Since research has reported that cellular and humoral immunodeficiency, which may be caused by stress and depression in breast cancer patients, could produce resistance to hormone therapy and often correlates with a poor prognosis, we checked these indices during the 6-month endocrine treatment period and found that CD4 was inhibited and the tumor growth markers, VEGF and CEA, levels improved. This evidence concerns the gene CEACAM5 and major depressive disorder.