However, a national retrospective study showed that only 18% of patients with AF and cancer had major bleeding when NOACs were combined with antitumor drugs with inhibitory or competitive effects on CYP3A4 or P-gp activity, which may be explained by the use of low-dose NOACs and cancer-related hypercoagulability (131). Here, CYP3A4 is linked to atrial fibrillation.