However, the combination of CPT1A, CA15–3, CEA, and CA125 (training set: AUC, 0.904; 95% CI, 0.881–0.927, Fig. 5b, left; cross-validated AUC, 0.914; 95% CI, 0.880–0.948; Fig. S5F) did not significantly improve the classification capacity and diagnostic efficacy of breast cancer patients than CPT1A alone. Here, CEACAM5 is linked to breast cancer.