(P 79) HEAD AND NECK OSTEOSARCOMA: THE EXPERIENCE OF 52 CASES FROM A SINGLE TERTIARY INSTITUTION OVER 25 YEARS

Objective: The present study aimed to estimate the survival outcomes of patients with head and neck osteosarcoma (HNOS) and investigate prognostic factors affecting treatment outcomes.

Methods: We reviewed 52 patients with pathologically confirmed HNOS (1996-2020), excluding radiotherapy (RT)-induced HNOS. All patients received curative surgery (S) with or without other treatment modalities (S alone, n=6, 11.5%; S+chemotherapy [CT], n=22, 42.3%; S+RT, n=3, 5.8%; and S+CT+RT, n=21, 40.4%). The median follow-up duration was 3.9 years.

Results: The mandible was the most common site of origin (n=32, 61.5%). Most patients had osteoblastic histology (n=28, 53.8%). The 2-year overall (OS) and disease-free survival (DFS) rates were 79.3% and 55.5%, respectively. Eighteen (34.6%) and three (5.8%) patients experienced local and regional recurrence with a 2-year locoregional relapse-free survival of 68.7%. Distant metastasis was identified in 17 patients (32.7%) with a 2-year distant metastasis-free survival of 67.5%. Lung (n=11, 21.2%) was the most commonly involved. On univariate analysis, age >40 years (p=0.034) and RT (p=0.037) were risk factors for poorer OS. Tumors >3.7 cm were associated with poorer DFS (p=0.041). Among 17 patients receiving adjuvant RT, unplanned prolongation of RT ≥5 days was associated with poorer OS (p=0.003) and DFS (p=0.013).

Conclusion: The benefit of combined modalities was not clear for surgically treated HNOS patients in the current study. The risk of local recurrence was comparable to that of distant metastasis, and the role of adjuvant RT warrants further investigation. It would be safe to limit any unplanned RT prolongation to less than 5 days.