(P 345) SARCOMA BIOPSY COMPARISON BETWEEN REFERRAL CENTERS AND TREATING CENTERS: THE MUSCULOSKELETAL TUMOR REGISTRY (MSTR) EXPERIENCE

Objective: Inappropriate pre-referral biopsy presents potential risks and complications. The Musculoskeletal Tumor Registry (MsTR) is a centralized record of patient, tumor, treatment, and outcomes data on musculoskeletal malignancies. This is the first report of patient data from the MsTR and aims to examine biopsy patterns for bone and soft tissue sarcoma, specifically how biopsies are performed at referring versus treating centers and the proportion of attempted excisions prior to referral.

Methods: This analysis includes all MsTR patients diagnosed with bone or soft tissue sarcoma and a completed “Disease and Treatment Summary” form including a known biopsy date. Study variables included demographic information, tumor characteristics, and biopsy details. Frequency distributions and bivariate analyses examined associations between patient, tumor, or biopsy characteristics and institution type. Separate analyses limited to excisional biopsies were performed. Pearson’s chi-square test, Fisher’s exact test, or independent two-sample t-tests assessed statistical significance at p ≤0.05.

Results: Between 2016-2025, 889 patients at 7 centers were included, with 273 (30.7%) performed at the referring center. Of the biopsies performed at the referring center, 54.2% were incisional or excisional biopsies. Of 645 soft tissue sarcomas, 136 (21.1%) had incisional or excisional biopsy prior to referral. 85/94 (90.4%) of the excisional biopsies done prior to referral had positive margins or margins that were not possible to assess. Core needle biopsy was more commonly performed at treating centers (74.0% vs 44.7%, p< 0.001), whereas excisional biopsy was more commonly performed at referral centers (35.5% vs 9.6%, p< 0.001).

Conclusion: Inappropriate sarcoma excisions are known to impact patient care, resulting in diagnostic delays, increased need for additional interventions, and increased concern for local recurrence. Using the MsTR to compile comprehensive multi-institutional data and benchmarking, we found an overall rate of incisional biopsies or attempted excisions prior to referral to a sarcoma specialist of 4.9% in bone tumors and 21.1% in soft tissue tumors.