Prospective evaluation of pre-treatment ctDNA burden in localized osteosarcoma to identify patients with inferior outcomes: A report from the LEOPARD study.

person David Stephen Shulman Dana-Farber/Boston Children's Cancer and Blood Disorders Center, Boston, MA info_outline David Stephen Shulman, Kelly S. Klega, Nan Chen, Elliot Gohn, Donovan Henry, Edwin Choy, Thomas Cash, Kris Ann Pinekenstein Schultz, Leo Mascarenhas, Rochelle Bagatell, Brian Turpin, Bhuvana Setty, Bradley DeNardo, Douglas S. Hawkins, Michael W. Bishop, Avanthi T Shah, Luke Devon Maese, Wendy B London, Steven G. DuBois, Brian D. Crompton

Authors person David Stephen Shulman Dana-Farber/Boston Children's Cancer and Blood Disorders Center, Boston, MA info_outline David Stephen Shulman, Kelly S. Klega, Nan Chen, Elliot Gohn, Donovan Henry, Edwin Choy, Thomas Cash, Kris Ann Pinekenstein Schultz, Leo Mascarenhas, Rochelle Bagatell, Brian Turpin, Bhuvana Setty, Bradley DeNardo, Douglas S. Hawkins, Michael W. Bishop, Avanthi T Shah, Luke Devon Maese, Wendy B London, Steven G. DuBois, Brian D. Crompton Organizations Dana-Farber/Boston Children's Cancer and Blood Disorders Center, Boston, MA, Massachusetts General Hospital, Boston, MA, Aflac Cancer Center/Children's Healthcare of Atlanta, Atlanta, GA, Children's Hospital & Clinics Minnesota, Minneapolis, MN, Cedars-Sinai Medical Center, Los Angeles, CA, Children's Hospital of Philadelphia, Philadelphia, PA, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, The Ohio State University/Nationwide Children's Hospital, Columbus, OH, Lifespan, Providence, RI, Seattle Children's Hospital, Seattle, WA, St. Jude Children's Research Hospital, Memphis, TN, UT Southwestern Medical Center, Dallas, TX, Hunstman Cancer Institute at the University of Utah, Salt Lake City, UT Abstract Disclosures Research Funding Conquer Cancer, the ASCO Foundation Alex's Lemonade Stand Foundation, Boston Children's Hospital, Dana-Farber Cancer Institute, Harvard Catalyst Program, Khimani Fund, National Cancer Institute/U.S. National Institutes of Health, QuadW Background: Prior retrospective analyses demonstrated that elevated pre-treatment ctDNA was associated with poor outcomes in newly diagnosed localized osteosarcoma. The primary objective of the LEOPARD study (Liquid biopsy in Ewing sarcoma and osteosarcoma as a prognostic and response diagnostic) was to determine whether patients with detectable pre-treatment ctDNA have an inferior event-free survival (EFS) compared to patients with undetectable ctDNA. Methods: The LEOPARD study is a prospective multicenter ctDNA study for patients with bone sarcomas. Patients enrolled through 12 primary study sites, or provided samples after enrolling on the Children’s Oncology Group Project EveryChild (ABTR18B1-Q). Eligible patients were 1-50 years of age at enrollment, had unresected, high-grade, localized, non-pelvic osteosarcoma and were to receive standard chemotherapy (primary centers only). We utilized a validated ctDNA assay, ultra-low pass whole genome sequencing (ULP-WGS), for ctDNA quantification based on tumor aneuploidy (limit of detection 3%). We compared EFS according to baseline ctDNA burden using two pre-specified cut points (detectable/undetectable [≥3%] and ~median [≥5%]. We planned 113 patients for 80% power to detect a difference in 2-year EFS of ~20% or greater for patients with detectable baseline ctDNA (2-year EFS: 68%) vs undetectable ctDNA (2-year EFS: 87%; one-sided log-rank test; ⍺=0.05). Results: From 10/1/17 to 3/3/23, 138 patients with osteosarcoma met eligibility and enrolled (67 - primary study centers; 71 - ABTR18B1-Q). 133 patients had an evaluable pre-treatment ctDNA measurement. Median age was 14.2 years (range: 4.2-30.3) and 50% of patients were male. At diagnosis, 63% had detectable ctDNA [median: 5.3% (range: 0-43.1)]. Age, sex, race, ethnicity, and tumor size were not associated with a difference in ctDNA burden. Baseline detectable ctDNA burden (≥3%) was associated with an increased risk of EFS-event (relapse/progression, second malignant neoplasm, death) compared to undetectable ctDNA (2-year EFS: 56% [95% CI 45-68%] vs. 88% [95% CI 78-98%]; P< 0.0001; Table). A similar pattern was seen using a cut point of ≥5% (53% [95% CI 41-67%] vs. 83% [95% CI 74-94%], P< 0.0001). Conclusions: These findings validate prior data associating baseline ctDNA detection with inferior EFS in patients with localized osteosarcoma and identify the first prospectively validated molecular biomarker in this disease. Baseline ctDNA burden is now positioned for implementation into upcoming therapeutic trials of risk-stratified therapy in localized osteosarcoma. N (%) 2-year EFS (95% CI) P-value Detectable ctDNA < 3% 49 (37) 88% (78-98%) < 0.0001 ≥ 3% 84 (63) 56% (45-68%) Median ctDNA < 5% 64 (48) 83% (74-94%) < 0.0001 ≥ 5% 69 (52) 53% (41-67%)