Targeting the insulin growth factor pathway in gastrointestinal cancers.

Insulin-like growth factor 1 (IGF-1)-directed therapy is currently at a crossroads. After decades of research, several agents targeting the IGF pathway are now in clinical trials. One recent phase III trial of the IGF-1R inhibitor figitumumab in patients with non-small-cell lung cancer was discontinued after an interim analysis showed no survival improvement. Clinical trials for patients with sarcoma have demonstrated impressive anti-tumor activity in cases where the IGF-1 pathway is activated, such as in Ewing sarcoma; however, acquired resistance has been common. Recently, randomized phase II trials combining IGF-1 R with epidermal grown factor receptor (EGFR) inhibition in colorectal cancer have been completed. Preclinical studies have indicated that several biomarkers may have potential predictive value. Studies of IGF-1R inhibitors in gastrointestinal cancers are currently ongoing in pancreatic, gastroesophageal, hepatocellular, and colorectal cancers. A critical analysis of prior work in this field and a rational strategy for maximizing success on the basis of biomarker use are necessary.