Abstract
Abstract Background: Neoadjuvant endocrine therapy has been increasingly employed in clinical practice to improve surgical options for postmenopausal women with bulky hormone receptor-positive breast cancer. Recent studies indicate that tumor response and in particular the pathologic complete response (CR) in this setting may predict long-term outcome. The letrozole approval in neoadjuvant setting is based on a study that included 4 months of letrozole treatment only. Prospective studies have not investigated treatment duration beyond 6 months, and retrospective studies suggest that useful responses can occur after this period. The purpose of this study was to determine the clinical and pathologic response of 2.5 mg daily letrozole used with different schedule in breast cancer patients (pts) unfit for chemotherapy. Patients and Methods: This single Institution retrospective study comprised 102 postmenopausal women with primary breast cancer (clinical stage ≥T2, N0-1), who were divided into 3 subgroups (34 each in single subgroup) according to the different duration of neoadjuvant letrozole treatment: 4 months (subgroup A), 8 months (subgroup B) or 12 months (subgroup C) of treatment. The subgroups were comparable in terms of baseline characteristics. Results: Pts and tumor characteristics included: median age 77.3 years (range 53.9–95.4); 100% estrogen receptor-positive, 81.4% progesterone receptor-positive; median Ki67 13.5% (range 2–90%). All pts were evaluable for clinical and pathologic response. A total of 77 pts (75.5%) achieved an objective response at individual end: 40 (39.2%) clinical CR and 37 (36.3%) partial responses (PR). The clinical CR were significantly confined to subgroups C (20/34 pts, 58.8%) and B (16/34 pts, 47.1%) than to subgroup A (4/34 pts, 11.8%) (p for trend = 0.00001). Objective response rate was 46.1% (47/102 pts) at month 4, 83.8% (57/68 pts) at month 8, and 94.1% (32/34 pts) at month 12 compared with baseline. As expected, letrozole induced a significant reduction of Ki67 expression after treatment in any single subgroup, without significant differences between them. With very interest, the pathologic CR rate was significantly higher in subgroup C (7/34 pts, 20.6%) than in subgroups A (1/34 pt, 2.9%) and B (1/34 pt, 2.9%) (p for trend <0.02). Conclusions: One-year neoadjuvant letrozole therapy can lead to a high pathologic CR rate. This observation suggests that pathologic CR may be a reliable endpoint after endocrine therapy, but a long-term drug exposure is needed. The optimal letrozole treatment duration in neoadjuvant setting is a matter of future research. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr PD07-03.
Published Version
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