P3.13-10 Factors Associated with Long-Term Survival of Stage IV NSCLC Patients on First-Line EGFR-Targeting Therapy

Abstract

To determine factors associated with long term survival in Stage IV, non-small cell lung cancer (NSCLC) patients receiving EGFR-targeting agents (EGFR-TA) as systemic anti-cancer treatment in the first-line setting at a Canadian tertiary cancer centre. Retrospective analysis was conducted on patients diagnosed with Stage IV (AJCC 7th edition) NSCLC between 1999 and 2014, and receiving EGFR-TA as first-line treatment. Demographic, clinical, histopathological, treatment and outcome data was extracted from the large, population-based institutional Glans-Look Lung Cancer Database. Long-term survivors (LTS) were defined as those surviving ≥ 18 months post EGFR-TA initiation. Correlates of survival were investigated via univariate analysis, Kaplan-Meier analysis using the log-rank test, and multivariate Cox regression. We identified 117 eligible patients. Median age was 65 (IQR 54.5-74) years, 61% female, 91% adenocarcinoma, 60% never smoking history, and 80% were identified as EGFR-mutant (remainder were untested and accessed EGFR-TA before routine testing was performed). Most common ethnicity (by place of birth) was North American (47%), followed by Asian (37%). 21% survived ≥ 18 months post-EGFR-TA initiation, with a median overall survival (mOS) of 46 vs. 13 months in those surviving < 18 months post-EGFR-TA initiation (p <0.001). LTS were more likely to be over the age of 65 years at diagnosis (76% vs. 46%, p=0.012), receive palliative radiation therapy (72% vs. 27%, p<0.001), and possess Asian ethnicity (60% vs. 30%, p=0.044), although impact of age and radiation therapy did not retain prognostic significance in multivariate analysis after controlling for other measured confounders; Asian ethnicity was retained as a favorable prognostic factor for survival [HR: 0.5, 95%CI 0.3-0.8, p=0.005)]. Patients with Asian ethnicity revealed no significant demographic or clinical characteristics (notably gender, smoking status and EGFR mutation type) between LTS and non-LTS, with the exception of age. Asian LTS were significantly more likely to be ≥ 65 years of age at diagnosis (87% vs. 32%, p<0.001), a factor which retained significance as a favorable prognostic factor in multivariate analysis [HR: 0.3, 95% CI 0.2-0.7), p=0.004)]. Analysis of this population-based cohort identifies Asian ethnicity, and within this ethnic group, older age at diagnosis, as favorable prognostic factors for patients with Stage IV, NSCLC accessing EGFR-TA in the first-line setting. These findings help identify patients who derive the most benefit from EGFR-TA, and suggest that older, Asian patients represent a unique sub-population within metastatic NSCLC, who may possess different biological underpinnings of NSCLC, outside of a propensity to harbor EGFR mutations.