(P 120) SURVIVAL OUTCOMES AND ROLE OF CHEMOTHERAPY IN PATIENTS OLDER THAN 40 YEARS WITH OSTEOSARCOMA (OLD-SARC STUDY).

Objective: Osteosarcoma predominantly affects adolescents and young adults, but a second incidence peak occurs in individuals >40 years. Older adults often have higher comorbidity burdens, lower chemotherapy tolerance, and limited representation in clinical trials, leading to scarce evidence-based guidance.
This study aims to describe clinical characteristics, treatment patterns, and outcomes of patients aged ≥40 years with osteosarcoma and assess chemotherapy’s safety and efficacy.

Methods: We conducted a single-center retrospective study of patients aged ≥40 with histologically confirmed osteosarcoma treated at McGill University Health Centre (MUHC) from 2014–2024. Data were sourced from the CanSaRCC and SaRC-Q registries. Endpoints included overall survival (OS), progression-free survival (PFS), and objective response rate (ORR) per RECIST 1.1. OS was analyzed via Kaplan-Meier and log-rank tests.

Results: We included 40 patients (median age 64 [range 40–101]; 55% male) (Table 1). Most tumors were appendicular (57.5%) and high-grade conventional osteosarcoma was the most frequent subtype (50%). At diagnosis, 67.5% had localized and 32.5% had metastatic disease. Among localized cases, 37% received neoadjuvant and 33.3% adjuvant chemotherapy. Doxorubicin plus cisplatin was the most used regimen. Among 15 evaluable metastatic patients treated with first-line chemotherapy, ORR was 13.3% (2 partial responses); 20% achieved stable disease; 60% had progression. Median OS was not reached for localized disease. Recurrence occurred in 7 patients (17.5%) locally, 4 (10%) metastatically, and 1 (2.5%) with both. Median OS in metastatic disease was 6.97 months (95% CI: 3.49–10.44). The 5-year OS was 51.1% (localized) vs. 4.0% (metastatic). Mean PFS with first-line chemotherapy was 4.39 months (range 1.41–44.38). Median number of lines was 1.5 (range 0–4). Of 16 patients treated, 25% had treatment interruptions and 50% required dose reductions.

Conclusion: Older patients with localized osteosarcoma benefit from multimodal therapy, though outcomes are inferior to younger counterparts. In metastatic disease, prognosis remains poor, with modest chemotherapy benefit and frequent dose modifications. These findings highlight the need for better systemic therapies and greater inclusion of older adults in sarcoma trials.

Table 1. Demographics and clinical characteristics