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

Aim: To determine the additional value of [(18)F]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=1), and granulosa cell tumor (n=1). All patients underwent [(18)F]FDG-PET and contrast enhanced CT examinations, within 30 days of the completion of chemotherapic treatment. [(18)F]FDG-PET images were interpreted with the knowledge of CT findings (PET+CT); conversely, CT images were evaluated with no knowledge of the [(18)F]FDG-PET results. Within 7 day of imaging studies, 2(nd)-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.