['The insulin-like growth factor 1 receptor (IGF1R) is widely expressed in normal tissues and many malignancies in humans. We investigated the clinical significance of the expression of the IGF1R gene in human lung adenocarcinoma.', 'A total of 238 patients with lung adenocarcinoma were investigated. Quantitative real-time reverse-transcription polymerase chain reaction (RT-PCR) assays were performed to evaluate the gene expression of IGF1R, and immunohistochemical staining was done to evaluate the protein expression of IGF1R.', 'Among the 238 patients with lung adenocarcinoma, 107 tumors (45.0%) were IGF1R-low and 131 tumors (55.0%) were IGF1R-high. The IGF1R gene expression ratio was significantly lower in moderately to poorly differentiated adenocarcinomas than in well-differentiated adenocarcinomas (P = 0.0388). Gene expression of IGF1R was significantly correlated with protein expression of IGF1R (r = 0.7163, P < 0.0001). Regarding patient survival, overall survival was significantly lower in patients with IGF1R-low tumors than in those with IGF1R-high tumors (63.2% versus 76.1% 5-year survival, P = 0.0188). Multivariate analysis using a Cox proportional-hazards model demonstrated that IGF1R gene status was a significant prognostic factor predicting overall survival of patients with lung adenocarcinoma (hazard ratio 1.800; P = 0.0321). Moreover, the disease-free survival rate was significantly lower in patients with IGF1R-low tumors than in those with IGF1R-high tumors (49.2% versus 64.6% 5-year survival, P = 0.0084).'] Is expression of IGF1R associated with tumor differentiation and survival in patients with lung adenocarcinoma?