May it be a new parameter of 18F-FDG PET/CT for differentiating between benign and malignant adrenal lesions: "Adrenal Densitometabolic Index (ADMI)".

Objective: This study evaluates the diagnostic importance of a new parameter consisting of the densitometric and metabolic properties of the lesion measured by 18F-FDG PET/CT in differentiating between benign and malignant adrenal lesions in cancer patients.

Material and methods: We evaluated PET/CT parameters of adrenal lesions of patients between 2017 and 2019. A new parameter, "Adrenal Dansitometabolic index (ADMI)," was investigated. Additionally, SUVmax, tumor-to-liver ratio (T/LR), Hounsfield Units (HU), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) of adrenal lesions were analyzed. Logistic regression analyses were conducted to identify the most predictive parameter for malignant lesions.

Results: Two hundred and four adrenal lesions underwent PET/CT for tumor evaluation. Based on ROC analysis, ADMI > 9.5, a SUVmax > 4.15, a T/L SUVmax ratio > 1.7, an attenuation value > 21.75 HU, a TLG > 14.61 and a MTV > 4.5 were chosen as the optimal cut-off values for differentiating malignant from benign lesions. ADMI, SUVmax, and T/L ratio demonstrated similarly high diagnostic performance (AUC values: 0.993, 0.992 and 0.988 (P = .000), respectively). ADMI exhibited the highest sensitivity and negative predictive value. A multivariate logistic regression analysis revealed that both ADMI and T/L ratio serve as independent prognostic factors for malignancy (P = .001 and P = .003, respectively).

Conclusion: ADMI, effectively distinguishes benign from malignant. This technique may facilitate investigations of the adrenal lesions to clinical outcomes but needs further large series studies.