Stereotactic Radiosurgery (SRS) for Brain Metastasis in the Era of Evolving Systemic Treatment (Immunotherapy or Targeted Therapy) in Patients with Non-Small Cell Lung Cancer (NSCLC)

Abstract

With evolving role for targeted and immunomodulatory agents, the survival rate of NSCLC has been improved even with brain metastasis. This study analyzed the outcome of brain metastasis treated with SRS in conjunction with immunotherapy and target therapy as well as chemotherapy. After obtaining institutional review board (IRB) approval, 229 patients with NSCLC with brain metastasis treated with SRS at our institution were retrospectively reviewed from 2008-2021. Demographic information (e.g., age, sex, race), performance status (PS), extracranial metastasis (ECM), sequence of systemic therapy (SST) and surgery for BM (SBM) were reviewed and collected. Overall survival (OS) and intracranial recurrence free survival (ICRFS) were analyzed using the Kaplan-Meier method/Cox regression, and time to each event were measured from the date of the first SRS treatment. All statistical analyses were performed using SAS version 9.4 (Carey, NC). Of the 229 pts, the median age of pts at first SRS was 64.1 (range, 34.8- 83.0 years). 38.6% were biomarker (EGFR/ALK/ROS/PDL1) positive, and 30% were PDL1 positive. 28.8 % had surgery before SRS. The median number of SRS was 1 (range, 1 - 6), and 10 patients received salvage whole brain radiation therapy (WBRT) after SRS. With a median follow-up of 9.6 months (mo), median OS and ICRFS were 14.0 mo and 8.1 mo respectively. On univariate outcome analysis, PS, ECM, SBM and PDL1 were associated with OS while biomarker, SBM and SST were closely related to ICRFS. Pts with poor PS had worse median OS of 8.3 mo compared to 29.1 mo with good PS (p = 0.001). Median OS for no ECM vs. ECM were 20.7 mo vs. 9.6 mo respectively (p = 0.002). Patients who underwent SBM initially had better median OS of 28.7 mo compared to 9.9 mo without SBM (p<0.001). There was a trend of significant impact of positive PDL1 on median OS (21.1 mo vs. 11.7 mo, p = 0.06). Similarly, SBM was found closely related to ICRFS with median ICRFS of 8.1 mo vs. 4.9 mo for those with and without SBM respectively. Both positive biomarker (13.1 mo vs. 6.4 mo, P = 0.17) and SRS first SST (8.1 mo vs. 4.9 mo, p = 0.11) demonstrated a trend of increased median ICRFS. On multivariable analyses, no SBM was linked with worse OS (HR: 1.85; 95% CI:1.15 - 2.97; p = 0.01) and decreased ICRFS (HR: 1.65; 95% CI: 1.09 - 2.51; p = 0.02). Of 31 pts with information on cause of death, 3.2% died from brain metastasis related cause. This study demonstrated effective treatment of brain metastasis in NSCLC with multiple SRSs, especially for patients with favorable prognosis. Of noticed there was only a small number of patients received salvage WBRT and most patients didn't die from brain metastasis related progression.