[18F]Fluorthanatrace PET in Ovarian Cancer: Comparison with [18F]FDG PET, Lesion Location, Tumor Grade, and Breast Cancer Gene Mutation Status

Poly(adenosine diphosphate–ribose) polymerase-1 (PARP1) inhibitors have improved ovarian cancer treatment outcomes. However, clinical response remains heterogeneous. Existing biomarkers, mainly breast cancer susceptibility genes 1 and 2 (BRCA1/2), are suboptimal. New tools are needed to guide patient selection. In this study, [¹⁸F]fluorthanatrace ([¹⁸F]FTT), a PET radiotracer for imaging PARP1, was compared with [¹⁸F]FDG and tumor features commonly assessed in ovarian cancer. Methods: Subjects with epithelial ovarian cancer underwent both [¹⁸F]FTT and [¹⁸F]FDG PET before new oncologic treatment. The SUV_max of [¹⁸F]FTT and [¹⁸F]FDG was compared between lesions. [¹⁸F]FTT SUV_max was compared with tumor location, tumor grade, and germline or somatic BRCA1/2 status. Linear mixed models were fitted to identify subject-level differences. Results: Fifty-five lesions were identified in 14 subjects. No correlation was found between [¹⁸F]FTT SUV_max and [¹⁸F]FDG SUV_max per lesion, supporting distinct molecular targets. [¹⁸F]FTT uptake varied widely across lesions, with no significant differences between mean SUV_max and tumor location, grade, or BRCA1/2 status. Conclusion: Our findings suggest that [¹⁸F]FTT PET may provide unique information on ovarian cancer distinct from [¹⁸F]FDG PET and commonly assessed tumor features. Our results imply a wide range of PARP1 expression in the studied ovarian tumors not explained by [¹⁸F]FDG PET, location, grade, or mutational status.