Whole body positron emission tomography (PET) for the detection of residual disease in gestational trophoblastic tumors (GTTs)

Abstract

5109 Background: GTTs including invasive mole and choriocarcinoma are usually cured with chemotherapy assessed by a normalisation of the pregnancy hormone hCG. Relapses detected by a rising hCG can be cured by subsequent surgery/chemotherapy. Identification of the active site of recurrence for potential surgical resection can be difficult, particularly when there are mutliple lesions seen on CT/MRI. Whole-body 18fluorodeoxyglucose (18FDG)-PET may provide a solution to this problem and its value is examined here. Methods: The Charing Cross GTT database was screened and 9 patients were identified post- initial chemotherapy with rising or persistently elevated hCG who underwent CT/MRI and whole body 18FDG-PET to identify potential sites of active disease. The subsequent effect of surgery and or chemotherapy was assessed by the fall in hCG levels and the value of 18FDG-PET in management was determined. Results: 3 patients with residual lesions on CT/MRI which were active on PET, subsequently had surgery alone resulting in normalisation of hCG levels. One patient had a normal CT/MRI, but was PET positive in the lungs. The affected lung area was resected and the hCG normalised. Two patients had CT/MRI lesions not positive on PET. Further chemotherapy led to normalisation of hCG and CT/MRI. One patient with a lesion seen on CT and PET had resolution of these changes with chemotherapy. The 8th patient had a persistently raised hCG post-chemotherapy with a normal CT/MRI but was PET positive in the stomach, which resolved with chemotherapy. The 9th patient had a persistently raised serum hCG between 20–30iu/l, despite no lesion on CT/MRI or PET, and has remained well off treatment for 24 months. Conclusion: We report the largest series to date of the use FDG- PET scanning in GTT. PET scanning can be useful for confirming sites of active disease seen as lesions on CT/MRI scans. In two cases PET scanning found sites of disease not seen on conventional imaging. No significant financial relationships to disclose.