Duration of radiation therapy is associated with worse survival in head and neck cancer

Introduction: Delays in radiation are multifactorial, frequent, and associated with poor outcomes. This study investigates the effect of both primary and adjuvant radiation therapy duration and their interaction with other measures of treatment delay on survival in head and neck squamous cell carcinoma (HNSCC). Methods: We built a retrospective cohort using the National Cancer Database, consisting of primary oral cavity, hypopharynx, larynx and oropharynx squamous cell carcinoma without distant metastasis and with at least six weeks of radiation. The primary exposure was the duration of radiation therapy (DRT), and the primary outcome was death. We estimated the association between DRT and 5-year overall survival (OS) using Kaplan-Meier curves and hazard ratios (HRs) with Cox proportional hazard regression. Results: In both primary (definitive) and adjuvant (post-surgical) radiation settings, increased DRT results in decreased survival. In the primary radiation cohort, 5-year OS was 59.7% [59.1%-60.3%] among those with 47-53 days DRT, which decreased significantly with each subsequent week to completion (81+ days: 38.4% [36.2%-40.7%]). In the surgical cohort, survival decreased 16.5% when DRT extended beyond 75 days (40-46 days: 68.2% [67.3%-69.1%] vs. 75+ days: 53.3% [50.1%-56.7%]). Multivariate analyses showed increased hazard of death with increased DRT (primary radiation: 81+ days HR: 1.69 [1.58-1.81]); surgical: 75+ days HR: 1.61 [1.37-1.88]), with effects intensifying when restricting to those receiving full-dose radiation. Conclusion: A prolonged DRT was associated with worse OS in head and neck cancer. Radiation treatment delays of even a week lead to a significant survival disadvantage. DRT had a stronger association with survival than time to initiation of postoperative adjuvant radiotherapy.