P17.04.A INCREASED SURVIVAL IN THE STEREOTACTIC RADIOTHERAPY ERA COMPARED TO THE WHOLE BRAIN RADIOTHERAPY ERA IN PATIENTS WITH MULTIPLE BRAIN METASTASES

Abstract BACKGROUND Whole brain radiotherapy (WBRT) is increasingly being replaced by stereotactic radiotherapy (SRT) in patients with more than 3 brain metastases (BMs). Elective irradiation of healthy brain tissue is reduced by SRT and it is uncertain if this has a negative impact on survival rates. At the same time, several new systemic treatment options have become available (immunotherapy and targeted agents) to treat smaller BMs. Our study examines the time trends in survival rates of patients treated with radiotherapy for brain metastases during this era of shifting treatment paradigms. MATERIAL AND METHODS Patients with new BMs treated with SRT or WBRT between 2010 and 2023 were included. Patients were excluded if they had previously undergone radiotherapy of the brain. Survival time was calculated with BM diagnosis as starting point. Differences in survival between treatment years were evaluated using Log-rank tests. A P value of <0.05 (two-sided) was considered statistically significant. RESULTS 1106 patients were included for analysis. 832 (75%) were treated with SRT, while 274 (25%) were treated with WBRT. The median number of BMs was 2 (IQR 1-5), while 367 (33%) patients had more than 3 BMs. The proportion of patients with more than 3 BMs who were treated with SRT instead of WBRT increased over time: 2010-2014: 9 (11%); 2015-2019: 52 (31%); 2020-2023: 80 (68%). In the whole cohort, patients who underwent RT between 2020-2023 had significantly better survival (median 11 months) compared to those treated between 2010-2014 (median 8 months) and 2015-2019 (median 8 months) (P < 0.001). The same remained true for the subset of patients with more than 3 BMs (median survival 2010-2014: 5 months; 2015-2019: 6 months; 2020-2023: 7 months; P = 0.023). CONCLUSION In patients treated with radiotherapy for multiple (>3) BMs, survival increased significantly from the WBRT era (2010-2014) compared to the SRT and immunotherapy/targeted agents era (2020-2023).