Abstract
Radiotherapy is a common treatment modality in the management of head and neck malignancies. In select clinical scenarios of well-lateralized tumors, radiotherapy can be delivered to the primary tumor or tumor bed and the ipsilateral nodal regions, while intentional irradiation of the contralateral neck is omitted. Proton beam therapy is an advanced radiotherapy modality that allows for the elimination of exit-dose through nontarget tissues such as the oral cavity. This dosimetric advantage is apt for unilateral treatments. By eliminating excess dose to midline and contralateral organs at risk and conforming dose around complex anatomy, proton beam therapy can reduce the risk of iatrogenic toxicities. Currently, there is no level I evidence comparing proton beam therapy to conventional photon radiation modalities for unilateral head and neck cancers. However, a growing body of retrospective and prospective evidence is now available describing the dosimetric and clinical advantages of proton beam therapy. Subsequently, the intent of this clinical review is to summarize the current evidence supporting the use of proton beam therapy in unilateral irradiation of head and neck cancers, including evaluation of disease site-specific evidence, unique challenging clinical scenarios, and ongoing clinical trials.
Highlights
Radiation therapy is a critical component in the multidisciplinary management of head and neck malignancies
We present the current level of evidence for Proton beam therapy (PBT) in unilateral irradiation and discuss ongoing clinical trials
Acute grade 2 to 3 toxicities were significantly improved with PBT, including reduced rates of mucositis (46% vs 91%), dysphagia (0% vs 27%), and weight loss (þ1.2% vs –5.3%)
Summary
Radiation therapy is a critical component in the multidisciplinary management of head and neck malignancies. The inherent physical properties of protons allow for rapid dose fall-off beyond the depth of the Bragg peak Based on these unique dosimetric capabilities, PBT is an ideal treatment modality for the irradiation of unilateral head and neck targets, providing conformal target coverage while effectively eliminating unnecessary exit dose to midline (eg, oral cavity) and contralateral normal tissues that do not require treatment for oncologic control (Figure). As many patients with indications for unilateral irradiation generally carry favorable prognoses, the reduction of chronic toxicities and prioritization of long-term quality of life outcomes after treatment is of growing importance [3]. To meet this need, PBT is a promising treatment modality in this patient population. We present the current level of evidence for PBT in unilateral irradiation and discuss ongoing clinical trials
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