Comparing Single vs Multiple Dose Radiation for Cancer Patients With Brain Metastasis and Receiving Immunotherapy

This study is an open-label, randomized, Phase III trial designed to ascertain whether fractionated stereotactic radiosurgery (FSRS) results in lower incidence of Grade 2 or higher adverse radiation effect (ARE) by 9 months compared to single fraction stereotactic radiosurgery (SSRS) in patients with large brain metastases who have received or will receive immune checkpoint inhibitor (ICI) targeted to the PD-1/PD-L1 axis within 30 days of stereotactic radiosurgery (SRS). Participants will be randomized 1:1 to either SSRS or FSRS, using a minimization randomization strategy considering 5 prognostic factors of interest: radiosurgery platform (gamma knife vs. LINAC), timing of immunotherapy relative to radiation (ICI within 30 days prior to Day 1 of SRS or not), surgical status (any resection cavity vs intact metastases only), predominant tumor type (Melanoma vs. all others), and prior courses of SRS for brain metastases (yes vs. no).