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Chirgwin J, Sun Z, Smith I, Price KN, Thürlimann B, Ejlertsen B, Bonnefoi H, Regan MM, Goldhirsch A, Coates AS. The advantage of letrozole over tamoxifen in the BIG 1-98 trial is consistent in younger postmenopausal women and in those with chemotherapy-induced menopause. Breast Cancer Res Treat 2012; 131:295-306. [PMID: 21892704 PMCID: PMC4802157 DOI: 10.1007/s10549-011-1741-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2011] [Accepted: 08/11/2011] [Indexed: 10/17/2022]
Abstract
Letrozole, an aromatase inhibitor, is ineffective in the presence of ovarian estrogen production. Two subpopulations of apparently postmenopausal women might derive reduced benefit from letrozole due to residual or returning ovarian activity: younger women (who have the potential for residual subclinical ovarian estrogen production), and those with chemotherapy-induced menopause who may experience return of ovarian function. In these situations tamoxifen may be preferable to an aromatase inhibitor. Among 4,922 patients allocated to the monotherapy arms (5 years of letrozole or tamoxifen) in the BIG 1-98 trial we identified two relevant subpopulations: patients with potential residual ovarian function, defined as having natural menopause, treated without adjuvant or neoadjuvant chemotherapy and age ≤ 55 years (n = 641); and those with chemotherapy-induced menopause (n = 105). Neither of the subpopulations examined showed treatment effects differing from the trial population as a whole (interaction P values are 0.23 and 0.62, respectively). Indeed, both among the 641 patients aged ≤ 55 years with natural menopause and no chemotherapy (HR 0.77 [0.51, 1.16]) and among the 105 patients with chemotherapy-induced menopause (HR 0.51 [0.19, 1.39]), the disease-free survival (DFS) point estimate favoring letrozole was marginally more beneficial than in the trial as a whole (HR 0.84 [0.74, 0.95]). Contrary to our initial concern, DFS results for young postmenopausal patients who did not receive chemotherapy and patients with chemotherapy-induced menopause parallel the letrozole benefit seen in the BIG 1-98 population as a whole. These data support the use of letrozole even in such patients.
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Affiliation(s)
- Jacquie Chirgwin
- Australian New Zealand Breast Cancer Trials Group, Newcastle, NSW, Australia
- Box Hill and Maroondah Hospitals, Monash University, Melbourne, VIC, Australia
| | - Zhuoxin Sun
- International Breast Cancer Study Group Statistical Center, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Ian Smith
- The Royal Marsden Hospital, Institute of Cancer Research, London, United Kingdom
| | - Karen N. Price
- International Breast Cancer Study Group Statistical Center, Frontier Science and Technology Research Foundation, Boston, MA, USA
| | - Beat Thürlimann
- Breast Center, Kantonsspital St. Gallen, St. Gallen, Switzerland
- Swiss Group for Clinical Cancer Research (SAKK), Bern, Switzerland
| | - Bent Ejlertsen
- Danish Breast Cancer Cooperative Group (DBCG), Rigshospitalet, Copenhagen, Denmark
| | - Hervé Bonnefoi
- Medical Oncology, Institut Bergonié, Université de Bordeaux, INSERM U916, FNCLCC (Unicancer), Bordeaux, France
| | - Meredith M. Regan
- International Breast Cancer Study Group (IBCSG) Statistical Center, Department of Biostatistics and Computational Biology, Dana-Farber Cancer Institute, Harvard School of Public Health and Harvard Medical School, Boston, MA, USA
| | - Aron Goldhirsch
- European Institute of Oncology, Milan, Italy
- Swiss Center for Breast Health, Sant’Anna Clinics, Lugano-Sorengo, Switzerland
| | - Alan S. Coates
- International Breast Cancer Study Group, University of Sydney School of Public Health, Sydney, NSW, Australia
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