Overall survival comparison in patients with and without brain metastases treated with osimertinib for metastatic EGFR mutation positive non-small cell lung cancer (NSCLC).

Abstract

e21216 Background: With the development of Epidermal Growth factor receptor (EGFR) tyrosine kinase inhibitors such as Osimertinib, the landscape of lung cancer treatment and outcomes has changed. We aimed to describe the outcomes of patients treated with Osimertinib who have brain metastasis compared to those without brain metastases. Methods: This study involved patients diagnosed with metastatic non-small cell lung cancer (NSCLC) with EGFR mutation, from January 2010 to December 2018, who had treatment with Osimertinib at a dose of 80 mg daily. Retrospective data was collected through the electronic medical records from Sunnybrook Health Sciences Centre. Descriptive statistics were used to summarize the population characteristics. The log rank test was used to compare the survival distributions. Results: A total of 56 patients were included, the mean age at initial diagnosis was 63 years (range 27 – 85 years). Overall, 82.2% of this patient population received Osimertinib in 2nd line setting. A total of 50% (n = 28) had brain metastasis, and14.3% (n = 8) had leptomeningeal metastasis. Of the patients with brain metastasis, 14.3% (n = 4) had brain surgery. All patients with brain metastasis received central nervous system (CNS) radiation. With respect to radiotherapy modalities, 67.9% (n = 19) of patients with brain metastasis received gamma knife radiation, 42.85% (n = 12) were treated with stereotactic radiosurgery (SRS), and whole brain radiation was given to 57.1% (n = 16). Of those with brain metastasis, equal numbers of patients, 46.4% (n = 13), had EGFR mutations with exon 19-deletion and exon 21-L858R, 7.1% (n = 2) had unknown gene location EGFR mutation. The median OS for patients without brain metastasis was 38.6 months (95% confidence interval [CI] 37.5 – 39.8 months], compared to 35.9 months (95% [CI] 28.3 – 43.5 months] for those with brain metastasis ; log Rank (Mantel-Cox) p = 0.874. The median OS for patients diagnosed with leptomeningeal metastasis was 21 months (95% [CI] 2.9 – 39.0 months); log rank (mantel-cox). When brain metastasis was examined by EGFR mutation sub-groups, the median OS for patients with EGFR-exon 19-deletion was 26.4 months (95% CI [14.3 – 38.4 months], compared to 36.8 months, 95% CI [34.3 – 39.2 months] for those with EGFR-Exon 21-L858R; log Rank (Mantel-Cox) p = 0.49. Conclusions: Although there is an equivalent prevalence of brain metastasis between the two NSCLC EGFR mutation populations, in unadjusted analyses, no difference in OS was seen between patients with brain metastases compared to those without brain metastases. However, in the small number of patients with leptomeningeal disease, survival was shorter and a larger population should be studied to further explore this finding.