant adrenal tumors discovered either as adrenal incidentaloma or during staging or follow-up of oncologic patients.

DATA SOURCES

PubMed, EMBASE, Web of Science, and Cochrane Library were searched to select articles between 2000 and 2021.

STUDY SELECTION

We included studies describing the diagnostic value of 18F-FDG PET/CT in adult patients with an adrenal tumor. Exclusion criteria were 10 or fewer participants, insufficient data on histopathology, clinical follow-up, or PET results. After screening of title and abstract by 2 independent reviewers, 79 studies were retrieved, of which 17 studies met the selection criteria.

DATA EXTRACTION

Data extraction using a protocol and quality assessment according to QUADAS-2 was performed independently by at least 2 authors.

DATA SYNTHESIS

A bivariate random-effects model was applied using R (version 3.6.2.). Pooled sensitivity and specificity of 18F-FDG PET/CT for identifying malignant adrenal tumors was 87.3% (95% CI, 82.5%-90.9%) and 84.7% (95% CI, 79.3%-88.9%), respectively. The pooled diagnostic odds ratio was 9.20 (95% CI, 5.27-16.08; P < .01). Major sources of heterogeneity (I2, 57.1% [95% CI, 27.5%-74.6%]) were in population characteristics, reference standard, and interpretation criteria of imaging results.

CONCLUSIONS

18F-FDG PET/CT had good diagnostic accuracy for characterization of adrenal tumors. The literature, however, is limited, in particular regarding adrenal incidentalomas. Large prospective studies in well-defined patient populations with application of validated cutoff values are needed.

Clinical, pathophysiologic, genetic and therapeutic progress in Primary Bilateral Macronodular Adrenal Hyperplasia

Patients with primary bilateral macronodular adrenal hyperplasia (PBMAH) usually present bilateral benign adrenocortical macronodules at imaging and variable levels of cortisol excess. PBMAH is a rare cause of primary overt Cushing's syndrome, but may represent up to one third of bilateral adrenal incidentalomas with evidence of cortisol excess. The increased steroidogenesis in PBMAH is often regulated by various G-protein coupled receptors aberrantly expressed in PBMAH tissues; some receptor ligands are ectopically produced in PBMAH tissues creating aberrant autocrine/paracrine regulation of steroidogenesis. The bilateral nature of PBMAH and familial aggregation, led to the identification of germline heterozygous inactivating mutations of the ARMC5 gene, in 20-25% of the apparent sporadic cases and more frequently in familial cases; ARMC5 mutations/pathogenic variants can be associated with meningiomas. More recently, combined germline mutations/pathogenic variants and somatic events inactivating the KDM1A gene were specifically identified in patients affected by GIP-dependent PBMAH. Functional studies demonstrated that inactivation of KDM1A leads to GIP-receptor (GIPR) overexpression and over or down-regulation of other GPCRs. Genetic analysis is now available for early detection of family members of index cases with PBMAH carrying identified germline pathogenic variants. Detailed biochemical, imaging, and co-morbidities assessment of the nature and severity of PBMAH is essential for its management. Treatment is reserved for patients with overt or mild cortisol/aldosterone or other steroid excesses taking in account co-morbidities. It previously relied on bilateral adrenalectomy; however recent studies tend to favor unilateral adrenalectomy, or less frequently, medical treatment with cortisol synthesis inhibitors or specific blockers of aberrant GPCR.

The F-18 FDG PET/CT evaluation of the metastatic adrenal lesions of the non-lung cancer tumors compared with pathology results

Background

The aim of this study was to evaluate the role of F-18 FDG PET/CT imaging in the diagnosis of primary and metastatic adrenal tumors that originate from non-lung cancer primary tumors.

Results

F-18 FDG PET/CT images of patients (8 male and 6 female; mean: 55.36 ± 16.2 years old) who attended with the diagnosis of primary or adrenal metastatic lesions other than lung cancer metastasis were evaluated in a retrospective manner. The diameter of the adrenal lesions was mean: 23.93 ± 36.6 mm with SUVmax levels of mean: 9.98 ± 7.8. The primary site of 2/3 of the patients with unknown primary was the adrenal gland, and in one of the patients primary tumor remained unknown during follow-up.

