关键词: 大体积脑转移瘤, 立体定向放射外科, 分期治疗, 剂量分割策略

Abstract: Objective To retrospectively investigate the efficacy and safety of different peripheral dose fractionation strategies in staged stereotactic radiosurgery (SRS) for the treatment of large brain metastases (LBM),and to explore histologically relevant strategy selection. Methods A retrospective study was conducted on 116 patients with 138 LBMs (diameter ≥3 cm or volume ≥10 cm³).All patients received two-stage staged SRS.MRI was performed approximately 25 days after the initial stage to plan for the second stage.Patients were divided into an escalation group (n=39),a maintenance group (n=41),and a de-escalation group (n=36) based on the peripheral dose changes between the two stages.Tumor volume changes,1-year local control rate (LCR),overall survival (OS),and adverse reactions were evaluated. Results The median LBM volume decreased from 17.65 cm³ in SRS1 to 9.95 cm³ in SRS2,and further to 5.85 cm³ at the last follow-up (all P＜0.001); the volume decreased significantly in all three groups (all P＜0.05).The overall 1-year LCR was 87.9%,with no statistically significant difference in 1-year LCR among the three groups (P=0.799).The median OS was 18.0 months,with no statistically significant difference in OS among the three groups (P=0.282).The incidence of AREs was 16.38%,with no statistically significant difference among the three groups (P=0.858).Subgroup analysis showed that the volume of LBM from lung cancer continued to decrease significantly after stage Ⅱ in the increasing and maintenance groups,while no further significant decrease was observed in the decreasing group; for LBM from breast cancer,only the increasing group continued to decrease significantly after stage II.In 41 patients,bevacizumab was added 3 days after the initial treatment,and no radiation necrosis or hemorrhage events were observed overall. Conclusion Two-stage SRS treatment for LBM can achieve good local control and safety.Given that the initial volume is larger in the escalation group,there are no significant differences in overall LCR,OS,and acute radiation effects (AREs) among the three dose fractionation strategies.However,histological subgroups suggest that the second-stage prescription should be optimized according to the individual:escalation or maintenance is more suitable for lung cancer LBM,while escalation is more suitable for breast cancer LBM.

Key words: Large brain metastases, Stereotactic radiosurgery, Staged treatment, Dose fractionation strategy