KRAS and neoplasm: This would have been of particular interest since it has been proven that primary tumor location also has a predictive value.2,41 Post hoc analyses of clinical trials demonstrated an association between PTL and responsiveness to anti-EGFR therapy with patients with left-sided KRAS wild-type mCRC experiencing a significantly improved survival compared to patients with right-sided tumors.10,13,31,42,43 Another potential drawback of this study is the fact that only patients with synchronous metastatic disease were included.