Conclusions

According to the results of this study, F-18 FDG PET/CT has high diagnostic performance in the diagnosis of the adrenal gland primary and metastatic lesions, which originate from non-lung cancer tumors. Further studies in the larger series are warranted.

Efficacy of PET-CT in the prediction of metastatic adrenal masses that are detected on follow-up of the patients with prior nonadrenal malignancy: A nationwide multicenter case-control study

Metastasis is the second most common type of adrenal gland mass. In patients undergoing follow-up for nonadrenal malignancy, adrenalectomy is performed when metastasis to adrenal gland is suspected on the basis of positron emission tomography-computed tomography (PET-CT) imaging. This study investigated the efficacy of PET-CT in the discrimination of metastatic lesions from nonmetastatic lesions in the adrenal glands. In this multicentric study, data was collected from enrolled centers. Forty-one patients who underwent surgery for suspected adrenal metastases were evaluated retrospectively. The following data types were collected: demographic, primary tumor, maximum standardized uptake value of adrenal mass (a-SUVx) and detectability in computed tomography and/or magnetic resonance imaging, and specimen size and histopathology. Six patients were excluded due to unavailability of PET-CT reports and 4 for being primary adrenal malignancy. The rest were divided into 2 groups (metastatic: n = 17, 55% and nonmetastatic: n = 14, 45%) according to histopathology reports. There was no statistical difference between the analyzed values, except the a-SUVx (P < .05). The a-SUVx cutoff value was defined as 5.50 by receiver operating characteristic curves and compared with literature. There was no statistical difference when each group was divided as low and high (P > .05). It was found that PET-CT was able to discriminate metastatic lesions from primary benign lesions (P = .022). PET-CT can discriminate primary benign lesions and metastatic lesions by cutoff 5.5 value for a-SUVx.

Primary adrenal tuberculosis infection in patients with Behcet's disease presenting as isolated adrenal metastasis by 18F-FDG PET/CT: a rare case report and literature review

Primary adrenal tuberculosis (TB) is a rare type of extrapulmonary tuberculosis (EPTB). A pathological biopsy is usually required to make a definite diagnosis due to nonspecific symptoms. Antituberculous chemotherapy is the main treatment regimen, and cortisol replacement therapy should be added when adrenal insufficiency is involved. Here, we present a 59-year-old man who had recurrence of oral and genital aphthosis for 3 years and was diagnosed with Behcet's disease (BD), which was cured by thalidomide. After 10 days of admission, the patient had sudden abdominal pain in the right upper quadrant with high fever and was diagnosed with acute cholecystitis attack, which was treated by percutaneous transhepatic gallbladder drainage (PTGBD). Further contrast-enhanced CT showed a right adrenal mass with a diameter of 2.0 cm, and PET-CT indicated intense ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) uptake in the right adrenal mass with a maximum standardized uptake value (SUV_max) of 15.2. As a metastatic adrenal mass was suspected, the patient underwent retroperitoneal laparoscopic adrenalectomy. Histopathological and immunohistochemical analysis revealed primary adrenal TB. After routine anti-tuberculosis treatment with isoniazid, rifampin, pyrazinamide and ethambutol for six months, the patient was cured and discharged. In summary, primary unilateral adrenal TB without adrenal insufficiency is difficult to diagnose only on the basis of clinical manifestations and examinations. Further studies are needed to develop an easier and more accurate diagnostic examination.

18F-FDG-PET/CT Evaluation of Indeterminate Adrenal Masses in Noncancer Patients

CONTEXT

Adrenal tumors in noncancer patients are common.

OBJECTIVE

Evaluate performance of 18F-fluorodeoxyglucose positron emission tomography computed tomography (18F-FDG-PET/CT) in distinguishing between benign and malignant adrenal tumors.

