EUS FNA of Altered Left Adrenal Gland Morphology Suggests Amending CT and PET-CT Attenuation Threshold Values That Predict Malignancy

Abstract

Introduction: In the setting of an extra-adrenal malignancy, it is a recognized clinical challenge to try and distinguish a benign adrenal mass from a metastatic deposit. Current non-invasive diagnostic tools for adrenal gland evaluation include CT, MRI, PET and PET-CT. Diagnostic interpretative error can occur as evaluations rarely have complete cytologic or histologic correlation for concordance purposes. Aims: To establish the performance characteristics of non-contrast CT attenuation values (Hounsfield units-HU) and the optimal PET-CT maximum standard uptake value (SUV<sub>max</sub>) for predicting adrenal malignancy when correlated with adrenal gland endoscopic ultrasound fine needle aspiration (EUS FNA) cytology results. Methods: A prospectively maintained EUS database was reviewed to identify consecutive patients who underwent a left adrenal gland FNA. Non-contrast CT attenuation values and SUV<sub>max</sub> scores were calculated. EUS FNA cytology results were used as the reference standard for determining the presence of benign versus malignant adrenal gland status. Results: Sixty-two patients (69 ± 11 years) underwent adrenal EUS FNA, 34 (54.8%) of whom had a clinically suspected or established extra-adrenal malignancy. Non-invasive imaging was suggestive of abnormal adrenal morphology or altered PET-CT FDG activity in 45 (72.6%) patients. Elevated attenuation values (≥10 HU) by non-enhanced CT had a sensitivity and specificity of 100% and 34.6%, respectively. The SUV<sub>max</sub> for malignant altered morphology was significantly higher than that for benign lesions [(8.5 ± 3.1 vs 3.3 ± 0.7; (p = 0.0001)]. ROC curve analysis indicated that an optimum cutoff SUV<sub>max</sub> of ≥4.1 (AUC 0.92) yielded the best power distinction for malignancy with a sensitivity and specificity of 89% and 100%. Conclusion: When evaluating altered adrenal morphology by non-invasive methods, the performance characteristics of elevated CT attenuation values are suboptimal. But by adopting a SUV<sub>max</sub> cut-off value of ≥4.1 could potentially improve such characteristics to detect malignancy