By Will Boggs, MD
NEW YORK (Reuters Health) Sep 02 - Many children and adolescents with rhabdomyosarcoma can be spared bone marrow aspiration and biopsy if presenting characteristics are used for disease staging, a new report suggests.
Only about 16% of newly diagnosed rhabdomyosarcoma patients present with distant metastases, researchers say. So selecting staging studies according to the risk of metastasis could decrease the number of procedures and their associated sequelae while ensuring accurate staging.
"Clinical and tumor features in children and adolescents with newly diagnosed rhabdomyosarcoma predict the frequency and pattern of distant metastases, allowing for a risk-based approach to initial disease evaluation," Dr. Aaron R. Weiss from Maine Medical Center, Portland, Maine told Reuters Health by email. "This approach avoids unnecessary testing, which carries its own complications, costs, and false-positive findings."
Dr. Weiss and colleagues from the Soft Tissue Sarcoma Committee of the Children's Oncology Group used recursive partitioning analysis on patient data from the Intergroup Rhabdomyosarcoma Study Group and the Children's Oncology Group to identify factors that divided patients into subsets with the most different rates of metastatic disease.
Of the nearly 1,700 patients included in the study, online August 12 in the Journal of Clinical Oncology, 269 (16%) had metastases, including 96 (5.7%) with lung metastases, 81 (4.8%) with bone involvement and 102 (6%) with bone marrow involvement.
Tumor invasiveness was the most significant predictor of lung involvement, although regional lymph node involvement contributed to the incidence of lung metastases.
Histology was the most important variable for bone and bone marrow involvement, followed by tumor invasiveness and regional lymph node involvement.
Among patients with lung involvement, 41% also had either bone or bone marrow involvement, but only 6% of patients without lung involvement had bone or bone marrow involvement.
Similarly, 59% of patients with bone involvement had concomitant bone marrow involvement, and 47% of patients with bone marrow involvement had concomitant bone involvement.
Using these results, the researchers constructed an initial staging algorithm that employed clinical and histologic characteristics. In this scheme, about a third of patients would not require bone scan or bone marrow evaluation.
"The Children's Oncology Group (a National Cancer Institute supported clinical trials group and the world's largest organization devoted exclusively to childhood and adolescent cancer research) is considering using this algorithm in future clinical research studies for children with rhabdomyosarcoma," Dr. Weiss said.
"Two-thirds of children with rhabdomyosarcoma have a less than 2% risk of metastatic disease, which could justify omitting specific staging evaluations," he added. "By providing probability data within our paper, physicians could choose to omit diagnostic studies in even more children, with a very small risk (less than 2%) of missing metastatic disease."
"Despite our successes, we realize the continued need to improve treatment for most children with rhabdomyosarcoma," Dr. Weiss said. "Ongoing collaborative research efforts within the Children's Oncology Group are focused on developing more effective therapies with fewer side effects."
J Clin Oncol 2013.
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