Role of super(18)F-FDG PET in the management of gestational trophoblastic neoplasia

Purpose: Gestational trophoblastic neoplasia (GTN) is a rare and aggressive tumour that is usually sensitive to chemotherapy. The usefulness of conventional imaging modalities in evaluating treatment response is limited, mainly due to the difficulty in differentiating between residual tumour tissue and necrosis. The aim of the present study was to evaluate the role of FDG PET or PET/CT in primary staging and in monitoring treatment efficacy. The effect of FDG PET and combined PET/CT on the management of patients with GTN was also evaluated comparing the differences between standard treatments based on conventional imaging and alternative treatments based on PET. Methods: This retrospective study included 41 patients with GTN referred to San Raffaele Hospital between 2002 and 2010. All patients were studied by either PET or PET/CT in addition to conventional imaging. Of the 41 patients, 38 were evaluated for primary staging of GTN and 3 patients for chemotherapy resistance after first-line chemotherapy performed in other Institutions. To validate the PET data, PET and PET/CT findings were compared with those from conventional imaging, including transvaginal ultrasonography (TV-US) in those with uterine disease, CT and chest plain radiography in those with lung disease and whole-body CT in those with systemic metastases. Conventional imaging was considered positive for the presence of uterine disease and/or metastases when abnormal findings relating to GTN were reported. PET and PET/CT were considered concordant with conventional imaging when metabolic active disease was detected at the sites corresponding to the pathological findings on conventional imaging. In addition, in 12 of the 41 patients showing extrauterine disease, FDG PET/CT was repeated to monitor treatment efficacy, in 8 after normalization of beta human chorionic gonadotropin ( beta HCG) and in 4 with beta HCG resistance. In some patients, PET or PET/CT findings led to an alternative nonconventional treatment, and this was considered a change in patient management for the study analysis. Results: When compared to TV-US, chest radiography and CT for staging, PET showed a concordance in 91 %, 84 % and 81 % of patients, respectively. In 8 of the 41 patients with extrauterine disease during staging, PET/CT showed a complete response to therapy after beta HCG normalization. PET and PET/CT identified the sites of persistent disease in all seven high-risk patients with beta HCG resistance, of whom fo