Proton therapy for head and neck cancer: current applications and future directions
Radiation therapy is a standard treatment modality for head and neck cancer. However, delivery of radiation therapy to areas of disease in close proximity to critical normal structures, can potentially result in severe toxicity. While advances in conformal radiation techniques, like intensity-modulated radiation therapy (IMRT) have led to improvements in the therapeutic ratio, significant treatment-related morbidity still exists. Proton therapy is an emerging and promising treatment modality for head and neck cancers, because of the potential to improve organ sparing and/or safely escalate doses of radiation delivered. Localized radiation therapy to limited areas of the head and neck, such as for a lateralized salivary gland tumor, can be delivered with proton therapy using current techniques. Proton therapy to the bilateral neck, as required for locally-advanced disease, will require the development of intensity-modulated techniques, intensity-modulated proton therapy (IMPT), using pencil beam scanning. Determining the proper role of proton therapy for head and neck cancer should be done in the setting of clinical studies, with careful attention to quality assurance, and meaningful measures of disease control, toxicity and quality of life.