ABSTRACT
PURPOSE: Patients treated for ovarian cancer are usually referred for 2-deoxy-2-[18F]fluoro-D-glucose positron emission tomography/computed tomography (FDG PET/CT) in case of increased Carcinoma Antigen 125 (CA125) but negative conventional imaging. However, there is not enough in the literature to support the value of FDG PET/CT in this context. This study aimed to assess role of FDG PET/CT in a cohort of patients with treated ovarian cancer and correlate the results with serum levels of CA125. PROCEDURES: We retrospectively studied 175 patients, mean age 65.2 years (range 24-88 years) who had radical treatment for ovarian cancer (chemotherapy, surgery or combination). The patients had a standard FDG PET/CT and measurement of serum CA125 within a month of the scan. PET/CT was considered positive if demonstrated areas of abnormally increased metabolic activity unrelated to physiological distribution, on the basis of a visual analysis. The results of PET/CT imaging were compared to the level of CA125, and receiver operating characteristic (ROC) curves were plotted and area-under-the curve (AUC) statistics were computed. Cytologic or histologic data or clinical and imaging follow-up were taken as gold standard. RESULTS: Patients were divided into five groups based on CA125 values. The average level of CA125 was 107.7 (range 3-867, SD 166.1). PET/CT was positive in 125/175 cases (71.4%), mean value of CA125 132.2 (SD 182.9) and negative in 50/175 (28.6%), mean value of CA125 46.4 (SD 89.3). In descriptive ROC analyses, the discriminatory power of this marker was relatively high (AUC statistics 0.77, range = 0.703-0.8). The optimal cut-off point of CA125 after treatment to reflect active disease on PET/CT was 18 U/mL achieving a detection rate of 85.6%. There was no relation between PET/CT negativity and the histological type of the tumor. CONCLUSION: PET/CT was able to detect active disease at relatively low levels of CA125, thereby facilitating the early diagnosis of recurrence or residual disease. Also in patients with low CA125 levels (<30), PET/CT had a relatively high detection rate (53%). According to our preliminary results, the use of FDG PET/CT in this setting is justified even with low serum CA125 levels.
