Clinical utility of positron emission tomography/computed tomography in the evaluation of suspected recurrent ovarian cancer in the setting of normal CA-125 levels

Objectives: This study was conducted to estimate the accuracy of [ ¹⁸F]-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) as compared with contrast-enhanced CT (CECT) in detecting cancer in patients who have normal cancer antigen (CA)-125 (<35 U/dL) but are suspected of having a recurrent disease based on clinical symptoms. Methods: We retrospectively reviewed the records of patients who had undergone primary cytoreductive surgery and subsequently underwent CECT and FDG-PET/CT for suspected recurrence. [¹⁸F]-fluorodeoxyglucose positron emission tomography/computed tomography and CECT interpretation to evaluate a recurrent disease was carried out independently by 2 experienced radiologists who were blinded to the final diagnosis for the suspected recurrence. Long-term follow-up imaging (12 months) and biopsy reports were used to assess the true status of the suspected recurrence seen on FDG-PET/CT or CECT. Sensitivity and specificity of all modalities were estimated. McNemar test was used to compare pairs of modalities. All tests were 2-sided, and P ≤ 0.05 was considered statistically significant. Results: Sixty-six patients met the eligibility criteria for inclusion in our analysis. Fifty-eight percent (18/31) and 54% (17/31) of the patients with normal CA-125 levels had evidence of a recurrent disease on FDG-PET/CT and CECT, respectively. Thirty-one percent (6/19) of the patients with no indication of cancer on CECT had evidence of disease on FDG-PET/CT images, which was supported by pathological proof. Conclusion: [¹⁸F]-Fluorodeoxyglucose positron emission tomography/computed tomography is capable of detecting ovarian cancer recurrence in symptomatic patients with normal CA-125 levels and, in this setting, has slightly better sensitivity than CECT and can be considered as the frontline modality for all such patients.