BACKGROUND Platinum-based chemotherapy (CT) is the standard treatment for advanced non-small-cell lung cancer (NSCLC). Unfortunately, the survival and response rate (RR) to CT is poor. There is great interest in new treatment strategies. One of this new strategies include the use of retinoids such as atRA. The synergistic effect of cytotoxic agents with retinoids has been demonstrated in lung cancer. At the INCan, our work group carried out a phase II study trial that included 107 patients with advanced NSCLC. They were randomized to receive atRA (20-mg/m2) or placebo combined with 80 mg/m2 of cisplatin and 175 mg/m2 of paclitaxel. The results showed a significant increase in the RR of the atRA group, reaching 55.8% ( 95% CI; 46.6-64.9%) compared with 25.4% (95% CI, 21.3-29.5%; p = 0.001) in patients who received placebo. Median Progression-free survival (PFS) in the atRA group was 8.9 months, while for those of placebo, PFS was 6.0 months (p = 0.008). There were no significant differences in the grade 3-4 side effects between groups, except for hypertriglycemia, which presented with greater frequency in the atRA group (p = 0.05). Immunohistochemical stains determine the RAR B2 expression in 6 of 60 tumor samples analyzed; however, all samples expressed RAR B2 in adjacent normal tissue.