Further stratification analyses in early stage NSCLC patients indicated that ERCC1 rs11615 AA genotype predicted a significant poorer OS than GG+GA genotypes in patients with squamous cell carcinoma (log-rank p = 0.004), those ever smoked (log-rank p = 0.018), those with ECOG performance status of 1 (log-rank p = 0.007), or those never receiving radiation therapy (log-rank p<0.001) (Fig. 4). Here, ERCC1 is linked to squamous cell carcinoma.