ESTRO 2025 - Abstract Book

S722

Clinical - CNS

ESTRO 2025

significantly lower 5-year PFS than initial diagnosed meningioma (48.5 vs. 81.4%, p<0.001). FSRT and SRS groups showed no statiatically different PFS. In multivariate analysis, WHO grade 3 (hazard ratio [HR], 1.53; 95% CI, 1.60 13.36; p=0.004) and recurrent mass (HR 2.52, 95% CI 2.73-56.72, p=0.001) were identified adverse prognostic factor for PFS. Conclusion: Radiotherapy in patients with intermediate and high-risk meningiomas showed favorable PFS. WHO grade 3 and Recurrent mass were adverse prognostic factors for recurrence, the more aggressive strategy of radiotherapy such as dose escalation may need to be considered in these patients. References: Rogers, Leland, et al. "Intermediate-risk meningioma: initial outcomes from NRG Oncology RTOG 0539." Journal of neurosurgery 129.1 (2017): 35-47. Weber, Damien C., et al. "Adjuvant postoperative high-dose radiotherapy for atypical and malignant meningioma: a phase-II parallel non-randomized and observation study (EORTC 22042-26042)." Radiotherapy and oncology 128.2 (2018): 260-265. Rogers, C. Leland, et al. "High-risk meningioma: initial outcomes from NRG Oncology/RTOG 0539." International Journal of Radiation Oncology* Biology* Physics 106.4 (2020): 790-799 Digital Poster The infratentorial localization of brain metastases in non-small cell lung cancer indicates a poorer prognosis and distinct prognostic factors Zheqing Liu 1 , Zhengting Chen 2 , Fei Lu 2 , Simeng Tan 2 , Na Peng 2 , Chaozhen Shang 2 , Guoxu Wang 2 , Yaoxiong Xia 2 , Shaoxiong Wu 3 1 Department of Radiotherapy, Yunnan Cancer Hospital, Kunming City, Yunnan Province, China. 2 Department of Radiotherapy, Yunnan Cancer Hospital, Kunming, China. 3 Department of Radiation Oncology, Sun Yat-Sen University Cancer Center, Guangzhou, China Purpose/Objective: Despite the potentially life-threatening nature of infratentorial brain metastases (BM) due to the anatomical features and physiological functions of the posterior cranial fossa, its true prognosis compared with supratentorial BM remains unclear(1–4). We conducted a matching comparison of the prognosis between non-small cell lung cancer patients with and without infratentorial BM, and analyzed prognostic factors including the radiotherapy (RT) method. Material/Methods: From July 15, 2010 to June 2, 2023, a total of 392 patients who received RT for BM were eligible for inclusion, including 167 patients with infratentorial BM and 225 patients without infratentorial BM. 1:1 propensity score matching was used to select the patients with balanced prognostic characteristics. Using Kaplan-Meier method, Log rank test and Cox proportional hazard model to analyze the intracranial control and overall survival (OS). Results: 115 patients without infratentorial BM and 115 patients with infratentorial BM were matched into the study. There were no significant differences in extracranial progression-free survival (p=0.149), intracranial local progression-free survival rate at 2year (47.8% vs.60.4%, p=0.629) and intracranial distant progression-free survival rate at 2year (53.6% vs.72.2%, p=0.183) between the two groups respectively. However, the non-infratentorial BM group showed Keywords: Meningioma, recurrence, intermediate-high risk 3308