DESIGN

Retrospective chart review 2010-2019.

SETTING

Academic institution.

PATIENTS

One hundred and seventeen noncancer patients, defined as having no history of cancer or with cancer in remission for ≥5 years, completed 18F-FDG-PET/CT to evaluate adrenal masses, with pathologic diagnoses or imaging follow-up (≥12 months).

INTERVENTION

18F-FDG-PET/CT of 117 indeterminate adrenal masses.

MAIN OUTCOME MEASURES

Receiver operator characteristic curve of the ratios of adrenal lesion standardized uptake value (SUV)max to liver SUVmean and of adrenal lesion SUVmax to aortic arch blood pool SUVmean were constructed.

RESULTS

Seventy benign and 47 malignant masses (35 adrenocortical carcinomas [ACCs], 12 adrenal metastases) were identified. Malignant masses had higher median liver SUV and blood pool SUV ratios than benign masses (6.2 and 7.4 vs 1.4 and 2.0, P < .001). Median liver and blood pool SUV ratios of ACC (6.1 and 7.3, respectively) and metastases (6.7 and 7.7, respectively) were higher than those of than adenomas (1.4 and 2.2, P < .05 for all comparisons). Optimal liver SUV ratio to discern between benign and malignant masses was 2.5, yielding 85% sensitivity, 90% specificity, and 7 false negative results (including 3 ACCs). Optimal blood pool SUV ratio was 3.4, yielding 83% sensitivity, 90% specificity, and 8 false negative results (including 4 ACCs).

CONCLUSION

When used in conjunction with other clinical assessments, 18F-FDG-PET/CT can be a valuable tool in evaluating adrenal masses in noncancer patients.

Risk stratification of adrenal masses by [18 F]FDG PET/CT: Changing tactics

CONTEXT

[¹⁸ F]FDG PET/CT improves adrenal tumour characterization. However, there is still no consensus regarding the optimal imaging biomarkers of malignancy.

OBJECTIVES

To assess the performance of Tumour standardized uptake value (SUV)_max :Liver SUV_max for malignancy-risk and to build and evaluate a prediction model.

DESIGN/METHODS

The cohort consisted of consecutive patients with adrenal masses evaluated by [¹⁸ F]FDG PET/CT. The gold standard for malignancy was based on histology or a multidisciplinary consensus in nonoperated cases. The performance of the previously reported cut-off for Tumour SUV_max :Liver SUV_max (>1.5) was evaluated in this independent cohort. Additionally, a predictive model of malignancy was built from the training cohort (previous study) and evaluated in the validation cohort (current study).

RESULTS

Sixty-four patients were evaluated; 28% of them had a Cushing's syndrome. Fifty-four adrenal masses were classified as benign and 10 as malignant (including 7 adrenocortical carcinomas). Compared to benign masses, malignant lesions were larger in size, had higher unenhanced densities and higher [¹⁸ F]FDG uptake. CT-derived anthropometric parameters did not differ between benign and malignant masses. A tumour SUV_max :Liver SUV_max  > 1.5 showed a good diagnostic performance: Se = 90.0%/Sp = 92.6%/PPV = 69.2%/NPV = 98.0% and accuracy = 92.2%. A predictive model based on tumour size and tumour-to-liver uptake SUV_max ratio for malignancy-risk was validated and provides a complementary approach to the ratio.

CONCLUSIONS

Tumour SUV_max :Liver SUV_max uptake ratio is a useful biomarker for diagnosis of adrenal masses. Another tactic would be to calculate with the model an individual risk of malignancy and integrate this information into a shared decision-making process.

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.

Diagnostic value of positron-emission tomography textural indices for malignancy of 18F-fluorodeoxyglucose-avid adrenal lesions

BACKGROUND

PET Textural indices could have an add-on diagnostic value for diagnosis of malignancy in patients with FDG-avid adrenal lesions.

