Retrospective study of omitting bone marrow sampling in FDG-avid rhabdomyosarcoma with FDG PET-negative marrow results
Detection of bone marrow disease is a major component of rhabdomyosarcoma (RMS) staging, with bilateral bone marrow aspirates/biopsies (BMAB) from the iliac crests considered the diagnostic gold standard. A multinational retrospective study evaluated 2-18F-labeled fluorodeoxyglucose positron emission tomography/computed tomography ([18F]FDG PET/CT) or PET/magnetic resonance imaging (MRI) for detection of bone marrow disease in RMS. Patients (children and adolescents) were recruited at 18 centers across Europe and North America. PET imaging and BMAB were performed before chemotherapy and tumor resection in 301 patients with FDG-avid RMS. Bone marrow metastases were detected by PET and BMAB in 54 patients, by PET only in 24 patients, and by BMAB only in one patient, translating into 98% sensitivity and 90% specifity for PET in detecting bone marrow metastases when BMAB was considered as gold standard. FDG-avid marrow disease was patchy (1-5 foci) in one third of cases. Patients with marrow disease indicated by PET and BMAB had more FDG-avid bone marrow foci, more metastatic sites, and worse survival than those with marrow disease indicated by PET only, suggesting more advanced disease stages. The authors conclude that bone marrow sampling may be omitted in patients without evidence of FDG-avid bone marrow disease by PET. If there are FDG-avid bone marrow lesions, further investigation by MRI and/or biopsy should be considered (graphical abstract).