Background: Insulin-like growth factor-1 receptor (IGF1R) signaling is important in pancreatic ductal adenocarcinoma (PDAC) biology, but little is known regarding IGF1R expression and patient characteristics and outcomes. Methods: In 365 patients with resected PDAC, we evaluated IGF1R protein expression using IHC on whole-slide sections and IGF1R genomic status using next-generation sequencing. Associations of IGF1R expression, measured by H-scores incorporating staining intensity and proportion of positive tumor cells, with disease-free survival (DFS) and overall survival (OS) were evaluated in 317 and 321 patients, respectively, using Cox regression adjusting for known prognostic factors. Results: Higher IGF1R expression in tumor cells was associated with worse DFS comparing highest versus lowest expression tertiles [median DFS, 10.8 vs. 16.1 months; adjusted hazard ratio (HR), 1.73; 95% confidence interval (CI), 1.24–2.44; Ptrend ¼ 0.002] and worse OS (median OS, 17.4 vs. 25.8 months; HR, 1.39; 95% CI, 1.00–1.92; Ptrend ¼ 0.046). The association between high IGF1R expression and reduced DFS was identified primarily among patients with a preoperative body mass index ≥25 kg/m2 (HR, 4.27; 95% CI, 2.03–8.96, comparing extreme tertiles; Pinteraction ¼ 0.032). KRAS-mutant tumors had greater IGF1R expression, and IGF1R expression in tumor epithelium was inversely correlated with that in stromal cells. Mutations in IGF1R were infrequent, and no overt loss-of-function alterations were identified. Higher IGF1R expression was modestly associated with higher gene copy number (Pearson correlation coefficient ¼ 0.26, P < 0.001). Conclusions: Higher IGF1R protein expression was associated with worse patient outcomes in resected PDAC. Impact: IGF1R expression in PDAC represents a potential biomarker to guide patient selection for more aggressive, multidrug regimens in the adjuvant setting.
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