Head and neck cancers usually start in squamous cells that line the moist mucosal surfaces of the inside of the head and neck (for example, inside the mouth, nose, and throat). Squamous cell cancers are often referred to as head and neck squamous cell carcinomas.

Radiation therapy is one of the main treatments for head and neck cancer. The radiation doses used to kill cancer cells can also damage normal cells and cause side effects. Side effects of radiation therapy are cumulative. This means that the more courses of treatment done over time, the higher the risk of side effects.