Radiation-associated versus sporadic osteosarcoma: A single-institution experience.

Abstract

11018 Background: Osteosarcoma (osarc) can be a rare complication from radiation (rt) therapy. Radiation-associated osarc (RAO) is reported to have a worse prognosis than non rt-associated osarc with limited objective data comparing the two. We conducted a retrospective study comparing demographics, therapy and outcomes of sporadic osarc (SO) to RAO. This study was confined to adults. Methods: We identified patients (pts) > age 18 years (yr) with osarc treated at our institution between 1990 and 2016 using an institutional database. We categorized tumors as SO or RAO based on history of prior rt within field of osarc. We extracted data on demographics, treatment, and primary malignancy characteristics. Results: We identified 159 pts with osarc, 28 were RAO tumors. Results are in Table 1. Median follow-up was 2.8 yr (0.1-19.6 yr). For RAO, median time from rt to diagnosis was 11.5 yr (1.5-28 yr) with a median cumulative dose of 60 Gy (44-75.8 Gy). Median progression free survival (PFS) and overall survival (OS) were not significantly different in pts presenting with metastatic osarc; PFS 10.3 mo vs 4.8 mo (p=0.45) and OS 15.6 mo vs 6.1 mo (p=0.96) in SO vs RAO pts, respectively. For pts with localized osarc, median relapse-free survival (RFS) and OS were significantly different, not reached vs 12.2 mo (p<0.001) and not reached vs 27.6 mo (p=0.001) in SO vs RAO, respectively. Conclusions: In our series, there was a significant difference in age, size and location of RAO vs non rt-associated osarc. Overall, all osarc pts with metastatic disease at diagnosis fared poorly. Pts presenting with localized RAO had worse outcomes than patients with localized SO. This was not associated with a detectable difference in therapy rendered or treatment effect in resection specimens. [Table: see text]