(P 152) EFFICACY OF PALLIATIVE CHEMOTHERAPY AND LOCAL TREATMENTS IN ADVANCED CHONDROSARCOMA: A SUBTYPE-SPECIFIC RETROSPECTIVE ANALYSIS

Objective: Chondrosarcoma (ChS) represents a heterogeneous group of malignant cartilaginous tumors characterized by variable clinical behavior and therapeutic response Among these, MChS is a rare and aggressive variant often presenting in younger patients, yet some retrospective studies suggest it may be more chemosensitive compared to other subtypes. This study aimed to assess subtype-specific responses to palliative chemotherapy (CHT), progression-free survival (PFS), overall survival (OS), and the impact of adjunct local interventions in advanced ChS.

Methods: The retrospective analysis included patients (pts) with a confirmed diagnosis of unresectable or metastatic ChS, treated in our sarcoma clinic between 1998 and 2025. Median overall survival (mOS) and median progression-free Survival (mPFS) were calculated using Kaplan-Meier analysis with prognostic factors assessed with a log-rank test.

Results: 51 pts received palliative CHT (median age: 48 years) including pts with dedifferentiated (DDChS; n=9, 17.6%), mesenchymal (MChS; n=16, 31.4%) and high-grade conventional (CChS, n=26, 51%). For pts receiving first-line CHT (n=50) mOS was 14.9 months (mo), while mPFS 5 mo. MChS pts had longer mPFS - 8.77 mo, and mOS-18.33 mo than those with DDChS (mPFS: 7.1 mo; mOS: 8.21 mo) and CChS (mPFS: 3.48 mo; mOS: 9.79 mo). Objective Response Rate (ORR) was 19.6% for the entire cohort, including 25% for MChS; 15.4% for CChS, and 22.2% for DDChS. 17 pts received 2nd-line CHT with mPFS5.39 mo and ORR of 23.5% for the entire cohort (MChS-37.5% ORR; CChS-16.7% ORR). Pts receiving local interventions (metastasectomy: n=15, 29.4%; palliative radiotherapy: n=13, 25.5%; both: n=6, 35.2%) exhibited a trend towards longer OS (p= 0.1): 18.3 mo with vs 12.7 mo.

Conclusion: These findings highlight the heterogeneity of chondrosarcoma subtypes and suggest that MChS may derive greater benefit from systemic therapy. Local interventions may improve survival and merit integration into multimodal treatment strategies. The role of local therapies in prolonging survival warrants further investigation.