Heterogeneity in treatment regimens for AYA bone sarcomas: A comparison of outcomes at a single sarcoma center.

e23508 Background: Bone sarcomas account for about 5% of cancers in adolescents and young adults (AYA). Outcomes in this population are consistently inferior than children. It is poorly understood whether this is related to the tumor biology or the therapeutic approach. In addition, regimens used in AYAs are heterogeneous due to poor tolerance of pediatric regimens and lack of clinical trials specific to this population. We sought to study the therapeutic regimes and outcomes of AYA bone sarcoma patients (pts) to understand the optimal therapeutic approach better. Methods: From our institutional database, we extracted data of pts with the diagnosis of “osteosarcoma” (OS) and “Ewing sarcoma” (ES) in the AYA (15-39 yo) population from 2011-21. We included only pts with efficacy documented to different regimens. Descriptive statistics were used for patient demographics, presentation, regimens, and outcomes (Table). Objective response rate (ORR) was defined as the number of patients achieving a partial or complete response. Relapse rate (RR) was calculated for the pts that progressed after undergoing definitive curative intent treatment. Survival comparison between groups was made using the Kaplan Meier method and Log Rank Test. We used Fisher's exact test to compare differences in ORR between treatment groups. Results: We identified 30 ES and 44 OS pts. For both ES and OS, Kaplan Meier survival analysis showed no difference in presentation adjusted overall survival between treatment groups; ( x2 .351, p .55) for ES and ( x2 1.94 p .378) for OS. Importantly, in OS, ORR difference between Adria/IVCis and Adria/IACis was statistically significant ( p .0188). Conclusions: Our study shows the heterogeneity in first-line treatment strategies for AYA pts with bone sarcomas. For ES, response rates for VAC/IE and VAI were similar. In the OS cohort, we found ORR for Adria/IACis was 81% which was statistically different to pts receiving Adria/IVCis (ORR 30%). However, we saw relapses in 43% of pts treated with Adria/IACis. This indicates that the intra-arterial approach could be helpful for limb preservation but suggests the need for intense adjuvant chemotherapy to prevent relapses. There were no statistically significant differences in the survival outcomes of AYA bone sarcoma pts treated with pediatric versus adult regimens.[Table: see text]