A PET scan can detect possible bone marrow involvement in people with rhabdomyosarcoma as reliably as the bone marrow sampling that has been the standard procedure to date. This was shown in a study by the University Medicine Halle and researchers from the Netherlands, Italy, and the United States, which was published in the Journal of Clinical Oncology. The team analyzed data from over 300 patients. According to the findings, most patients — primarily children and adolescents — could be spared the painful tissue sampling.
Rhabdomyosarcomas are a rare form of cancer; however, the disease is responsible for about 60 percent of all soft-tissue sarcomas in children. Rhabdomyosarcomas are aberrant, malignant forms of muscle tissue. Early detection of bone marrow infiltration by tumor cells is crucial when planning treatment.
“Bone marrow sampling has, until now, been considered the gold standard for determining whether the tumor has spread to a patient’s bone marrow. However, this procedure is painful and only provides information about the situation at the site of the puncture. Patchy bone marrow involvement may therefore be missed,” explains Professor Simone Hettmer, last author of the study and director of the Department for Pediatrics I at University Medicine Halle. Therefore, she collaborated with colleagues from around the world to find alternative options in the field of imaging.
The researchers focused on a method used in nuclear medicine called positron emission tomography (PET), which is already used in several other medical contexts. When combined with weakly radiolabeled sugar molecules, known in scientific terms as FDG, tumors can be made visible. This is because cancer cells have high energy requirements and accumulate the radioactive tracer to a greater extent than healthy cells. A scanner measures the tracer and provides an image of the cancerous tissue in the body. Patients are exposed to only a small amount of radiation.
The study included data from more than 300 people with rhabdomyosarcoma. Half of the patients were between one and ten years old. All patients underwent standard bone marrow sampling and FDG-PET imaging before receiving chemotherapy or undergoing surgery.
The study found the following: Three-quarters of the patients examined had no bone marrow involvement. Among the remaining quarter, both the sampling and FDG-PET imaging indicated bone marrow involvement in around 70 percent of cases, while 30 percent of the positive diagnoses were based solely on FDG-PET imaging. In only one case did the standard sampling procedure alone yield a positive result that was not detected by PET.
The results will have a significant impact on clinical practice: “FDG-PET can detect bone marrow involvement in patients with rhabdomyosarcoma as effectively as bone marrow aspirates or biopsies,” concludes Professor Hettmer.
Based on these findings, the researchers recommend adjusting current diagnostic practices. “In the future, FDG-PET should be the first step. If PET imaging detects no FDG-avid bone marrow foci, sampling would not be necessary,” says Professor Hettmer. The authors also recommend confirming abnormal PET findings with bone marrow sampling or magnetic resonance imaging (MRI). An MRI could also confirm tumor-specific changes in tissue structure in previously identified abnormal areas.
Even though FDG-PET can reliably diagnose actual disease involvement, Hettmer notes that other causes can lead to a positive imaging result. These include injuries or inflammation. Positive FDG-PET findings would thus initially raise a strong suspicion that would need to be verified in order to rule out a misdiagnosis.
“A positive FDG-PET scan is a strong indication of bone marrow involvement but still requires confirmation. Conversely, patients with a negative FDG-PET scan can likely avoid a painful bone marrow biopsy in about three-quarters of cases,” emphasizes Reineke A. Schoot, co-last author and pediatric oncologist at the Princess Máxima Center in Utrecht. “Our study suggests that this approach is truly practice-changing.”
The study was conducted by an international research team. Key participants included University Medicine Halle (Germany), the University of Bologna Hospital (Italy), Indiana University, St. Jude Children's Research Hospital in Memphis (U.S.), the Princess Máxima Center for pediatric oncology (Netherlands), and University Medicine Freiburg (Germany).
Study: Mercolini F. et al. Omitting Bone Marrow Sampling in FDG-Avid Rhabdomyosarcoma With 2-[18F]FDG PET-Negative Marrow: Results From an International Retrospective Study. Journal of Clinical Oncology (2026). doi: 10.1200/JCO-25-03080
Journal of Clinical Oncology
Randomized controlled/clinical trial
People
Omitting Bone Marrow Sampling in FDG-Avid Rhabdomyosarcoma With 2-[18F]FDG PET-Negative Marrow: Results From an International Retrospective Study
24-Aug-2026