Opportunities and Alternatives of Modern Radiation Oncology and Surgery for the Management of Resectable Brain Metastases

SIMPLE SUMMARY: Brain metastases are of increasing concern in the management of cancer patients. New systemic treatment options like specific targeting agents or immune checkpoint inhibitors allow for longer survival with a higher incidence of brain metastases over the course of the disease. Single or a few small, asymptomatic lesions are mainly treated with focal stereotactic radiotherapy. On the other hand, in many cases, large and, in particular, symptomatic metastases require microsurgical resection for immediate symptom relief. However, the indication for surgery can be challenging concerning the clinic, patient and tumor characteristics, and the availability of alternative conservative treatment options. Of note, with surgery alone, local recurrence rates are about 50%; therefore, additional RT is needed to improve outcomes. ABSTRACT: Postsurgical radiotherapy (RT) has been early proven to prevent local tumor recurrence, initially performed with whole brain RT (WBRT). Subsequent to disadvantageous cognitive sequalae for the patient and the broad distribution of modern linear accelerators, focal irradiation of the tumor has omitted WBRT in most cases. In many studies, the effectiveness of local RT of the resection cavity, either as single-fraction stereotactic radiosurgery (SRS) or hypo-fractionated stereotactic RT (hFSRT), has been demonstrated to be effective and safe. However, whereas prospective high-level incidence is still lacking on which dose and fractionation scheme is the best choice for the patient, further ablative techniques have come into play. Neoadjuvant SRS (N-SRS) prior to resection combines straightforward target delineation with an accelerated post-surgical phase, allowing an earlier start of systemic treatment or rehabilitation as indicated. In addition, low-energy intraoperative RT (IORT) on the surgical bed has been introduced as another alternative to external beam RT, offering sterilization of the cavity surface with steep dose gradients towards the healthy brain. This consensus paper summarizes current local treatment strategies for resectable brain metastases regarding available data and patient-centered decision-making.