[An elderly patient with advanced breast cancer who responded to treatment with letrozole-a case report].

: An 85-year-old woman was diagnosed as having cancer of the left breast at another hospital in August 2008. As she was judged to be an unsuitable candidate for surgery and had dementia; therefore, she was followed-up without treatment. When the patient visited our hospital in March 2010, a hemorrhagic mass lesion, 5 cm in diameter, was observed in the left breast. We investigated the possibility of metastases and found that the tumor had infiltrated the chest wall, with metastases to the axillary and intrathoracic lymph nodes. Therefore, advanced breast cancer with left-sided pleural effusion and metastases to the pleura and bone was diagnosed. A needle biopsy revealed that the tumor was a ductal carcinoma, which was estrogen receptor(ER)positive, progesterone receptor(PgR)positive, and human epidermal growth factor receptor 2(HER2) (1+). Despite the presence of distant metastases, the patient's systemic condition was reasonably good. Therefore, she was judged to be suitable for some form of treatment, and treatment with letrozole was initiated. Six months after the start of treatment, the primary lesion decreased in size and pleural effusion disappeared. Three years later, the existing lesions have not increased in size and no new lesion has appeared. Endocrine therapy may be effective for the treatment of advanced hormone-sensitive cancers in elderly patients.