Value of whole body 18FDG-PET to identify the active site of gestational trophoblastic neoplasia.

OBJECTIVE: To evaluate the usefulness of positron emission tomography with 18-fluorodeoxyglucose ( 18 FDG-PET) in locating residual or relapsed gestational trophoblastic neoplasia (GTN). STUDY DESIGN: The Charing Cross GTN database was screened, and 11 patients who had undergone 18 FDG-PET were identified. A retrospective analysis was conducted to determine the value of this investigation as compared with other imaging modalities in clinical care. RESULTS: All patients had elevated β-human chorionic gonadotropin (β-hCG) at the time of the investigation; none were false positive. In 7 patients the 18 FDG-PET scans correctly confirmed the presence (4 of 7 cases) or absence (3 of 7 cases) of disease sites defined by other imaging investigations. In 2 patients positive PET-guided appropriate surgical resection of lung lesions that appeared of equivocal significance on computed tomography (CT) resulted in β-hCG normalization. One patient had a pulmonary metastasis on CT not considered positive on 18 FDG-PET (false negative). One patient with enlarged mediastinal lymph nodes on CT that were 18 FDG-PET positive also had a vascular uterus on magnetic resonance imaging/Dopper ultrasound that was negative on PET (false negative). Hysterectomy led to hCG normalization and cure. The mediastinal lymph nodes were positive on CT and PET due to sarcoidosis (false positive). Patients with serum hCG levels <10 IU/L could have positive PET scans; that can contribute to patient care. CONCLUSION: 18 FDG-PET can aid in identifying residual disease sites in women relapsing from previously treated GTN. However, careful evaluation in combination with other imaging modalities is required to reduce the risk of false positive and negative results.