The present invention relates to the use of apolipoprotein A, a mimetic peptide thereof, or an activator thereof for the preparation of a medicinal product for the treatment or prevention of cancer. The invention also relates to a method for determining the stage of a colorectal tumor in a patient, where the method comprises determining ApoAl levels in a biofluid from said patient, wherein decreased ApoAl levels with respect to a reference value indicate a more advanced stage of the tumor, as well as a method for selecting treatment for a cancer patient, where the method comprises determining ApoAl levels in a biofluid from said patients, wherein decreased ApoAl levels with respect to a reference value indicate that the therapy of choice is a therapy based on apolipoprotein A, a mimetic peptide thereof, or an activator thereof.