A compound having antiestrogenic activity is used in a method for the treatment of BC or other estrogen-responsive tumors in a human patient, wherein the method comprises subjecting the patient to a fasting mimicking diet for a period of 24-190 hours while the patient is being treated with the compound having antiestrogenic activity, which can be a selective estrogen receptor modulator (SERM), a selective estrogen receptor downregulator (SERD) or an aromatase inhibitor (AI).