METHODS

Consecutive patients referred for a FDG-PET/CT to our nuclear medicine department from June 2012 to June 2017 were retrospectively screened. Inclusion criteria were: patients with a FDG-avid adrenal lesion (uptake≥liver background); malignant/benign lesion confirmed histologically or with follow-up imaging examination. Pheochromocytomas were not included in the analysis. For each adrenal lesion, 5 quantitative PET parameters (SUV<inf>max</inf>, MTV, TLG, TLR<inf>max</inf> and TLRmean<inf>)</inf> were calculated. Thirty-seven textural indices were extracted using LIFEx software^®. Diagnostic performance to determine malignancy was assessed with a ROC analysis. Parameters with a significantly AUC>0.5 were selected and groups of highly correlated (r>0.8) parameters were created. A scoring system combining PET and textural indices was examined.

RESULTS

PET textural indices were calculated for 53 lesions (37 malignant, 16 benign). Three PET metabolic parameters (SUV<inf>max</inf>, TLR<inf>max</inf>, TLRmean) and 13 textural indices had an AUC>0.5. Seven groups of highly correlated parameters (r>0.8) were extracted. For PET parameters, SUV<inf>max</inf> had the best AUC (0.89 95% CI [0.79-0.98]; cut-off=7.0). For textural indices, ZLNU had the best AUC (0.87 95% CI [0.78-0.96]; cut-off=34.7) and specificity of 100%. Three scores combining the best four textural indices alone (Contrast<inf>GLCM</inf>, LRHGE, SZE and ZLNU) or with one PET parameters (SUV<inf>max</inf>, TLR<inf>max</inf>) were developed but did not increase the diagnostic performance (AUC≤0.89). ZLNU was the best parameter to distinguish primary adrenal cancer from adrenal metastases in malignant lesions (P<0.001).

CONCLUSIONS

Our study highlighted excellent diagnostic performance of several PET textural indices comparable to that of PET metabolic parameters. However, our results did not find any additional diagnostic value of textural indices when combined with metabolic parameters.

Severe Congenital Adrenal Hyperplasia Presenting as Bilateral Testicular Tumors and Azoospermia in the Third Decade of Life

Classic forms of 21-hydroxylase deficiency (21OHD) are usually diagnosed at birth by salt wasting or precocious puberty in male patients. Here we report the case of a 32-year-old male patient who presented with azoospermia and bilateral testicular tumors. He was referred to our endocrine unit after testicular surgery. His gonadotropins were undetectable. Liquid chromatography-tandem mass spectrometry revealed a high serum progesterone level, high 17-hydroxyprogesterone (17OHP) (255 ng/mL), and high levels of 17OHP metabolites, suggesting a classic form of 21OHD. His blood pressure was normal. Molecular analysis showed a homozygous large 21-hydroxylase gene (CYP21A2) conversion. Furthermore, an adrenal CT scan revealed voluminous, heterogeneous bilateral and asymmetric adrenal masses containing calcifications. Our case report illustrates the fact that a classic form of 21OHD can be diagnosed in late adulthood, manifested by azoospermia and large adrenal tumors, associated with elevated 17OHP.

Diagnostic accuracy of 18F-FDG PET or PET/CT for the characterization of adrenal masses: a systematic review and meta-analysis

OBJECTIVE

We aimed to explore the role of the diagnostic accuracy of ¹⁸F fluodeoxyglucose PET (¹⁸F-FDG PET) or PET/CT for characterization of adrenal lesions through a systematic review and meta-analysis.

METHODS

The MEDLINE, EMBASE, and Cochrane Library database, from the earliest available date of indexing through 30 April 2017, were searched for studies evaluating the diagnostic performance of ¹⁸F-FDG PET or PET/CT for characterization of adrenal lesions. We determined the sensitivities and specificities across studies, calculated positive and negative likelihood ratios (LR + and LR-), and constructed summary receiver operating characteristic curves.

