PAGET'S DISEASE OF THE BONE FOUND INCIDENTALLY ON F-18 FDG PET/CT: CLINICAL SIGNIFICANCE AND DIFFERENTIAL DIAGNOSTIC CRITERIA

Abstract

Background: Paget Disease (PD) is usually asymptomatic and discovered incidentally, it is known that it is exhibited low to high grade increased F-18 FDG uptake.

Aim: In this study, we investigated the distinguishability of FDG PET/CT in incidental PD cases from other bone diseases and at different stages of the disease.

Patients and methods: In this cross-sectional, descriptive study, "Paget" identification associated with PET/CT reports was found in 69 of 18,119 studies (~3.8%). Of the 45 patients (33 males and 12 females) eligible for inclusion in the study, 35.6% had monostotic and 64.4% had polyostotic disease (p>0.5). There was no statistically significant difference in biochemical parameters between groups.

Results: According to the radiological appearance of the patients, 36 were in the mixed stage and 9 were in the blastic stage. Only the difference in ALP and creatinine values between the groups was statistically significant. SUVmax, SUVmean and HU values were found to be statistically significantly higher in pagetoid bones compared to control bone lesions. For SUVmax for PD bone lesion we found the 2.55 cutoff point with a sensitivity of 91% and a specificity of 84%.

Conclusion: The specific radiological appearance of bone lesions and the evaluation of metabolic activity compared to normal bone seem to help differentiate PD from other lesions. Prospective studies are needed in the differentiation of FDG's disease stage and treatment response evaluation. The ability to differentiate between benign and malignant FDG avid bone lesions in oncological patients' enables appropriate patient management, including avoiding unnecessary additional invasive procedures such as bone biopsy.

Keywords: F-18 FDG PET/CT; Paget disease; incidental bone lesion.

Figure 1

A-B-C: 61-year-old female patient, monostatic PD (SUVmax 11; HU 128) with significant monostatic FGD accumulation in the sacrum (axial CT and PET images and sagittal fusion images). D-E: A 68-year-old male patient was diagnosed with thyroid cancer. It has polyostatic involvement in the thoracolumbar vertebrae, sacrum, right ilium, ischium and pubis, and exhibits low FDG affinity (vertebra SUVmax 3.4 and HU 282, sacrum SUVmax 2 and HU 176, right hemipelvis SUVmax 1.9 and HU 217) (Sagittal and coronal fusion image’). F: A 61-year-old male patient with a head and neck tumor. Polyostatic PD with involvement of both ilium, left ischium and pubis, entire left femur, and right femoral head and neck. There is increased FDG accumulation in the left femur (SUVmax 3.6 and HU 319).

Figure 2

Receiver-operating curve analysis. Cut-off of 2.55 for SUVmax, 0.920 for SUVmean and 108.5 for HU yielded sensitivity of 97%, 82, 69 and specificity of 90% (area under curve, 0.936, 0.819, and 0.674, respectively).