Abstract
PURPOSE: This study evaluates the clinical impact of routine FDG-PET/CT on locoregional treatment in a large cohort of breast cancer patients scheduled for preoperative systemic therapy (PST). METHODS: Patients scheduled for PST were identified from a retrospective database between 2011 and 2020 at our hospital. All patients underwent staging by FDG-PET/CT prior to PST. The rate of regional upstaging by FDG-PET/CT compared to initial locoregional staging was assessed, as well as its implications on surgical and radiotherapeutic management. Logistic regression analysis was used to evaluate the correlation between clinical characteristics and regional upstaging by FDG-PET/CT. RESULTS: Among 1228 eligible patients, FDG-PET/CT detected additional regional lymph node involvement in 145 patients (12 %). This resulted in treatment modifications for 140 patients (11 %), including changes to the axillary surgical approach in 27 patients (2 %), and adjustments to the postoperative radiation therapy plans in 115 patients (9 %). The majority of these modifications occurred in patients initially staged as cN1(1-3) (92/140). Clinical T stage was significantly associated with regional upstaging by FDG-PET/CT. CONCLUSION: FDG-PET/CT staging before PST frequently identifies additional regional lymph node involvement, significantly altering locoregional treatment strategies in the majority.