The present invention relates to a method of treating or preventing estrogen-suppressed tumors in a mammal, said method comprising the administration of a therapeutically effective amount of an estrogenic component to said mammal, wherein the estrogenic component is selected from the group consisting of:substances represented by the following formula in which formula R1, R2, R3, R4 independently are a hydrogen atom, a hydroxyl group or an alkoxy group with 1-5 carbon atoms; precursors capable of liberating a substance according to the aforementioned formula when used in the present method; and mixtures of one or more of the aforementioned substances and/or precursors. The estrogenic component according to the invention is particularly useful in the treatment or prevention of colorectal and prostate cancer and, unlike commonly used estrogens, does not simultaneously enhance the risk of estrogen-stimulated cancers such as breast cancer.