2689 - Comparative Survival Analysis of Dose Fractionation Regimens in Fractionated Stereotactic Radiotherapy (FSRT) for Brain Metastases

Purpose/Objective(s):

This study aims to retrospectively analyze patients with brain metastases (BM) treated with fractionated stereotactic radiotherapy (FSRT) under two distinct dose-fractionation regimens: 5f×6Gy and 5f×7Gy. The hypothesis posits that variations in dose-fractionation regimens, along with other clinical factors, significantly influence survival and treatment outcomes in BM patients. The primary objectives are to compare survival and treatment outcomes between the two dose groups and to investigate the impact of key clinical factors on prognosis. The ultimate goal is to optimize radiotherapy regimens for BM, thereby improving patients' quality of life and extending survival.

Materials/Methods:

Clinical data from 352 BM patients who underwent FSRT between July 1, 2020, and June 30, 2024, were retrospectively collected. Patients were stratified into four subgroups based on bevacizumab (Bev) treatment status and FSRT dose-fractionation regimens (5f×6Gy vs. 5f×7Gy). The primary endpoint was intracranial progression-free survival (iPFS), and the secondary endpoint was overall survival (OS). Univariate and multivariate Cox regression analyses were employed to assess prognostic factors influencing iPFS and OS and to explore potential correlations among these factors. Propensity score matching (PSM) at a 1:1 ratio was applied to balance inter-group differences. Kaplan-Meier survival analysis was used to compare iPFS and OS across the subgroups.

Results:

Prognostic factors were analyzed and compared between each pair of subgroups. Key findings include:Within the same dose-fractionation regimen, patients receiving bevacizumab (Bev) exhibited significantly longer intracranial progression-free survival (iPFS) and overall survival (OS) compared to those without Bev; Among patients not receiving Bev, the 5f×7Gy group demonstrated significantly higher iPFS and OS than the 5f×6Gy group. However, in Bev-treated patients, the survival advantage of 5f×7Gy was less pronounced, with no significant difference between the two groups; The 5f×7Gy + Bev group showed significantly longer iPFS and OS compared to the 5f×6Gy + no Bev group.

Conclusion:

The 5f×7Gy dose-fractionation regimen, particularly when combined with bevacizumab, is associated with superior survival and treatment outcomes compared to the 5f×6Gy regimen. Key clinical factors, including the Karnofsky Performance Status (KPS) score, bevacizumab treatment, and FSRT dose-fractionation, were significantly associated with both iPFS and OS.These findings highlight the importance of incorporating the 5f×7Gy regimen with bevacizumab into clinical practice to optimize survival outcomes for BM patients. Furthermore, clinicians should consider factors such as KPS and Disease-Specific Graded Prognostic Assessment (DS-GPA) scores when evaluating patient prognosis. These results offer valuable insights for optimizing the allocation of treatment resources for BM.