Usefulness and clinical application of FDG PET for assessment of early recurrent epithelial ovarian cancer

Abstract

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Objectives: Recurrent ovarian cancer is refractory to treatment in most patients. But some treatments such as platinum-based chemotherapy or secondary cytoreducion may be effective and starting a treatment when tumors still consist of micro foci may contribute to improvement of prognosis. Therefore, the early diagnosis of relapse is important. The aim of this study is to assess the potentials of 18F-fluoro-deoxy-glucose positron emission tomography(FDG-PET) in comparison to conventional imaging modalities and serum tumor marker CA125 level in the assessment of patients with suspected ovarian cancer recurrence.

Methods: FDG-PET was performed in 159 patients (age, 25-78 years) with suspected ovarian cancer recurrence based on CT/MRI findings or serum tumor marker CA125 elevation or other nonspecific findings or symptons, from October 2001 until June 2005, in Nishidai Clinic Diagnostic Imaging Center. The final diagnosis were established in 115 patients by operation/biopsy or clinical follow up for more than 6 months, or other additional conventional imaging procedure. We compared the rate of accurate diagnosis in these 115 cases to result obtained with CT/MRI(which was performed simultaneously with FDG-PET), serum CA125 level, and FDG-PET.

Results: The sensitivity, specificity, positive predictive value, negative predictive value of FDG-PET were 82.2%(60/73), 78.6%(33/42), 87.0%(60/69), 71.7%(33/46), respectively. These values were higher than the corresponding values obtained using CT/MRI or CA125 levels. Asymptomatic elevation of tumor marker CA125 and negative or equivocal findings of CT/MRI was observed by 35 patients, and among these cases, final diagnosis of recurrence were established in 31 patients, and the sensitivity, specificity, positive and negative predictive value of FDG-PET were 87.1%(27/31), 75.0%(3/4), 96.4%(27/28), 42.9%(3/7), respectively. Among 44 patients with normal CA125 levels and negative CT/MRI findings, the relapse of 10 patients turned out while observing passage in 6 months, and the sensitivity, specificity, positive and negative predictive value of FDG-PET were 40.0%(4/10), 79.4%(27/34), 36.4%(4/11), 81.8%(27/33), respectively.

Conclusions: FDG-PET cannot rule out microscopic disease, and it is doubtful whether FDG-PET will replace conventional imaging procedure in suspected ovarian cancer recurrence. However, this data indicated that it is certain that FDG-PET is useful modality for the patients with suspected epithelial ovarian cancer recurrence, and especially for the patients with asymptomatic CA125 elevation and negative/equivocal CT/MRI findings, use of FDG-PET is rational.