Comparison of the efficacy of adjuvant letrozole and anastrozole in hormone-receptor positive postmenopausal breast cancer patients.

Abstract

e11554 Background: In the adjuvant hormonal treatment of postmenopausal breast cancer patients, most of the trials have showed the superiority of aromatase inhibitors over tamoxifen. However, there are limited data in the literature comparing the efficacy of aromatase inhibitors in postmenopausal women. Thus, the aim of this study is to compare the efficacy of letrozole and anastrozole in hormone-receptor positive postmenopausal breast cancer patients. Methods: Newly diagnosed breast cancer patients from 2001 to 2012 in our clinic were retrospectively analyzed. A total 566 hormone receptor-positive postmenopausal breast cancer patients were analyzed. The patients were divided into two group; anastrozole group (n=235) and letrozole patients (n=331). Kaplan–Meier survival analysis was carried out for disease free survival (DFS) and overall survival (OS). The log-rank test was used to examine the statistical significance of the differences observed between the groups. Results: The mean age was 59.2±8.5 in anastrozole group, and 60.1±8.4 in letrozole arm (P = 0.19). The mean BMI was 29.4±5.1 kg/m2 and 29.3±5.3 kg/m2 of anastrozole and letrozole arm, respectively (P =0.84). The median follow-up time for this analysis was 25.1 months. The histology of the primary tumor and type of surgery was similar and not statistically significant in both groups. Also in both arms the incidence of lymphovascular invasion, perineural invasion, HER2 positivity and histological grade were similar and not statistically significant. There were no apparent differences in baseline nodal status (P = 0.43), tumor size (P = 0.58) and tumor stage (P = 0.15) between two treatment arms. In anastrozole arm DFS rate was 93.7%, 81.3% and 66.0% whereas in letrozole arm DFS rate was 90.6%, 78.7% and 68.5% in the first, third and fifth years respectively. Median OS could not be obtained due to low events in both groups. Three year survival rate in anastrozole group was 98.8%, whereas in letrozole arm was 96.7% (P=0.84). Conclusions: In this retrospective study, the efficacy of letrozole and anastrozole was similar in hormone-receptor positive postmenopausal breast cancer patients.