Increased lesion detectability in patients with locally advanced breast cancer—A pilot study using dynamic whole-body [18F]FDG PET/CT

Background Accurate diagnosis of axillary lymph node (ALN) metastases is essential for prognosis and treatment planning in breast cancer. Evaluation of ALN is done by ultrasound, which is limited by inter-operator variability, and by sentinel lymph node biopsy and/or ALN dissection, none of which are without risks and/or long-term complications. It is known that conventional 2-deoxy-2-[ 18 F]fluoro-D-glucose ([ 18 F]FDG) positron emission tomography/computed tomography (PET/CT) has limited sensitivity for ALN metastases. However, a recently developed dynamic whole-body (D-WB) [ 18 F]FDG PET/CT scanning protocol, allowing for imaging of tissue [ 18 F]FDG metabolic rate (MR FDG ), has been shown to have the potential to increase lesion detectability. The study purpose was to examine detectability of malignant lesions in D-WB [ 18 F]FDG PET/CT compared to conventional [ 18 F]FDG PET/CT. Results This study prospectively included ten women with locally advanced breast cancer who were referred for an [ 18 F]FDG PET/CT as part of their diagnostic work-up. They all underwent D-WB [ 18 F]FDG PET/CT, consisting of a 6 min single bed dynamic scan over the chest region started at the time of tracer injection, a 64 min dynamic WB PET scan consisting of 16 continuous bed motion passes, and finally a contrast-enhanced CT scan, with generation of MR FDG parametric images. Lesion visibility was assessed by tumor-to-background and contrast-to-noise ratios using volumes of interest isocontouring tumors with a set limit of 50% of SUVmax and background volumes placed in the vicinity of tumors. Lesion visibility was best in the MR FDG images, with target-to-background values 2.28 (95% CI: 2.04–2.54) times higher than target-to-background values in SUV images, and contrast-to-noise values 1.23 (95% CI: 1.12–1.35) times higher than contrast-to-noise values in SUV images. Furthermore, five imaging experts visually assessed the images and three additional suspicious lesions were found in the MR FDG images compared to SUV images; one suspicious ALN, one suspicious parasternal lymph node, and one suspicious lesion located in the pelvic bone. Conclusions D-WB [ 18 F]FDG PET/CT with MR FDG images show potential for improved lesion detectability compared to conventional SUV images in locally advanced breast cancer. Further validation in larger cohorts is needed. Clinical trial registration The trial is registered in clinicaltrials.gov, NCT05110443, https://www.clinicaltrials.gov/study/N