The Prognostic Impact of Radiotherapy Delays in Oropharynx Carcinoma and the Role of p16 Status

Objective: A retrospective analysis was performed to evaluate the prognostic significance of treatment delays (TDs) for oropharynx carcinoma patients treated with definitive radiotherapy (RT), comparing p16⁺versus p16^-disease. Materials and Methods: Patients treated between 2012 and 2016 were analyzed (n=763). TD was defined as the time from pathologic diagnosis to initiation of RT. TD thresholds of ≤60, 61 to 90, and >90 days were used to stratify outcomes. Time on treatment (TOT) delays were estimated based on the RT fractionation. TOT delay of 1 to 3 days was compared with >3 days. Predictors of cancer-specific survival (CSS) and locoregional recurrence (LRR) were evaluated on multivariable analysis. Results: Six hundred fifty (85%) patients had p16⁺disease. On multivariable analysis, TOT delay of 1 to 3 days versus <1 day was associated with inferior CSS (hazard ratio [HR]=1.81; 95% confidence interval [CI]: 1.02-3.22). TD >90 versus ≤60 days (HR=1.68; 95% CI: 0.98-3.04) and 61 to 90 versus ≤60 days (HR=0.94; 95% CI: 0.60-1.48) was not associated with CSS. TD >90 versus ≤60 days (HR=1.29; 95% CI: 0.66-2.52), TD 61 to 90 versus ≤60 days (HR=0.98; 95% CI: 0.64-1.52), TOT 1 to 3 versus <1 day (HR=0.91; 95% CI: 0.39-2.11), and TOT >3 versus <1 day (HR=1.79; 95% CI: 0.80-3.99) were not associated with LRR. There was no interaction between p16 status and TD in relation to LRR (P=0.27) or CSS (P=0.17). Conclusions: TDs were not significantly associated with CSS or LRR. TOT of 1 to 3 days was associated with inferior CSS. p16 status should not be a significant factor when triaging RT start dates.