Abstract Accurate pathological response assessment of breast cancer following neoadjuvant therapy (NAT) is clinically critical but lacks robust imaging methods, so this study evaluated the diagnostic accuracy of 18 F-fluorodeoxyglucose (FDG) PET/CT and 68 Ga-fibroblast activation protein inhibitor (FAPI) PET/CT in clinically node positive (cN+) breast cancer patients receiving NAT. This prospective study enrolled pathologically confirmed breast cancer patients who underwent NAT and both PET/CT scans preoperatively. The maximum standardized uptake value (SUVmax) was measured and an optimal 68 Ga-FAPI PET/CT threshold was determined via receiver operating characteristic (ROC) curve analysis. Among 75 patients, 33 (44.0%) achieved pathological complete response (pCR). SUVmax was significantly lower in the ypT0/Tis group compared to the ypT+ group for both 18 F-FDG PET/CT (1.45 ± 0.55 vs. 5.19 ± 4.69, p < 0.001) and 68 Ga-FAPI PET/CT (1.59 ± 1.22 vs. 10.45 ± 8.54, p < 0.001). In the overall cohort, 68 Ga-FAPI PET/CT demonstrated higher sensitivity in detecting residual disease compared to 18 F-FDG PET/CT (0.8 vs. 0.6, p = 0.003), with comparable specificity (0.9 vs. 0.9, p = 1.00). Exploratory subgroup analysis found that 68 Ga-FAPI PET/CT had superior sensitivity compared to 18 F-FDG PET/CT in the hormone receptor-positive (HR + ) group (0.8 vs. 0.6, p = 0.02). These findings show that 68 Ga-FAPI PET/CT outperforms 18 F-FDG PET/CT in identifying residual breast lesions after NAT in cN+ patients, particularly among HR+ patients, which would guide further treatment strategies after NAT.
Zhu et al. (Tue,) studied this question.