Preoperative treatment of postmenopausal breast cancer patients with letrozole: A randomized double-blind multicenter study

Background: A randomized, double-blind, multicenter study was conducted to compare the anti-tumor activity of letrozole vs. tamoxifen in postmenopausa l women with ER and/or PgR positive primary untreated breast cancer. Patients and methods: Three hundred thirty-seven postmenopausal women with ER and/or PgR positive primary untreated breast cancer were randomly assign ed once daily treatment with either letrozole 2.5 mg or tamoxifen 20 mg for four months. At baseline none of the patients were considered to be candid ates for breast-conserving surgery (BCS) and 14% of the patients were consi dered inoperable. The primary endpoint was to compare overall objective res ponse (CR + PR) determined by clinical palpation. Secondary endpoints inclu ded overall objective response on ultrasound and mammography and the number of patients who qualified for BCS. Results: Overall objective response rate (clinical palpation) was statistic ally significantly superior in the letrozole group, 55% compared to tamoxif en, 36% (P < 0.001). Secondary endpoints of ultrasound response, 35% vs. 25 % (P = 0.042), mammographic response, 34% vs. 16% (P < 0.001), and BCS, 45% vs. 35% (P = 0.022) between the letrozole and tamoxifen groups, respective ly, showed letrozole to be significantly superior. Both treatments were wel l tolerated. Conclusions: This study shows that letrozole is more effective than tamoxif en as preoperative therapy in postmenopausal patients with ER and/or PgR po sitive primary untreated breast cancer and is at least as well tolerated.