Does the pretreatment tumor sampling location correspond with metabolic activity on 18F-FDG PET/CT in breast cancer patients scheduled for neoadjuvant chemotherapy?

Purpose: To define the correlation between the core biopsy location and the area with highest metabolic activity on 18F-FDG PET/CT in stage II–III breast cancer patients before neoadjuvant chemotherapy. Also, we would like to select a subgroup of patients in which PET/CT information may optimize tumor sampling. Methods: A PET/CT in prone position was acquired in 199 patients with 203 tumors. The distance and relative difference in standardized uptake value (SUV) between core biopsy localization (indicated by a marker) and area with highest degree of FDG uptake were evaluated. A distance ≥2 cm and a relative difference in SUV ≥25% were considered clinically relevant and a combination of both was defined as non-correspondence. Non-correspondence for different tumor characteristics (TNM stage, lesion morphology on MRI and PET/CT, histology, subtype, grade, and Ki-67) was assessed. Results: Non-correspondence was found in 28 (14%) of 203 tumors. Non-correspondence was significantly associated with T-stage, lesion morphology on MRI and PET/CT, tumor diameter, and histologic type. It was more often seen in tumors with a higher T-stage (p = 0.028), diffuse (non-mass) and multifocal tumors on MRI (p = 0.001), diffuse and multifocal tumors on PET/CT (p < 0.001), tumors >3 cm (p < 0.001), and lobular carcinomas (p < 0.001). No association was found with other features. Conclusion: Non-correspondence between the core biopsy location and area with highest FDG uptake is regularly seen in stage II–III breast cancer patients. PET/CT information and possibly FDG-guided biopsies are most likely to improve pretreatment tumor sampling in tumors >3 cm, lobular carcinomas, and diffuse and multifocal tumors