Updated project metadata. We compared the proteome of primary SqCLC tumor tissue between patients with ER (< 10 months) vs. LR (> 30 months) following surgery. iTRAQ-based quantitative 2D LC-MS/MS proteomics were performed on 20 SqCLC tumor samples (10 ER, 10 LR) using a matched pair design in which each ER tumor sample was paired and analyzed together with a LR tumor sample matched based on similar patient clinicopathologic features, including gender, smoking history, age and TNM status.