Hypofractionated Stereotactic Radiosurgery (HF-SRS) in the Treatment of Brain Metastases
Single-fraction stereotactic radiosurgery (SF-SRS) is widely employed to safely and effectively treat small intracranial lesions. However, for large metastases or those in close proximity to critical structures, it can be difficult to obtain an acceptable balance of tumor control while avoiding damage to normal tissue when single-fraction SRS is utilized. Treating a lesion in two to five fractions of SRS (termed hypofractionated SRS, HF-SRS) potentially permits treatment of brain metastases with a total dose of radiation that yields both adequate tumor control and acceptable toxicity. Indeed, studies of HF-SRS in large brain metastases suggest that a superior balance of tumor control and toxicity is observed compared to single-fraction SRS. Nonetheless, a great deal of effort remains to understand mechanisms for HF-SRS driving the dose-volume-response relationship for tumors and normal tissues and to exploit this fundamental knowledge clinically. In particular, the application of HF-SRS in the setting of immunomodulating cancer therapies offers special challenges and opportunities.
