Long-term impact of bevacizumab for the treatment of brain radiation necrosis

Purpose: To evaluate short and long-term efficacy of bevacizumab (Bev), for the treatment of radiation necrosis (RN) in patients with brain metastasis after stereotactic radiosurgery (SRS). Methods: The database of a tertiary medical center was reviewed for all adult patients treated by Bev (from January 2018 to January 2023) for RN after having received SRS for BM. Clinical and MRI data were systematically collected at baseline, immediately after the completion of Bev treatment, and at 6, 12, and, when available, 24 months post-treatment. Results: The cohort included 23 patients with a total of 31 RN lesions (defined as target lesion) which have been previously treated by SRS, either as single-session SRS (27/31) or as fractionated stereotactic radiotherapy (4/31). Median follow-up time was 15 months (range: 8-28.5). Immediately after completion of Bev, 15 patients (65.2%) exhibited a complete/partial response, 6 (26.1%) had stable disease, and 2 had progressive disease (8.7%). thirteen patients (56%) improved clinically. Greater than 50% reduction in volume was observed in 84% of target lesions. At 12 months, among the 13 patients still evaluable (9 other being deceased, 1 loss to follow up), three continued to improve, and four remained stable. Median volume of target lesion was then 1.4 cm³ (range 0.7–2.9) demonstrating a reduction of 67.4% compared to the initial target volume, which was 4.35 cm³ (range 2.14–10.37). During the entire follow-up period, 11 patients experienced regrowth of the target lesion; median time to progression was 7 months. Five underwent Bev re-challenge, but only 2 responded. Conclusion: Bev for the treatment of SRS-induced RN was associated with a high initial response rate, significant lesion reduction, and prolonged clinical improvement. However, the high rate of lesion regrowth (50%) and poor response to Bev re-challenge highlight the complexity of diagnosis and treatment of RN.