Anti-EGFR-resistant clones decay exponentially after progression: implications for anti-EGFR re-challenge

Patients with KRAS/NRAS (RAS) wild-type metastatic colorectal cancer (mCRC) have improved survival when treated with anti-epidermal growth factor receptor (anti-EGFR) monoclonal antibodies. However, these agents do not benefit patients with oncogenic RAS mutations [1–4]. Though less common, alterations in BRAF/HER2 and MAP2K1 (MEK) are additional biomarkers of primary resistance to anti-EGFR [5–7].