PET / CT in the early and differential diagnosis of adrenocortical cancer

The objective of the study was to develop criteria for the early diagnosis and differential diagnosis of adrenocortical cancer (ACC) during positron emission tomography combined with computed tomography (PET / CT) with 18F-fluorodeoxyglucose (18F-FDG).

Materials and methods. Diagnostic tests were performed on a General Electric the Discovery PET / CT 610. After scanning 60–90 minutes after the administration of the radiopharmaceutical, PET-grams were formed showing the distribution of the radiopharmaceutical throughout the body in both physiological and pathological areas. Using software, automatic "fusion" of images obtained on PET and CT scanners was carried out. Initially, a radiologist performed an analysis of structural pathological changes in organs, followed by an assessment of the level of accumulation and determination of CT densitometry of pathological adrenal formations. Subsequently, metabolic activity was determined by the level of SUV (standart uptake value).

Results. A retrospective analysis of PET / CT data with 18F-FDG was performed in 50 patients with adrenal tumor formations. Based on the data studied, all patients were divided into 2 groups: 1st group (n = 21) with a subsequent diagnosis of ACC, 2nd group (n = 29) with benign adrenal neoplasms. The age of the patients was 68 (32–76) years and did not statistically differ in both groups (p ˃0.05). After check up tumor parameters the following results were obtained: the average tumor size in patients of the 1st group was 4.5 Ѓ} 0.75 cm, of the 2nd group – 4.9 Ѓ} 1.1 cm, no significant difference was found (p ˃0.05). The diagnostic model obtained by constructing and subsequent analysis of the ROC curve of the SUV level in patients with malignant and benign neoplasms of the adrenal glands showed a high quality model with a sesitivity of 90 %, specificity of 95 % (area under the ROC curve (AUC) 0.93 at p <0.0001 (z = 27.37)) and a cut-off point of 3. When studying CT densitometric parameters of a tumor in patients of the 1st and 2nd groups, a direct correlation relationship between these parameters and the diagnosis of malignant lesions was also obtained (Rs = 0.67; coefficient τ Kendall 0.64; p = 0.001). Interpretation of the results of the ROC analysis of the tumor density level (CT density in Hounsfield units (HU)) in patients of the 1st and 2nd groups showed 80 % sensitivity and 90 % specificity (AUC 0.89; p <0.0001) with clipping point equal to 10 HU.

Conclusion. Obtaining integral information on the SUV level together with the measurement of CT density during PET / CT with 18F-FDG is one of the most modern diagnostic methods that allow both diagnostics and differential diagnosis of ACC in the early stages of the pathological process. The above factors currently indicate the high diagnostic value of PET / CT with 18F-FDG and the priority nature of this study in cases of suspected ACC in patients with adrenal neoplasms of 1–5 cm in size.

adrenocortical cancer, SUV, PET / CT, adrenal gland neoplasm, 18F-fluorodeoxyglucose

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