[18F]FDG-PET/CT in prone compared to supine position for optimal axillary staging and treatment in clinically node-positive breast cancer patients with neoadjuvant systemic therapy

Purpose Axillary staging before neoadjuvant systemic therapy in clinically node-positive breast cancer patients with tailored axillary treatment according to the Marking Axillary lymph nodes with radioactive iodine seeds (MARI)-protocol, a protocol developed at the Netherlands Cancer Institute, is performed with [ 18 F] fluorodeoxyglucose (FDG) positron emission tomography and computed tomography (PET/CT). We aimed to assess the value of FDG-PET/CT in prone compared to standard supine position for axillary staging. Methods We selected patients with FDG-PET/CT in supine and prone position who underwent the MARI-protocol. One hour after administration of 3.5 MBq/kg, [ 18 F]FDG-PET was performed with a low-dose prone position CT-thorax followed by a supine whole-body scan. Scans were separately reviewed by two nuclear medicine physicians and categorized by number of FDG-positive axillary lymph nodes (ALNs; cALN