ABSTRACT
A hypofractionated approach has several theoretical advantages in comparison with single-fraction radiosurgery. Hypofractionating treatment promotes the transition of cells from radioresistant cell cycle phases to more sensitive phases. Additionally, resection cavities may be relatively hypoxic, reducing production of oxygen-based free radicals during irradiation that induce the DNA breaks that ultimately cause cell death. This premise, known as the oxygen enhancement ratio, was a fundamental supporting premise of preoperative stereotactic radiosurgery (SRS) trials reducing definitive dosing by 20% compared to those used for post-operative cases. Delivering high radiation doses per fraction in the proximity of various OARs requires accurate patient positioning to ensure treatment efficacy and safety. A frameless treatment technique using a thermoplastic immobilization mask that enables a reproducible setup in combination with image guidance will provide the high precision that is ideal for an HSRS approach.