RESULTS

Across 29 studies (2421 patients), the pooled sensitivity for ¹⁸F-FDG PET or PET/CT was 0.91 [95% CI (0.88-0.94)] with heterogeneity (χ² = 141.8, p = 0.00) and a pooled specificity of 0.91 [95% CI (0.87-0.93)] with heterogeneity (χ² = 113.7, p = 0.00). Likelihood ratio (LR) syntheses gave an overall positive likelihood ratio (LR+) of 9.9 [95% CI (7.1-13.7)] and negative likelihood ratio (LR-) of 0.09 [95% CI (0.07-0.13)]. The pooled diagnostic odds ratio was 105 [95% CI (63-176)]. In metaregression analysis, study design, publication year, study location (western vs others), interpretation criteria of PET or PET/CT images, quantification of PET or PET/CT [SUV_max (maximum standardized uptake value) vs SUV (standardized uptake value) ratio], patient group, and analysis method (patient-based vs lesion-based) were the sources of the study heterogeneity. However, in multivariate metaregression, no definite variable was the source of the study heterogeneity.

CONCLUSION

¹⁸F-FDG PET or PET/CT demonstrated good sensitivity and specificity for the characterization of adrenal masses. At present, the literature regarding the use of ¹⁸F-FDG PET or PET/CT for the characterization of adrenal masses remains still limited; thus, further large multicenter studies would be necessary to substantiate the diagnostic accuracy of ¹⁸F-FDG PET or PET/CT characterization of adrenal masses. Advances in knowledge: ¹⁸F- FDG PET or PET/CT showed good sensitivity and specificity for the characterization of adrenal masses and could provide additional information for that purpose.

Radiology of the adrenal incidentalomas. Review of the literature

The term "adrenal incidentaloma" is a radiological term. Adrenal incidentalomas are adrenal tumors discovered in an imaging study that has been obtained for indications exclusive to adrenal conditions (Udelsman 2001; Linos 2003; Bulow et al. 2006; Anagnostis et al. 2009). This definition excludes patients undergoing imaging testing as part of staging and work-up for cancer (Grumbach et al. 2003; Anagnostis et al. 2009). Papierska et al. (2013) have added the prerequisite that the size of a tumor must be "greater than 1cm in diameter", in order to be called incidentaloma. Although in the most cases these masses are non-hypersecreting and benign, they still represent an important clinical concern because of the risk of malignancy or hormone hyperfunction (Barzon et al. 2003). Th e adrenal tumors belong to the commonest incidental findings having been discovered (Kanagarajah et al. 2012).

Increased F-FDG Uptake in Bilateral Gynecomastia Secondary to Feminizing Adrenal Tumor: A Rare Case Report and Review of Literature

A 21 year old male who presented with painful enlargement of both the breasts and a hyperestrogenic state, was found to harbor a heterogeneous mass arising from the right adrenal on contrast enhanced Computed Tomography abdomen. The mass was hypermetabolic with no regional, nodal or distant metastases on Fluorine-18 Fluorodeoxyglucose Positron Emission Tomography /Computed Tomography examination. Notably, substantial tracer uptake was seen in bilateral gynecomastia. The patient underwent a right adrenalectomy with the histopathology report confirming adrenocortical carcinoma. This case demonstrates utility of FDG PET/CT in adrenocortical carcinoma. However, when interpreting FDG PET/CT as a staging tool in oncological male patients, one should consider gynecomastia as a possible cause for increased FDG uptake in the breast as it may lead to a false positive interpretation.

