Figure 2.
Subgroup analysis demonstrating interactions between covariates and travel distance for treatment for those covariates for which significant interactions existed (race, primary site, and treatment modality). Each hazard ratio is the combined effect of the covariate and travel distance for treatment compared with a reference travel distance of <12.5 miles. Survival according to travel distance varied by (A) race (white, black, or other), (B) primary head and neck subsite (oral cavity, oropharynx, hypopharynx, or larynx); and (C) treatment modality (surgery, surgery and adjuvant therapy, radiotherapy, or chemoradiation).