A narrative review of intensity-modulated proton therapy for head and neck cancer

Background and Objective: We aim to summarize and discuss the literature on intensity-modulated proton therapy (IMPT) in head and neck cancer and elucidate its benefits and limitations in a clinical setting. Head and neck cancer treatment involves a multi-disciplinary approach, with radiation therapy playing an integral role. Historically, photon therapy techniques, such as intensity-modulated radiation therapy (IMRT), have been utilized to manage head and neck cancer. In recent years, proton therapy has grown in popularity as a potential radiotherapy to provide favorable outcomes and limit toxicities in an aging patient population. The physical properties of protons provide a dosimetric advantage, where protons are deposited at a narrow range of tissue depth, termed the “Bragg peak”. Localization of the Bragg peak onto the desired target volume and the minimal to no exit dose of protons limit healthy tissue radiation. IMPT is the most recently developed delivery method of delivering protons, where it uses a pencil beam manipulated by magnets. In hopes to improve treatment outcomes and reduce toxicities, studies on IMPT have gained traction in its role in treating head and neck cancers. including oropharyngeal, nasopharyngeal, and sinonasal cancer. Methods: To adequately review the literature on IMPT in head and neck cancer, we conducted a PubMed search using the following search syntax: ((“intensity-modulated proton therapy” OR “IMPT” OR “pencil beam scanning” OR “scanning beam proton therapy”) AND “head and neck cancer”). No timeframe filters were selected. Articles reported on clinical trial results in English were included in the study. Key Content and Findings: In this narrative review, we discuss the distinction in the properties of protons and the differences in treatment planning and delivery compared to photon therapy. We explore the clinical outcomes and toxicities of IMPT in the treatment of oropharyngeal, nasopharyngeal, sinonasal, reirradiation, and unilateral head and neck cancer. Conclusions: We highlight the promising outcomes and limited toxicities in utilizing IMPT for head and neck cancer treatment. Ongoing clinical trials are essential for elucidating the acute and long-term benefits of this radiation modality.