Prolongation of definitive head and neck cancer radiotherapy: Survival impact and predisposing factors.

Abstract Background and purpose To quantify the survival impact of prolongation of definitive radiotherapy (RT) for head and neck cancer in a national, modern cohort, and to identify predictive factors for prolongation. Materials and methods The National Cancer Database was queried for adults with non-metastatic cancer of the nasopharynx, oropharynx, larynx, or hypopharynx diagnosed 2004–2015, treated with definitive RT to 66–70 Gy in 30–35 fractions at 2–2.2 Gy per fraction. Multivariable Cox regression and propensity score matching were used to model the survival impact of RT prolongation, adjusting for potential confounders such as age and comorbidity. Predictors of RT prolongation were identified using multivariable multinomial logistic regression. Results In total, 36,367 patients were identified. As a continuous variable, RT prolongation increased the relative hazard of death by 2% per day (P  8 days) had lower absolute 4-year overall survival by 4% and 12%, respectively (P  11.5 patients/year). Conclusion RT prolongation, especially >8 days, is significantly deleterious. Systemic therapy and facility volume were major predictors. Early identification of patients at increased risk of treatment interruptions may facilitate implementation of preventive measures.