Lesion Detection and Uptake Patterns of [¹⁸F]F-ATD001 PET/CT and [¹⁸F]FDG PET/CT in Triple-Negative Breast Cancer

In triple-negative breast cancer (TNBC), the upregulation of poly(adenosine disphosphate-ribose) polymerase (PARP) has afforded an attractive therapeutic target with PARP inhibitors. Improved survival outcomes associated with PARP inhibitors as either monotherapy or adjuvant therapy have been demonstrated in various clinical trials. Because PARP expression may vary between lesions, whole-body PARP-targeted imaging may complement standard-of-care [¹⁸F]FDG PET/CT. [¹⁸F]F-ATD001, a radiolabeled olaparib PET tracer, is a noninvasive biomarker of in vivo PARP expression. We compared the uptake characteristics and lesion detection patterns of [¹⁸F]F-ATD001 PET/CT with those of [¹⁸F]FDG PET/CT in patients with TNBC. Methods: Consenting participants aged 18 y or older with histologically confirmed TNBC and measurable disease on [¹⁸F]FDG PET/CT were included. Whole-body PET/CT was performed 60 min after intravenous injection of [¹⁸F]F-ATD001. Semiquantitative (SUV_max and SUV_mean) analysis and numeric counting of lesions at different sites (primary, lymph node, viscera, and skeleton) were performed for both [¹⁸F]FDG PET/CT and [¹⁸F]F-ATD001 PET/CT images. Site-level detection rates were compared between tracers, and correlations of semiquantitative parameters were assessed. Results: Thirty-seven women with histologically confirmed TNBC underwent both [¹⁸F]FDG PET/CT and [¹⁸F]F-ATD001 PET/CT. The mean ± SD age was 45.3 ± 11.73 y (range, 23-75 y). Most patients (32/37, 86.5%) had infiltrating ductal carcinoma of no special subtype. Semiquantitative parameters for [¹⁸F]F-ATD001 were substantially lower than the corresponding values for [¹⁸F]FDG across all malignant sites, with a median SUV_max of 3.45 versus 17.63 in primary lesions and 3.88 versus 10.25 in lymph nodes, respectively. Moderate correlation was observed for SUV_max and SUV_mean in primary lesions (Spearman ρ = 0.39 and 0.54, respectively), whereas correlation was weak at other sites. No statistically significant site-level differences in lesion detection rates were observed between [¹⁸F]FDG PET/CT and [¹⁸F]F-ATD001 PET/CT. Conclusion: In this study of patients with TNBC, no statistically significant site-level differences in lesion detection rates were observed between [¹⁸F]F-ATD001 PET/CT and [¹⁸F]FDG PET/CT. Despite lower uptake values on [¹⁸F]F-ATD001 PET/CT, moderate correlation was observed in primary lesions, with weaker correlation at other sites. These findings suggest that [¹⁸F]F-ATD001 PET/CT may have a complementary role with [¹⁸F]FDG PET/CT in the evaluation of patients with TNBC.