Effect of adjuvant radiotherapy treatment center volume on overall survival

Objectives: to examine the impact of radiotherapy center volume on overall survival in patients with oral cavity and oropharyngeal squamous cell carcinoma getting adjuvant radiation therapy after receiving surgery at a high-volume center.

Materials and methods: a retrospective study was conducted on patients with oral cavity squamous cell carcinoma or oropharyngeal squamous cell carcinoma treated surgically at a tertiary institution from 2000 to 2012 who received adjuvant radiotherapy. The outcome variable was overall survival and the independent variable was location of adjuvant radiation therapy: high-volume center (HVC) versus low-volume center (LVC). Cox proportional hazards models were used to assess associations between predictors of death. Variables that were found to be significant at the α = 0.10 were included in a multivariable model.

Results: 336 patients met inclusion criteria. One-hundred thirty-nine patients received adjuvant radiation therapy at HVC and 197 patients received adjuvant radiation therapy at LVC. A univariate Cox proportional hazards model identified the variables location, age, marital status, subsite, T stage, extracapsular extension, and smoking status to include in a multivariable model. Age, subsite, T stage, and extracapsular extension were independent predictors of overall survival (p < .05). Location (p = .55), marital status (p = .29), and smoking status (p = .22) were not statistically significant predictors of survival.

Conclusion: After surgery at a HVC, the volume of adjuvant radiation therapy center was not significantly associated with overall survival. Significant predictors of survival included age, subsite, T stage, and extracapsular extension.