Management of adrenal incidentalomas: European Society of Endocrinology Clinical Practice Guideline in collaboration with the European Network for the Study of Adrenal Tumors

: By definition, an adrenal incidentaloma is an asymptomatic adrenal mass detected on imaging not performed for suspected adrenal disease. In most cases, adrenal incidentalomas are nonfunctioning adrenocortical adenomas, but may also represent conditions requiring therapeutic intervention (e.g. adrenocortical carcinoma, pheochromocytoma, hormone-producing adenoma or metastasis). The purpose of this guideline is to provide clinicians with best possible evidence-based recommendations for clinical management of patients with adrenal incidentalomas based on the GRADE (Grading of Recommendations Assessment, Development and Evaluation) system. We predefined four main clinical questions crucial for the management of adrenal incidentaloma patients, addressing these four with systematic literature searches: (A) How to assess risk of malignancy?; (B) How to define and manage low-level autonomous cortisol secretion, formerly called 'subclinical' Cushing's syndrome?; (C) Who should have surgical treatment and how should it be performed?; (D) What follow-up is indicated if the adrenal incidentaloma is not surgically removed? SELECTED RECOMMENDATIONS: (i) At the time of initial detection of an adrenal mass establishing whether the mass is benign or malignant is an important aim to avoid cumbersome and expensive follow-up imaging in those with benign disease. (ii) To exclude cortisol excess, a 1mg overnight dexamethasone suppression test should be performed (applying a cut-off value of serum cortisol ≤50nmol/L (1.8µg/dL)). (iii) For patients without clinical signs of overt Cushing's syndrome but serum cortisol levels post 1mg dexamethasone >138nmol/L (>5µg/dL), we propose the term 'autonomous cortisol secretion'. (iv) All patients with '(possible) autonomous cortisol' secretion should be screened for hypertension and type 2 diabetes mellitus, to ensure these are appropriately treated. (v) Surgical treatment should be considered in an individualized approach in patients with 'autonomous cortisol secretion' who also have comorbidities that are potentially related to cortisol excess. (vi) In principle, the appropriateness of surgical intervention should be guided by the likelihood of malignancy, the presence and degree of hormone excess, age, general health and patient preference. (vii) Surgery is not usually indicated in patients with an asymptomatic, nonfunctioning unilateral adrenal mass and obvious benign features on imaging studies. We provide guidance on which surgical approach should be considered for adrenal masses with radiological findings suspicious of malignancy. Furthermore, we offer recommendations for the follow-up of patients with adrenal incidentaloma who do not undergo adrenal surgery, for those with bilateral incidentalomas, for patients with extra-adrenal malignancy and adrenal masses and for young and elderly patients with adrenal incidentalomas.

MANAGEMENT OF ENDOCRINE DISEASE: Imaging for the diagnosis of malignancy in incidentally discovered adrenal masses: a systematic review and meta-analysis

OBJECTIVE

Adrenal masses are incidentally discovered in 5% of CT scans. In 2013/2014, 81 million CT examinations were undertaken in the USA and 5 million in the UK. However, uncertainty remains around the optimal imaging approach for diagnosing malignancy. We aimed to review the evidence on the accuracy of imaging tests for differentiating malignant from benign adrenal masses.

DESIGN

A systematic review and meta-analysis was conducted.

METHODS

We searched MEDLINE, EMBASE, Cochrane CENTRAL Register of Controlled Trials, Science Citation Index, Conference Proceedings Citation Index, and ZETOC (January 1990 to August 2015). We included studies evaluating the accuracy of CT, MRI, or (18)F-fluoro-deoxyglucose (FDG)-PET compared with an adequate histological or imaging-based follow-up reference standard.

RESULTS

We identified 37 studies suitable for inclusion, after screening 5469 references and 525 full-text articles. Studies evaluated the accuracy of CT (n=16), MRI (n=15), and FDG-PET (n=9) and were generally small and at high or unclear risk of bias. Only 19 studies were eligible for meta-analysis. Limited data suggest that CT density >10HU has high sensitivity for detection of adrenal malignancy in participants with no prior indication for adrenal imaging, that is, masses with ≤10HU are unlikely to be malignant. All other estimates of test performance are based on too small numbers.

CONCLUSIONS

Despite their widespread use in routine assessment, there is insufficient evidence for the diagnostic value of individual imaging tests in distinguishing benign from malignant adrenal masses. Future research is urgently needed and should include prospective test validation studies for imaging and novel diagnostic approaches alongside detailed health economics analysis.