Missed radiation therapy sessions in first three weeks predict distant metastasis and less favorable outcomes in surgically treated patients with oral cavity squamous cell carcinoma

Background: We sought to investigate the prognostic impact of missed RT sessions in patients who had undergone surgery for oral cavity squamous cell carcinoma (OCSCC). Methods: The study sample consisted of 905 patients with surgically treated OCSCC who fulfilled criteria of RT course ≤8 weeks. The study participants were divided into three groups based on the characteristics of missed RT, as follows: 1) early missed RT, 2) late missed RT, and 3) RT as scheduled. Results: The 5-year overall survival (OS) rates in the early missed RT, late missed RT, and RT as scheduled groups were 53.0, 58.1, and 64.5%, respectively (p = 0.046). In multivariate analysis, early missed RT was independently associated with both OS (hazard ratio (HR) = 1.486; 95% confidence interval (CI): 1.122-1.966; p = 0.006) and the occurrence of distant metastasis (HR = 1.644; 95% CI: 1.047-2.583; p = 0.031). Conclusion: Early missed RT was independently associated with a higher occurrence of distant metastasis and less favorable OS in patients who had undergone surgery for OCSCC.