(P 79) AGE-BASED TREATMENT PATTERNS AND OUTCOMES OF LOCALIZED HIGH-GRADE OSTEOSARCOMA FROM A NATIONWIDE DATABASE: WHAT IS THE OPTIMAL STRATEGY FOR PATIENTS OLDER THAN 40 YEARS?

Objective: Standard treatment for osteosarcoma in pediatric and young adult patients typically includes surgery combined with neoadjuvant and adjuvant chemotherapy using methotrexate (MTX), doxorubicin, and cisplatin (CDDP). However, no consensus exists regarding optimal management in middle-aged and elderly patients. This study aimed to evaluate real-world treatment patterns and outcomes in patients aged >40 years using a nationwide registry in Japan.

Methods: Data were obtained from the Bone and Soft Tissue Tumor Registry by 89 JOA-certified hospitals. Patients with localized, high-grade osteosarcoma diagnosed between 2011 and 2020 were included. Clinical features, treatments, and outcomes were analyzed across three age groups: ≤40, 41–64, and ≥65 years.

Results: Among 886 patients, 622 (70%), 156 (18%), and 108 (12%) were aged ≤40, 41–64, and ≥65, respectively. Trunk tumors were more frequent in older patients (5% vs. 29% vs. 38%, p < 0.001). Definitive surgery was performed in 98%, 91%, and 85% (p < 0.001), and perioperative chemotherapy in 93%, 87%, and 41% (p < 0.001), respectively. Neoadjuvant chemotherapy was used in 96%, 80%, and 68% of chemotherapy cases. Use of MTX and CDDP declined with age: MTX (91%/41%/8%) and CDDP (94%/76%/42%) (≤40 / 41–64 / ≥65 years). Five-year DFS was 78.6%, 61.9%, and 48.0% (p < 0.001). Lack of definitive surgery was an independent poor prognostic factor for DSS in patients ≤65 years (p < 0.001). Among patients older than 40 years receiving perioperative chemotherapy, survival was similar between primary chemotherapy vs. upfront surgery groups.

Conclusion: This large-scale study shows that treatment patterns used in younger patients are also widely applied over age 40, while no consensus exists on optimal treatment for osteosarcoma in older patients. Given reduced histological response and increased toxicity in older patients, upfront surgery may be a non-inferior option. These findings prompt us to initiate preparations for prospective trials to define optimal strategies for the timing of surgery and chemotherapy in this age group through international collaboration.

Patient characteristics