Medicine has long drawn a single line through the KRAS gene, treating all mutations as one verdict: resistant. A study published in Nature now asks whether that line was drawn too broadly, finding that colorectal cancers carrying the G13 variant of KRAS respond to anti-EGFR antibody therapy much as unmutated tumors do — while G12-mutant tumors remain resistant. In the slow work of precision oncology, this distinction is not merely academic; it is the kind of refinement that determines which patients are offered a chance at treatment and which are quietly turned away.