The Judicious Use of Stereotactic Radiosurgery and Hypofractionated Stereotactic Radiotherapy in the Management of Large Brain Metastases

SIMPLE SUMMARY: Brain metastases are the most common cause of cancerous brain tumors in adults. Large brain metastases are an especially difficult clinical scenario as patients often have debilitating symptoms from these tumors, and large tumors are more difficult to control with traditional single treatment radiation regimens alone or after surgery. Hypofractionated stereotactic radiotherapy is a novel way to deliver the higher doses of radiation to control large tumors either after surgery (most common), alone (common), or potentially before surgery (uncommon). Herein, we describe how delivering high doses over three or five treatments may improve tumor control and decrease complication rates compared to more traditional single treatment regimens for brain metastases larger than 2 cm in maximum dimension. ABSTRACT: Brain metastases are the most common intracranial malignant tumor in adults and are a cause of significant morbidity and mortality for cancer patients. Large brain metastases, defined as tumors with a maximum dimension >2 cm, present a unique clinical challenge for the delivery of stereotactic radiosurgery (SRS) as patients often present with neurologic symptoms that require expeditious treatment that must also be balanced against the potential consequences of surgery and radiation therapy—namely, leptomeningeal disease (LMD) and radionecrosis (RN). Hypofractionated stereotactic radiotherapy (HSRT) and pre-operative SRS have emerged as novel treatment techniques to help improve local control rates and reduce rates of RN and LMD for this patient population commonly managed with post-operative SRS. Recent literature suggests that pre-operative SRS can potentially half the risk of LMD compared to post-operative SRS and that HSRT can improve risk of RN to less than 10% while improving local control when meeting the appropriate goals for biologically effective dose (BED) and dose-volume constraints. We recommend a 3- or 5-fraction regimen in lieu of SRS delivering 15 Gy or less for large metastases or resection cavities. We provide a table comparing the BED of commonly used SRS and HSRT regimens, and provide an algorithm to help guide the management of these challenging clinical scenarios.