Patients with stage IIIB and IV NSCLC were included to receive Paclitaxel and Cisplatin (PC). Patients were randomized to receive ATRA 20 mg/m2/day (RA/PC) or placebo (P/PC) 1 week prior to treatment until completing two cycles. RAR-beta2 expression was analyzed by Immunohistochemistry (IHC) and RT-PCR in tumor and adjacent lung tissue.