This is a comparative effectiveness review of alternative radiation therapy (RT) modalities in the treatment of head and neck cancer including: conventional or two-dimensional (2DRT), three-dimensional conformal (3DCRT), intensity-modulated (IMRT), and proton beam radiotherapy. Key questions that will be addressed are whether any of these modalities is more effective than the others: (1) in reducing normal tissue toxicity and adverse events, and improving quality of life; (2) in improving local tumor control, time to disease progression, and survival; (3) when used in certain anatomic locations or patient subpopulations; and, finally, (4) whether there is more variation in patient outcomes with any modality secondary to user experience, treatment planning, or target volumes.