Abstract Objective: Recurrent disease in stage I non-small cell lung cancer (NSCLC) is primarily attributed to metastatic dissemination at the time of surgery undetected by current staging practices. We hypothesized that metastatic progression is driven by epithelial-to-mesenchymal transition (EMT) resulting in differences in tumor-shed protein biomarkers. The objective of this study was to evaluate the difference in expression of these biomarkers in patients with recurrent stage 1 NSCLC. Methods: We used the Luminex immunobead platform, including the MILLIPLEX map human angiogenesis/growth factor magnetic bead panel, to evaluate 80 biomarkers related to EMT against a total of 75 patients who underwent a complete anatomic resection. Patients were divided into the following cohorts: a) stage I NSCLC without recurrence in 2 years (n=50), and b) stage I NSCLC with recurrence within 2 years of follow up (n=25). Peripheral blood was collected and processed using standard phlebotomy techniques. Specimens were obtained in compliance with institutional IRB standards and consent. The Mann-Whitney test and receiver operator characteristics (ROC) curves were used to assess differences in biomarker concentrations between cohorts. Results: Univariate analysis revealed 19 biomarkers with significant (ROC >0.6) differences in expression between the patient cohorts including: angiopoietin 2, MCP-1, MIP-IB, TNF-R1, IGFBP-5, VEGF-D, IGF-1, IGFBP-3, follistatin, sICAM-1, sE-SELECTIN, CYFRA 21.1, RANTES, IL-Ira, M-CSF, IGFBP-1, IGFBP-6, HB-EGF, and PGF. The Mann-Whitney test revealed five biomarkers highly significant (p<0.05) for recurrence in stage 1 NSCLC, including MCP-1, VEGF-D, follistatin, sICAM-1, and placental growth factor (PGF). Evaluation of these biomarkers with the Ingenuity Pathway Analysis (IPA) suite identified several highly significant (p<1x10−5) biological themes, including ten IPA-defined processes associated with development (e.g. embryonic development and cardiovascular system development), seven processes associated with pathological processes (e.g. cancer, cell death, and respiratory disease), and seven processes associated with metastasis (e.g. cellular movement, immune cell trafficking, and cell-to-cell signaling and interaction). Random Forest analysis generated a 6-analyte panel consisting of MCP-1, IP-10, sICAM-1, IGFBP2, RANTES, and IGFBP3 that provided 71.1% classification accuracy with 66.1% sensitivity and 73.3% specificity. Conclusions: Here we report observations concerning the expression of EMT pathway members that may provide key insights into the role of circulating biomarkers related to recurrence in stage 1 NSCLC. Upon further validation, these biomarkers may serve as convenient surrogates to help guide molecular diagnostics and treatment strategies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1730. doi:1538-7445.AM2012-1730