PURPOSE: This subgroup analysis of a phase II trial was conducted to assess possible ethnicity-based trends in efficacy and safety in East Asian (EA) and non-EA populations with nonsquamous non-small cell lung cancer (NSCLC). MATERIALS AND METHODS: Never-smoker patients (n=240) with locally advanced or metastatic nonsquamous NSCLC included 133 EA patients randomized to pemetrexed supplemented with dexamethasone, folic acid, and vitamin B12 plus erlotinib (pemetrexed-erlotinib) (n=41), erlotinib (n=49), or pemetrexed (n=43), and 107 non-EA patients randomized to pemetrexed-erlotinib (n=37), erlotinib (n=33), or pemetrexed (n=37). The primary endpoint, progression-free survival (PFS), was analyzed using a multivariate Cox model. RESULTS: Consistent with the results of the overall study, a statistically significant difference in PFS among the three arms was noted in the EA population favoring pemetrexed-erlotinib (overall p=0.003) as compared with either single-agent arm (hazard ratio [HR], 0.48; 95% confidence interval [CI], 0.29 to 0.79; p=0.004 vs. erlotinib; HR, 0.40; 95% CI, 0.23 to 0.70; p=0.001 vs. pemetrexed). The EA patients treated with pemetrexed-erlotinib achieved a longer median PFS (7.4 months) compared with erlotinib (4.5 months) and pemetrexed (4.0 months). The PFS results also numerically favored pemetrexed-erlotinib in the non-EA population (overall p=0.210) (HR, 0.62; 95% CI, 0.37 to 1.05; p=0.078 vs. erlotinib; HR, 0.75; 95% CI, 0.42 to 1.32; p=0.320 vs. pemetrexed) (median PFS: pemetrexed-erlotinib, 6.7 months; erlotinib, 3.0 months; pemetrexed, 4.4 months). CONCLUSION: The PFS results from this subset analysis in both EA and non-EA populations are consistent with the results in the overall population. The PFS advantage for pemetrexed-erlotinib is significant compared with the single agents in EA patients.