Adjuvant endocrine therapy for breast cancer

Abstract

As reported by the Early Breast Cancer Trialists' Collaborative Group (EBCTCG) in Lancet (1992), the 10-year relapse-free survival or overall survival was significantly better in the tamoxifen (TAM) treatment group than in the control group in both node-positive and -negative groups. Adjuvant TAM treatment works better on patients over 50 years of age. Adjuvant TAM treatment for over 2 years is more effective than less than that time. Some reports demonstrated that long-term TAM treatment caused an increase in the circulating estrogen levels of premenopausal patients. This increase blocked the antitumor effect of TAM in a dose dependent fashion in our animal models. Similar results were obtained in toremifene or TAT-59 in our animal models. These results show that antiestrogens are more effective for postmenopausal than premenopausal women. LH-RH agonist or aromatase inhibitor may be a promising adjuvant endocrine agent of breast cancer. Combination therapy of TAM and LH-RH agonist, or LH-RH agonist and aromatase inhibitor will be an effective new adjuvant endocrine therapy for breast cancer. The combination of endocrine therapy and biological response modifiers, or of endocrine therapy with vitamin D3 will be clinically used in the future.