Statistical analyses
Structural and biochemical recurrences were estimated using the competing risk methods. DFS and OS were estimated using the Kaplan–Meier method. The significance of predictors, such as biochemical control, structural control, and OS, were assessed in univariate and multivariate analyses using cox proportional hazard models. Statistical analyses using cox regression models were also performed to compare the rates of biochemical recurrence, structural recurrence, and OS between patients with tracheal involvement versus other forms of ETE. Dosimetry parameters were compared using unpaired t-tests. A two-sided p- value <0.05 was considered statistically significant for all measures