Using [F]FDG PET/CT to Identify Optimal Responders to Neoadjuvant Therapy in Breast Cancer-Results from a Prospective Patient Cohort.

: Pathological complete response (pCR) to neoadjuvant chemotherapy (NAC) in breast cancer (BC) is a solid indicator of favourable prognosis, potentially also being useful for more conservative patient management. We aim to explore the potential of [F]FDG PET/CT as a non-invasive method to predict response to NAC. : In this prospective, observational cohort study, we enrolled BC patient candidates for NAC who underwent baseline and preoperative [F]FDG PET/CT. NAC response was determined using final histopathology. PET images were assessed qualitatively and semi-quantitatively, and the findings correlated with NAC response. : In total, 133 BC patients were included. The visual analysis of preoperative PET/CT detected residual disease (RD) with high specificity (>93%) and moderate sensitivity, based on pCR/RD classification and RCB index. Semiquantitative measures (SUVmax, TBR) were significantly higher in non-responders across the classification methods ( < 0.001 for all). : These findings highlight the potential of preoperative [F]FDG PET/CT as a complementary tool for identifying excellent responders to NAC across BC subtypes or response criteria. This could inform personalised treatment and potentially allow for surgery to be omitted in selected patients.