P2.05-013 Stereotactic Brain Radiosurgery in Lung Cancer Patients in the Era of Personalized Therapy: A Review of Outcomes and Prognostic Scores Evaluation: Topic: Clinical Outcome

Abstract

Stereotactic brain radiosurgery (SRS) was demonstrated to provide good local control in patients with oligo-brain metastases (commonly defined as 4 or less). The discovery of different targeted therapies provided significant improvement in survival in the past decade. We reviewed the effectiveness of SRS in lung cancer patients with oligo-brain metastases and identified prognostic factors which potentially can aid better patient selection. Medical records of patients with brain metastases treated with SRS in Prince of Wales Hospital, Hong Kong in Jan 2010-July 2015 were reviewed. Outcomes including local control rate (LCR), distant brain control rate (BCR) and overall survival (OS) were analyzed. Prognostic factors were identified with univariate and multivariate analyses. Correlation with available prognostic scorings including RTOG Recursive Partitioning Analysis, Basic Score for Brain Metastases, the Score Index for Radiosurgery and Graded Prognostic Assessment was evaluated. Forty-eight patients with 66 lesions were treated with LINAC-based SRS with single dose of 12-24Gy (mean dose 18.1Gy). The distribution of different subtypes is as follows: Non-small cell lung cancer (NSCLC)/adenocarcinoma NOS n=18 (37.5%), EGFR mutation n=17 (35.4%), ALK IHC+ n=3 (6.3%), adenocarcinoma of unknown subtype n=2 (4.2%), squamous cell carcinoma n=5 (10.4%), small cell carcinoma n=2 (4.2%) and unknown subtype n=1 (1.8%). The median follow up time was 11.0 months (0.4-71.4 months). Five patients (9.4%) were symptomatic with acute brain edema. Seven patients (14.6%) had delayed seizure after a mean time of 10.1month (2.0-33.5 months). Six patients (12.5%) became steroid dependent. The median OS was 13.0 months. One year actuarial LCR was 73% and distant BCR was 67%. OS correlated significantly with all four scoring systems. Among NSCLC patients, those with activating EGFR mutation (exon 19 deletion or exon 21 L858R mutation) (n=12) had superior OS compared with non-mutational group (p=0.036, HR 2.811 95% CI 1.072-7.369), but there was no statistically significant difference on local or distant brain control. Concomitant whole brain radiotherapy (WBRT) did not significantly affect OS, local and brain control in the whole group and in EGFR activating mutant subgroup. SRS provided good control in patients with primary lung cancer with oligo-brain metastases. Current available prognostic scores provide good estimation of survival. Patients with EGFR activating mutation had superior survival after SRS compared with non-mutational NSCLC group.