This multicenter phase III randomized trial protocol compares reduced-dose prophylactic radiation (40 Gy, 2-step40) versus standard-dose prophylactic radiation (56 Gy, SIB56) in patients with locally advanced squamous cell carcinoma of the head and neck. The trial is designed to test non-inferiority in time to treatment failure with the experimental arm, while evaluating whether reduced prophylactic dose decreases late toxicities.