An 83-year-old postmenopausal woman was referred to our hospital in order to get the treatment for ER positive advanced breast cancer (T4aN2M0, stage III b). The patient was diagnosed as the dissected aortic aneurysm and the hypertension. It was decided that an operation and chemotherapy would be too difficult with high existing risks. As a result, she was treated with anastrozole of PST, a 3rd-generation aromatase inhibitor, which led to the marked regression of the left breast cancer within a month. The cancer wasn't visualized after eighteen months. With the ongoing breast-hormone Therapy, no remote metastasis has been found after thirty months to this day. The patient hasn't experienced any adverse effects with the above-mentioned therapy. We concluded that the hormone (anastrozole) therapy as PST is a useful treatment for elderly postmenopausal woman with ER positive advanced breast cancer.