Comparison of Toxicity Associated With Early Morning Versus Late Afternoon Radiotherapy in Patients With Head-and-Neck Cancer: A Prospective Randomized Trial of the National Cancer Institute of Canada Clinical Trials Group (HN3)

PURPOSE: Based on our demonstration of a circadian rhythm in the human oral mucosa cell cycle, with most cells in the G(1) phase in the morning and M phase at night, we hypothesized that morning radiotherapy (RT) would lead to less oral mucositis than afternoon RT. METHODS AND MATERIALS: A total of 216 patients were randomized to morning (8-10 AM) vs. afternoon (4-6 PM) RT and stratified by radiation dose, smoking status, and center. Patients …