7501 Background: A phase II randomized trial in 182 patients (pts) with completely resected stage IB or II MAGE-A3 (+) NSCLC comparing postoperative MAGE-A3 recombinant protein combined with an Adjuvant System to placebo (q3w x 5, followed by q3m x 8) showed a strong positive signal for activity (J Clin Oncol 25 Suppl 18:398S, 2007). We report here the analysis of gene expression profiling of tumors prior to treatment to identify a predictive signature that correlates with clinical activity of MAGE-A3 ASCI treatment. Methods: Microarray analysis (Affymetrix) was performed on 159 fresh-frozen tumor biopsies (MAGE-A3: 108; placebo: 51; stage IB: 109; stage II: 50). Clinical data on relapse are based on a median follow-up of 44 months. Results: Study of tumor samples from pts in the placebo arm led to identification of a gene signature associated with a high risk of postoperative relapse. The absence of this signature correlated with a very low relapse rate in stage IB pts: placebo 0%; MAGE-A3: 4%. In the MA...