The Evolving Role of Particle Radiotherapy in the Treatment of Head and Neck Cancer

Radiotherapy has a proven role in the management of most types of head and neck cancer but results are suboptimal in certain clinical situations.  Particle radiotherapy offers the opportunity to improve outcomes in such cases.  Fast neutron radiotherapy is a high linear energy type of radiotherapy and may be advantageous for many “radioresistant” tumors such as salivary gland malignancies, mucosal melanomas, and sarcomas.  Proton radiotherapy offers greatly improved dose distributions compared to conventional photon radiation and this allows for higher radiation doses and potentially improved outcomes for tumors near critical structures such as the brain stem and optic structures and in the re-irradiation setting.  The applicability of proton radiotherapy in other settings is also discussed.  Heavier charged particles, such as carbon ions, offer both improved radiation dose distributions and the radiobiological advantage of fast neutron radiotherapy.  While data is limited, it appears that carbon ions are advantageous in the same subset of tumors as fast neutron radiotherapy, but the improved dose distribution theoretically should result in reduced morbidity.  Boron neutron capture therapy (BNCT) is a technique that has recently been used to treat recurrent head and neck tumors and new boron carrier compounds are being developed for this application.  Clinical data on the use of each of these modalities in the treatment of head and neck cancer is reviewed and their current role in the treatment of head and neck cancer is summarized