The role of ¹⁸F-fluorodeoxyglucose positron emission tomography in gestational trophoblastic tumours: A pilot study

Purpose: We conducted a pilot trial to evaluate the value of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET) in gestational trophoblastic tumours (GTTs). Methods: Patients with placental site trophoblastic tumour (PSTT), high-risk GTT (World Health Organisation score ≥8, disease onset at postpartum or greater than 6 months after antecedent pregnancy), metastatic GTT, recurrent/resistant GTT after chemotherapy, or post-molar GTT with unexplained abnormal β-hCG regression and patients undergoing re-evaluation after salvage treatment were enrolled. PET was undertaken within 1 week after computed tomography (CT). Clinical impacts of additional PET were determined on a scan basis. Results: A total of 14 patients were recruited. Sixteen PET scans were performed, with one patient having three serial studies. Benefits of additional PET were seen in 7 of 16 (43.8%) scans; these benefits included disclosure of chemotherapy-resistant lesions (n=2), exclusion of false-positive CT lesions (n=1), detection of an additional lesion not found by conventional imaging (n=1) in high-risk GTT at the start of primary chemotherapy, and confirmation of complete response to treatment for PSTT or to salvage therapy for recurrent/resistant GTT (n=3). On the other hand, in two instances there were false-negative PET findings, six scans yielded no benefit, and one showed an indeterminate lesion. Conclusion: Our preliminary results suggest that ¹⁸F-FDG PET is potentially useful in selected patients with GTT by providing precise mapping of metastases and tumour extent upfront, by monitoring treatment response and by localising viable tumours after chemotherapy. A larger study is necessary to further define the role of ¹⁸F-FDG PET in GTT.