This randomized phase II trial evaluated whether the combination of cisplatin and paclitaxel plus All-trans retinoic acid (ATRA) increases Response rate (RR) and Progression-free survival (PFS) in patients with advanced Non-small cell lung cancer (NSCLC) with an acceptable toxicity profile and its association with the expression of Retinoic acid receptor beta 2 (RAR-beta2) as a response biomarker.