Bevacizumab Plus FSRT Versus Hippocampus-Avoidant WBRT in Lung Adenocarcinoma With Extensive Brain Metastases

Background Brain metastases represent a severe complication of lung adenocarcinoma, significantly impairing both survival and quality of life. For patients with multiple or large brain metastases who are not candidates for stereotactic radiosurgery (SRS), hippocampus-avoidant whole-brain radiotherapy is considered a standard treatment option. However, this approach is limited by residual neurocognitive decline and suboptimal intracranial disease control. Bevacizumab, an anti-vascular endothelial growth factor (VEGF) monoclonal antibody, has been shown to normalize tumor vasculature, enhance radiation sensitivity, reduce cerebral edema, and lower the risk of radiation-induced brain necrosis. Fractionated stereotactic radiotherapy (FSRT) offers effective local control with reduced toxicity compared to single-session SRS. A prior phase 2 study demonstrated promising efficacy and safety of FSRT combined with bevacizumab in this patient population. The present phase 3 trial aims to test the hypothesis that FSRT plus bevacizumab (FSRT-Bev) improves intracranial control and reduces neurocognitive toxicity compared to hippocampus-avoidant whole-brain radiotherapy with simultaneous integrated boost (HA-WBRT-SIB). Study Design This is a prospective, open-label, phase 3 randomized controlled trial being conducted at Sun Yat-sen University Cancer Center. Patients are randomized in a 1:1 ratio to one of two treatment arms: Arm A (Experimental): FSRT combined with bevacizumab; Arm B (Control): HA-WBRT with SIB Treatment Interventions Arm A: FSRT is delivered to the gross tumor volume (GTV) at a total dose of 30 Gy in 5 daily fractions (6 Gy per fraction) using image-guided radiotherapy (IGRT). Bevacizumab is administered intravenously at a dose of 7.5 mg/kg every 3 weeks for 4 cycles, beginning one week prior to the start of FSRT. Arm B: Hippocampus-avoidant whole-brain radiotherapy is delivered at a dose of 25 Gy in 10 daily fractions, with a simultaneous integrated boost (SIB) to gross metastatic lesions up to 40 Gy in 10 fractions. Co-Primary Endpoints 1. Intracranial Progression-Free Survival (IPFS): Defined as the time of randomization to the first intracranial progression or death. 2. Neurocognitive failure Rate at 6 Months Post-Radiotherapy: Assessed using the reliable change index (RCI) based on validated neurocognitive tests, including the Hopkins Verbal Learning Test-Revised (HVLT-R), Controlled Oral Word Association Test (COWA), and Trail Making Test Parts A and B (TMT-A, TMT-B).