(P 287) AN INTERNATIONAL SURVEY OF PROVIDER PRACTICES REGARDING BONE MARROW SAMPLING VERSUS [18F] FDG PET/CT IN THE DIAGNOSTIC EVALUATION OF BONE MARROW METASTASIS IN PEDIATRIC RHABDOMYOSARCOMA

Objective: Recently published recommendations indicate that RMS staging should include [18F] FDG PET/CT. The International Soft Tissue Sarcoma Consortium (INSTRuCT) Imaging & Pathology/Biology work groups initiated a “friendship” project to determine whether [18F] FDG PET/CT can be utilized as a non-invasive method for determining the presence of bone marrow metastasis and make bone marrow aspirates/biopsies unnecessary. We suspect that in some institutions, bone marrow aspirates/biopsies have already been replaced by the non-invasive [18F] FDG PET/CT. Therefore, we sought to define the current practices within the pediatric RMS community using a provider survey.

Methods: We created an anonymous online survey using REDCap. This survey was distributed to members of the pediatric oncology community worldwide. We used email and social media to distribute our survey. The survey consisted of 10 primary questions with the first five focusing on provider demographics and the last five on provider practices. The survey was open for three months from October 2023 – January 2024.

Results: In total, 165 participants attempted to complete the survey. 143 surveys were marked as complete and included in the analysis. The 143 respondents were from 26 different countries with the most responses coming from the United States, Germany, Italy, and Japan with 44, 28, 20 and 15 respondents, respectively. Most respondents (85%) identify as “senior physicians/attendings” and report that they practice in a large academic medical center (69%). Of the 143 respondents, 93% report that they perform bilateral bone marrow biopsies and aspirates (Bil BM/ASP) to evaluate for marrow disease (65% in all patients, 22% in high risk and intermediate risk groups, 14% in high-risk groups only). Of the 10% of respondents who do not perform marrows, providers indicate that they perform [18F] FDG PET/CTs instead, obtain bone marrow aspirates only or perform unilateral aspirate/marrow. Of the 143 respondents, 87% indicate that they perform [18F] FDG PET/CT at diagnosis (80% in all patients, 10% in high risk and intermediate risk groups, 10% in high-risk groups only). The 13% of respondents that do not perform [18F] FDG PET/CT indicate that “bilateral bone marrow aspirates/biopsies are the gold standard for the detection of metastatic disease in the bone marrow” (n = 2), “do not have access to a PET scanner” (n = 8), “PET/CT is too expensive” (n = 6), “the test is not covered by patient insurance” (n = 5), “I perform a bone scan instead” (n = 3) or chose “other” (n=6). Of the 124 respondents who stated that they perform [18F] FDG PET/CTs, 91% said that they also perform Bil BM/ASP. Lastly, when asked if they conclude that the patient has bone marrow metastases in the setting of tumor-free Bil BM/Asp but signs of bone marrow disease by [18F] FDG PET/CT, 29% said “yes”, 27% said “no” and 43% were “unsure”.

Conclusion: [18F] FDG PET/CT has striking potential in detecting bone marrow metastases and may identify sites of bone marrow disease that are not otherwise detectable. Most providers reported in our survey that they are performing bilateral bone marrow biopsies and [18F] FDG PET/CTs for rhabdomyosarcoma staging. This INSTRuCT friendship project will provide further insight into the sensitivity and specificity of [18F] FDG PET/CTs in the diagnosis of bone marrow metastases in patients with rhabdomyosarcomas and stimulate the discussion on how to address discordance when the FDG-PET/CT scan has increased uptake, but the bone marrow biopsy/aspirate is negative for disease.