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Usefulness of 18F-FDG PET in the Management of Recurrent Ovarian Cancer Patients with Unexplained Tumor Marker CA 125 Elevation: A Preliminary Report

Purpose: This prospective study was to evaluate the adding value of FDG PET in ovarian cancer patients with unexplained serum CA 125 elevation after primary definitive treatment. Methods: From June 2001 to August 2006, 29 ovarian cancer patients with 31 scans were enrolled. Of the 31 scan, 30 were from PET and one was from PET/CT. The definition of unexplained tumor marker elevation was either with serum tumor marker of CA 125 increased with doubling and at least once ＞35 U/ml, or CA 125 elevation with twice ＞35 U/ml. All had no obvious evidence of disease by standard surveillance protocol, including whole body CT. The gold standard of disease status was determined by histopathology and/or clinical follow up for at least 6 months. The management impact of PET was on scan-based. The primary end point was the diagnostic efficacy and the secondary end point was the clinical impact after PET scan. Results: The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of PET for relapse detection were 84.6%, 40.0%, 91.7%, 33.3% and 77.4%, respectively. On a PET scan-based analysis, the positive impact was 77.4% (24/31) and 22.6% (7/31) for negative impact. Of the positive impacts, 91.7% (22/24) were confirmed to have disease recurrence and 8.3% (2/24) were to rule out falsely CA-125 elevation. Of the negative impacts, 42.9% (3/7) had falsely positive and 57.1% (4/7) were falsely negative. Conclusion: For ovarian cancer patients with unexplained serum CA 125 elevation, the PPV of PET was high though the negative predictive value was limited. The positive impacts of PET were two. One was to find out the recurrent lesions and the other was to rule out the falsely CA 125 elevation. The negative impacts of PET were also two. One was physiological uptake at bowel, which may have chances to overcome by PET/CT and the other was small recurrent diseases with largest size of equal or under 6 mm in diameter.