Korean Ethnicity as Compared with White Ethnicity Is an Independent Favorable Prognostic Factor for Overall Survival in Non-small Cell Lung Cancer before and after the Oral Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitor Era

Background: We have previously demonstrated, using a regional California Cancer Registry database, that Asian ethnicity is an independent favorable prognostic factor for overall survival (OS) in non-small cell lung cancer (NSCLC). Methods: Retrospective population-based analysis of Korean and US white patients with NSCLC with known smoking status from Samsung Cancer Center, Seoul, South Korea, and a Southern California Regional Cancer Registry between 1998 and 2005 with follow-up through February 2008 to allow for even case ascertainment periods before and after 2002, when epidermal growth factor receptor tyrosine kinase inhibitors were introduced in Korea and considered as the year of reference. Results: A total of 4622 Korean and 8846 US white patients were analyzed. Median age of diagnosis was 63 years versus 71 years for Korean and white patients, respectively (P < 0.0001). A total of 34.5% of Korean compared with 8.2% white patients were never-smokers. There was significant OS improvement in never-smokers when compared with ever-smokers among either Korean patients (p < 0.0141) or US white (p < 0.0397), respectively. There was significant improvement in OS among Korean patients from 2002 to 2005 compared with 1998-2001 (p < 0.0001) but not among US white patients (p = 0.5641). Except for stage II patients (p = 0.0723), univariate analysis revealed Korean patients had improved OS compared with US white patients among stages I, III, and IV, respectively (all p < 0.0001). Multivariate analysis revealed Korean ethnicity (versus white; hazard ratio (HR) = 0.869; p < 0.0001) was an independent favorable factor for OS. The adjusted HR for OS Korean ethnicity when compared with white ethnicity improved during 2002-2005 (HR = 0.795; p < 0.0001) compared with 1998-2001 (HR = 0.889; p = 0.0013). Conclusions: These results suggest that Korean ethnicity compared with US white ethnicity is an independent favorable prognostic factor for OS in NSCLC. In addition, greater survival benefit among Korean patients with NSCLC was noted in the postepidermal growth factor receptor tyrosine kinase inhibitor era (2002 and after) compared with US white ethnicity.