(P 83) OUTCOMES OF MULTIMODAL PERIOPERATIVE TREATMENT IN OSTEOSARCOMAS OF THE JAW

Objective: Osteosarcoma of the jaw (mandible and maxilla) is a rare subset of osteosarcoma that has typically been associated with a higher propensity for local recurrence, but lower risk of metastasis as compared to conventional high-grade OS of the extremity. We previously reported improvement in local control (LC) with postop RT; however, there is limited data regarding the role of perioperative chemotherapy and outcomes.

Methods: Patients with jaw OS were retrospectively identified within an institutional pathology database from 9/2020 to 11/2024. Patients were included if they underwent treatment at MD Anderson Cancer Center, had surgical resection of the primary tumor, and had adequate follow up data available. Clinical and pathologic features were collected.

Results: As of submission, 83 patients with jaw osteosarcoma who underwent surgical resection were identified who met inclusion, with 81/84 (96.4%) presenting with localized disease. Initial treatment was resection alone (28/84,33.3 %), resection with radiation (14/84, 16.7%), or perioperative chemotherapy with resection +/- radiation (42/84, 50%). Patients diagnosed more recently and with positive margins (p=0.004) were more likely to receive RT. First line chemotherapy regimens were heterogeneous, with doxorubicin/cisplatin as the most common regimen (21/42), which demonstrated variable tumor necrosis (36-86%). The median time to local recurrence was 12.7 months, which occurred in 23/84 pts. Patients with localized disease who received any RT vs no RT had a reduced local relapse rate (18.2 vs 30.6%), while chemotherapy vs no chemotherapy did not significantly affect local relapse rate (p=0.32). Patients who received chemotherapy had no significant difference in time to local recurrence, but further comparative analysis of chemotherapy response in more cases is ongoing.

Conclusion: This expanded series confirms the utility of RT in improved LC in patients with jaw osteosarcoma. Although chemotherapy did not significantly change local control rate, further detailed analysis is pending.