A case of elderly breast cancer achieving partial response by letrozole with stable disease to anastrozole as neoadjuvant endocrine therapy
Kihara, M.; Miyauchi, A.
Gan to Kagaku Ryoho. Cancer and ChemoTherapy 35(4): 687-690
2008
ISSN/ISBN: 0385-0684 PMID: 18408446 Document Number: 618744
An 85-year-old postmenopausal woman had multiple lesions in her right breast. Core needle biopsy showed solidtubular carcinoma with positive hormone receptor (ER+++, PgR-). She refused surgery and was then treated with anastrozole as neoadjuvant endocrine therapy. After seven months of the treatment, all lesions were increased or unchanged. The clinical response was judged as stable disease. Letrozole was chosen for the next therapy. After ten months, reductions in the tumors were noted, and the clinical response was judged a partial response. No side effects were observed. These two drugs are nonsteroidal aromatase inhibitors, and it is considered there is a cross-resistance between them. However, several studies have revealed letrozole was significantly more potent than anastrozole in inhibiting aromatase activity in vitro and in inhibiting total body aromatisation in vivo. This may be related to a difference in effect between the two drugs. It is suggested that letrozole as second-line endocrine therapy may be effective for postmenopausal breast cancer even after anastrozole failure.