RT Journal Article SR Electronic T1 18F-FDG PET/CT in Erdheim–Chester Disease: Imaging Findings and Potential BRAF Mutation Biomarker JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 774 OP 779 DO 10.2967/jnumed.117.200741 VO 59 IS 5 A1 Young, Jason R. A1 Johnson, Geoffrey B. A1 Murphy, Robert C. A1 Go, Ronald S. A1 Broski, Stephen M. YR 2018 UL http://jnm.snmjournals.org/content/59/5/774.abstract AB The purpose of this study was to evaluate 18F-FDG PET/CT for the diagnosis, management, and treatment of Erdheim–Chester disease (ECD). Methods: Our institutional database (2007–2017) was retrospectively reviewed for patients with pathologically proven ECD. A chart review yielded demographics, clinical information, and 5 categories of clinical impact. Two radiologists in consensus interpreted the images. Imaging findings were correlated with clinical data. Results: Seventy-one 18F-FDG PET/CT examinations were performed for 32 patients. The average SUVmax of the most active disease site was 9.2 (SD, 6.1). The most common sites involved were the skeleton (90.6% of patients, including 47% with axial and pelvic skeletal involvement), kidneys (81.3%), and central nervous system (CNS) (46.9%). Twenty-six patients were tested for a proto-oncogene B-Raf V600E (BRAF) mutation (18 had the mutation and 8 did not). The presence of a BRAF mutation was associated with 18F-FDG–avid CNS disease (P = 0.0357), higher SUVmax (P = 0.0044), and greater mortality (P = 0.0215). The presence of CNS disease had 88% specificity and a 92% positive predictive value for predicting the presence of a BRAF mutation. PET/CT examination results influenced patient management in 48% of cases (34/71). Conclusion: 18F-FDG PET/CT results may act as a biomarker for the presence of a BRAF mutation, aid in establishing a diagnosis, guide biopsies, and gauge the treatment response in ECD patients. Axial and pelvic skeletal involvement is greater than previously reported.