CLRM-12 TITLE: STEREOTACTIC RADIOSURGERY (ADJUVANT OR NEOADJUVANT) COMPARED TO HIPPOCAMPAL AVOIDANCE WHOLE BRAIN RADIATION THERAPY WITH SIMULTANEOUS INTEGRATED BOOST FOR LIMITED BRAIN METASTASES (SRS-CHART): PHASE III OPEN-LABEL PARALLEL-GROUP RANDOMIZED CONTROLLED TRIAL

BACKGROUND: Surgery is indicated for large or symptomatic lesions in patients with limited brain metastasis (BM), followed by adjuvant stereotactic radiosurgery (A-SRS) to the cavity. Emerging evidence suggests promising role of neoadjuvant SRS (NA-SRS) before surgery with potentially lesser risk of leptomeningeal disease (LMD) and radionecrosis (RN). Hippocampal avoidance whole brain radiotherapy (HA-WBRT) results in better neurocognitive outcomes than standard WBRT, and use of simultaneous integrated boost (SIB) to surgical cavity can improve the local control. Absence of high-quality evidence forms the basis of current study comparing these three treatment strategies. OBJECTIVES: Primary endpoint is 1-year event-free survival (EFS) a composite endpoint comprising any local failure, LMD, DBF, symptomatic RN, or death as events. Other endpoints include individual endpoints and longitudinal neuro-cognitive function and quality-of-life assessment. METHODS: Target population includes adults with newly diagnosed BM (≤3 lesions) with life expectancy >1 year and one target lesion needing surgery. Patients will be randomized (1:1:1) to A-SRS (control arm) or one of two test arms (NA-SRS or HA-WBRT-SIB). In A-SRS arm, patients will receive single fraction (16-20Gy) or hypofractionated-SRS (24-27Gy/3 fractions or 30-32.5Gy/5 fractions) based on volume and location of cavity and other intact BM. In the test arms, patients will be allocated to either NA-SRS group (single/multi-fraction) followed by surgery within 2 weeks or HA-WBRT (30Gy/10 fractions) with SIB to cavity plus other intact BM (40-50Gy/10 fractions) combined with memantine within 6 weeks of surgery. A sample size of 168 patients is required to prove the superiority of test arms individually compared to the control arm with assumption of 1-year EFS of 43% versus 25% with a hazard ratio of 0.6 (two-sided alpha=0.05, power=80%, and 15% attrition rate). DISCUSSION: The study will generate level 1 evidence investigating the role of NA-SRS or HA-WBRT-SIB compared to A-SRS in limited brain metastases.