High ligand expression is a predictive marker for panitumumab therapy benefit on progression-free survival (PFS) in patients with RAS wild-type (wt) advanced colorectal cancer (CRC); conversely, patients with low ligand expression gained no benefit. This according to a study of ligand expression in tumors from 323 patients with CRC, including 220 with RAS wt CRC. Researchers found:

• High ligand expression was not prognostic for overall survival (HR=0.79) or for PFS (HR=0.93).

• For patients with RAS wt and high ligand expression, median PFS was 8.3 months (irinotecan with panitumumab) vs 4.4 months (irinotecan alone).

• In patients with RAS wt and low ligand expression, median PFS was 3.2 months (irinotecan with panitumumab) vs 4.0 months (irinotecan alone); interaction test results were significant.

• Less marked effects were seen for response rate and overall survival.

Citation: Seligmann JF, Elliott F, Richman SD, et al. Combined epiregulin and amphiregulin expression levels as a predictive biomarker for panitumumab therapy benefit or lack of benefit in patients with RAS wild-type advanced colorectal cancer. [Published online ahead of print February 11, 2016]. JAMA Oncol. doi: 10.1001/jamaoncol.2015.6065.