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

Abstract

Context[18F]FDG PET/CT improves adrenal tumour characterization. However, there is still no consensus regarding the optimal imaging biomarkers of malignancy.ObjectivesTo assess the performance of Tumour standardized uptake value (SUV)max:Liver SUVmax for malignancy‐risk and to build and evaluate a prediction model.Design/MethodsThe cohort consisted of consecutive patients with adrenal masses evaluated by [18F]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 SUVmax:Liver SUVmax (>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).ResultsSixty‐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 [18F]FDG uptake. CT‐derived anthropometric parameters did not differ between benign and malignant masses. A tumour SUVmax:Liver SUVmax > 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 SUVmax ratio for malignancy‐risk was validated and provides a complementary approach to the ratio.ConclusionsTumour SUVmax:Liver SUVmax 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.

Diagnostic accuracy of 18F-FDG PET/TC for the characterization of adrenal lesions in a heterogeneous population

“…This cut-off applied to our entire population showed Sn, Sp, PPV, and NPV of 100%, 87%, 73%, and 100% respectively, con rming the two previous researches [1,22]. The proposed 1.5 cut-off in our population agreed with the diagnosis according to the gold standard in most of the cases (38 cases; 90.5%); the 4 discordant lesions with a SUVratio > 1.5 and a non-malignant diagnosis were 2 non-functioning adenomas, 1 hyperplasia, and 1 pheochromocytoma.…”

“…As a second step, we tried to calculate the best cut-off in our population, reaching the same results of previous studies [1,22]. In particular, the best cut off for SUVratio was 1.55 in the whole population (with or without pheochromocytomas), and 1.49 excluding patients with metastases and pheochromocytomas.…”

“…The cut-off performance has been re-evaluated in 64 patients [22], being con rmed to be used in a predictive model of malignancy.…”

“…The use of tumor-to-liver maximum standardized uptake values (SUVratio) was found to be more accurate than visual analysis in the differentiation between benign and malignant lesions, with the best threshold value that varies across studies. In a prospective multicentric study, a SUVratio > 1.5 was associated with malignancy with sensitivity, speci city, positive predictive value (PPV), negative predictive value (NPV), and accuracy of 86.7%, 86.1%, 56.5%, 96.9% and 86.2%, respectively [1,22]. Although this cut-off value is useful, some adrenal lesions could be still misdiagnosed [24][25][26][27][28].…”

Optimal and novel imaging of the adrenal glands

“…Using a ratio of adrenal tumor standardized uptake value maximum (SUV max ) to liver SUV max newer studies have demonstrated promising results. For instance, a recent study assessed this new biomarker in 64 patients [45]. Using a cutoff of 1.5 the tumor to liver SUV max demonstrated a sensitivity of 90% and specificity of 93% in identifying malignant lesions.…”