Advanced ovarian carcinoma: Usefulness of [18F]FDG-PET in combination with CT for lesion detection after primary treatment

Aim. To determine the additional value of [¹⁸F]FDG-PET in combination with computed tomography (CT) over CT used alone, for evaluating ovarian cancer patients after primary treatment. Methods. Twenty-five women (mean age: 53.6 years) had primary debulking surgery followed by chemotherapy for histologically proven ovarian carcinoma. At initial diagnosis, the tumor types were papillary serous adenocarcinoma (n=20), endometroid carcinoma (n=3), mixed mullerian tumor (n=l), and granulosa cell tumor (n=1). All patients underwent [¹⁸F]FDG-PET and contrast enhanced CT examinations, within 30 days of the completion of chemotherapic treatment. [¹⁸F]FDG-PET images were interpreted with the knowledge of CT findings (PET+CT); conversely, CT images were evaluated with no knowledge of the [¹⁸F]FDG-PET results. Within 7 day of imaging studies, 2nd-look laparoscopy (n=7) or laparotomy (n=18) was performed for histological confirmation. In all cases, imaging findings were then correlated with results of histopathologic examination. Results. Of the 23 neoplastic viable lesions, all histologically confirmed, 16 could be detected by CT alone and 19 by PET+CT. An inflammatory lymph-node was misdiagnosed as viable tumor with both PET+CT and CT alone; an area of scar tissue in the presacral region was also misinterpreted as malignant tissue with CT alone. Overall lesion-based sensitivity, specificity and accuracy in assessing focal areas of residual tumor were as follows: 69.56%, 83.33%, 74.28% for CT, and 82.60%, 91.67%, 85.71% for PET+CT. The negative predictive value of PET+CT was markedly higher (73.33%), compared to that of CT alone (58.82%). Conclusion. PET used in combination with CT allows to accurately assess tumor response. A major advantage of PET+CT over CT alone is in excluding the presence of residual viable lesions after treatment.