Background: We previously showed that Asian ethnicity was an independent favorable prognostic factor in non-small cell lung cancer (NSCLC). Many Asian NSCLC patients were never-smokers, and never-smokers had improved survival than ever-smokers. We investigated whether Asian ethnicity is a favorable prognostic factor independent of smoking status.
Methods: Retrospective population-based study of NSCLC cases from the cancer surveillance programs of three Southern California counties from 1991 to 2005.
Results: A total of 20,140 NSCLC patients with known smoking status were analyzed of which 9.1% were never-smokers and 6.5% were Asians. There was a threefold increase in the percentage of Asian never-smokers as compared with ever-smokers. Asians had the highest overall survival (OS) among the 4 major ethnicities (p < 0.0001) and never-smokers had improved OS over ever-smokers (p = 0.0183) by univariate analyses. By multivariate analyses, Asian ethnicity was an independent and favorable prognostic factor for OS (versus non-Asian; hazard ratio [HR] = 0.861, 95% confidence interval [CI]: 0.808-0.918, p < 0.0001), among smokers (versus non-Asian; HR = 0.867, 95% CI: 0.807-0.931, p < 0.0001), and among never-smokers (versus non-Asian; HR = 0.841, 95% CI: 0.728-0.971, p = 0.0180). Never-smoker was a favorable prognostic factor if ethnicity was not accounted for (versus ever-smoker; HR = 0.936, 95% CI: 0.886-0.988, p = 0.0169) but was no longer an independent favorable prognostic factor (versus ever-smoker; HR = 0.953, 95% CI: 0.902-1.007, p = 0.0861) after accounting for ethnicity.
Conclusions: Asian ethnicity is an independent favorable prognostic factor for OS in NSCLC regardless of smoking status.