BACKGROUND: The increasing incidence of radiation-induced osteosarcoma of the 
maxilla and mandible (RIOSM) has become a significant problem that can limit 
long-term survival. The purpose of this study was to analyze the association of 
clinicopathologic characteristics with treatment outcomes and prognostic factors 
of patients who developed RIOSM after undergoing radiotherapy for nasopharyngeal 
carcinoma (NPC).
METHODS: We reviewed the medical records of 53,760 NPC patients admitted to Sun 
Yat-sen University Cancer Center during the period August 1964 to August 2012. 
Of these patients, 47 who developed RISOM and met inclusion criteria were 
included in this study. Two of these 47 patients refused treatment and were then 
excluded.
RESULTS: For all patients treated for NPC at Sun Yat-sen University Cancer 
Center during the study period, the total incidence of RIOSM after radiotherapy 
was 0.084% (47/53,760). Two patients (4.4%) had metastases at the diagnosis of 
RIOSM. Thirty-nine of the 45 (86.7%) patients underwent surgery for RIOSM; most 
patients (24/39; 61.5%) who underwent resection had gross clear margins, with 15 
patients (38.5%) having either a gross or microscopic positive margin. All 
patients died. The 1-, 2-, and 3-year overall survival (OS) rates for the entire 
cohort of 45 patients were 53.3%, 35.6% and 13.5%, respectively. The independent 
prognostic factors associated with high OS rate were tumor size and treatment 
type.
CONCLUSIONS: RISOM after radiotherapy for NPC is aggressive and often eludes 
early detection and timely intervention. Surgery combined with postoperative 
chemotherapy might be an effective treatment to improve patient survival.