[18F]FAPI-04 PET/CT for Detection of Recurrent Breast Cancer after Surgery: a Post Hoc Analysis Comparing [18F]FDG PET/CT.

To compare the diagnostic performance of [18F]FAPI-04 PET/CT with that of [18F]FDG PET/CT in patients with suspected recurrence of breast cancer following surgical treatment. This is a post‑hoc analysis of data from a prospective single-center clinical trial. Patients with clinical suspicion of recurrence of breast cancer after surgery were consecutively enrolled and underwent both [18F]FDG and [18F]FAPI-04 PET/CT. Paired comparisons of sensitivity and accuracy were performed using McNemar’s test. Differences in semi-quantitative parameters, including maximum standardized uptake value (SUVmax) and tumor-to-background ratio (TBR), were assessed using the Wilcoxon signed-rank test. A total of 44 patients with 880 lesions were included, of whom 40 patients (782 lesions) were confirmed to have recurrent disease. Compared with [18F]FDG PET/CT, [18F]FAPI-04 PET/CT showed higher sensitivity and accuracy across most metastatic sites. The differences were most pronounced for lymph node, pleural, and bone metastases, with significantly higher sensitivity (98.7