18063 Previous studies have shown pre and post-operative serum CEA levels are a prognostic factor in patients with lung cancer (LC). We prospectively investigated the clinical and pathological characteristics, as well as, prognostic significance of patients with IIIB and IV stage LC and the CEA serum elevation. From March of 2005 to January of 2007, 307 patients with IIIB and IV stage were included; several chemotherapy protocols including gemcitabine, vinorelbine or paclitaxel combined with cisplatin, carboplatin, or erlotinib were used. Serum CEA levels were obtained before and after 2 cycles of treatment. Stage was determined by CT and bone scans; 120 patients had brain CT scan at diagnosis due to neurological symptoms. 28.6% of the patients were stage IIIB and 61.4% stage IV and 18% of patients had CNS metastasis at diagnosis. Histology was adenocarcinoma in 69.1% and epidermoid in 30.9%. Mean CEA was 11.3 ng/ml ± 24.5 with median of 6.7 (range 0.2 to 4,578). Patients with CEA levels > 10, 20, 50 and 100 were 43.6, 32.5, 24 and 17.9%; respectively. Associated factors with CEA >20 were age >62 (p=0.02), stage (p=0.05), CNS metastasis (p=0.0001) and histology (p=0.01). However, in the logistic regression analysis the only associated factors were histology (p=0.0001) and CNS metastasis (p=0.0001). Patients with CEA elevation >20 had a hazard ratio of 26.3 (CI 11.2 to 61.6) for the development of brain metastases. Overall survival associated factors were poor status performance (p=0.006), tobacco use (p=0.05), CEA elevation (p=0.0022), CNS metastases (p=0.01), male gender (p=0.08). There were no differences between stage IIIB, IV and CNS metastasis. The associated factors with survival by Cox proportional hazards regression multivariate analysis were poor performance status (p=0.05) and CEA elevation (p=0.008). The independent factors associated with CEA elevation were histology adenocarcinoma and brain metastasis. Patients with CEA >20 without neurological symptoms could benefit from early CT brain scan with stage IIIB and IV. In this group of patients, the 2 most important independent factors for survival were poor performance status and CEA elevation. No significant financial relationships to disclose.