(P 59) CHONDROSARCOMA OF THE FLAT BONES: DIFFERENTIAL SURVIVAL BETWEEN HIGH GRADE LESIONS OF THE PELVIS AND SCAPULA

Objective: Studies have shown flat bone chondrosarcoma have worse outcomes than extremity tumors, but there is no data directly comparing different flat bone lesions. The primary aim of this study was to examine differences in recurrence and survival between pelvic and scapular chondrosarcoma.

Methods: Forty-two patients with scapular chondrosarcoma and 127 patients with pelvic chondrosarcoma who underwent surgical resection between 1989 and 2022 were retrospectively reviewed. Demographic and tumor characteristics were collected (Table 1) in addition to disease-specific survival (DSS) and recurrence-free survival (RFS). High grade tumors were defined as lesions that were grade 3 or 4 on surgical pathology.

Results: Patients with low-intermediate grade lesions of the scapula were more likely to have positive margins during definitive surgical management (14% vs 3%, OR 5, 95% CI [1.15,22.6], p=0.02), however this did not translate to differences in recurrence or survival (p>0.05). Among high grade tumors, patients with scapular lesions had worse RFS (HR 3.43, [1.21, 9.75], p=0.02) and DSS (HR 2.99, 95% CI [1.05, 8.51], p=0.04) (Figure 1). Five-year DSS for high grade pelvic and scapular tumors was 55% and 17%, respectively. There were no significant differences between the rate of positive margins or minimum tumor-free margin on final pathology for high grade lesions (p>0.10).

Conclusion: Five-year DSS survival for high grade chondrosarcoma of the flat bones is poor, particularly for those of the scapula. Despite a higher rate of positive margins for low-intermediate grade lesions of the scapula, there was no significant difference in survival compared to low-intermediate grades lesions of the pelvis.