Abstract B052: "Site-Specific Risk and Metastatic Patterns in Pediatric Osteosarcoma: A Retrospective Cohort Study from Puerto Rico"

Abstract Osteosarcoma (OS) is the most common primary bone malignancy in children and adolescents, with a peak incidence among the age range of 10–19. While representing only 2–3% of pediatric cancers, OS possesses a disproportionately high risk of early metastasis—most commonly to the lungs and lower extremities—contributing significantly to morbidity. Emerging data suggests that Hispanic populations, including Puerto Ricans, are more likely to present with metastatic disease, compounding their already increased cancer burden. Despite a high rate of medical insurance coverage across the island, geographic and socioeconomic disparities persist, particularly in rural municipalities, leading to delays in diagnosis and treatment. The anatomical site of the primary tumor may also influence both the likelihood of early detection and the biological aggressiveness of the disease. To explore this, we conducted a retrospective cohort study of pediatric OS patients (<21 years) between 2012-2024 at the University Pediatric Hospital (HOPU), Puerto Rico’s only supra-tertiary public pediatric oncology center. Patient data extracted from the Meditech NPR database included tumor location, stage at diagnosis, age, sex, and recurrence history. Among the 44 patients analyzed, tumors most frequently occurred in both right and left lower limbs, specifically 31.2% in the distal femur (n=14) and 22.1% in the proximal/distal tibia (n=10). Patient analysis revealed all metastatic cases (n=13) from the cohort involved long bones or the humerus. Specifically, lung metastases were confirmed in patients with tumors in the left and right distal femur, left tibia, left distal tibia, and left humerus. A metastatic case involving the right humerus harbored a TP53 mutation, suggesting aggressive tumor biology. One rare case involving tumor location in the left distal femur and mandible exhibited soft tissue metastasis. No vertebral cases documented distant metastases in the sample, although they remain high-risk due to anatomical proximity to the CNS. Our findings underscore a tendency for OS in long bones to metastasize to the lungs, while also identifying anatomical locations warranting heightened clinical suspicion. This is the first study to explore the association between tumor site and metastasis in Puerto Rican pediatric OS patients, offering insight into how clinical, biological, and regional factors converge to shape cancer outcomes in this vulnerable population. Citation Format: MiaSara Pérez Salvá, Gabriela S Pardo Toro, Carolyn Ruíz- Pérez, Rocío K. Rivera-Valentín. "Site-Specific Risk and Metastatic Patterns in Pediatric Osteosarcoma: A Retrospective Cohort Study from Puerto Rico" [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Discovery and Innovation in Pediatric Cancer— From Biology to Breakthrough Therapies; 2025 Sep 25-28; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2025;85(18_Suppl_2):Abstract nr B052.