Content area
Full Text
Breast Cancer Res Treat (2012) 131:295306 DOI 10.1007/s10549-011-1741-6
BRIEF REPORT
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
Jacquie Chirgwin Zhuoxin Sun Ian Smith Karen N. Price Beat Thrlimann
Bent Ejlertsen Herv Bonnefoi Meredith M. Regan Aron Goldhirsch
Alan S. Coates for the BIG 1-98 Collaborative and International Breast Cancer Study Groups
Received: 9 August 2011 / Accepted: 11 August 2011 / Published online: 4 September 2011 Springer Science+Business Media, LLC. 2011
Abstract Letrozole, an aromatase inhibitor, is ineffective in the presence of ovarian estrogen production. Two sub-populations of apparently postmenopausal women might derive reduced benet 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 mono-therapy arms (5 years of letrozole or tamoxifen) in the BIG 1-98 trial we identied two relevant subpopulations:
patients with potential residual ovarian function, dened as having natural menopause, treated without adjuvant or neoadjuvant chemotherapy and age B55 years (n = 641); and those with chemotherapy-induced meno-pause (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 B55 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 benecial than in the trial as a whole (HR 0.84 [0.74, 0.95]). Contrary to our initial
The participants of the BIG 1-98 Collaborative and International Breast Cancer Study Groups are given in Appendix.
J. Chirgwin (&)
Australian New Zealand Breast Cancer Trials Group, Newcastle, NSW, Australiae-mail: [email protected]
J. ChirgwinBox Hill and Maroondah Hospitals, Monash University, Melbourne, VIC, Australia
Z. SunInternational Breast Cancer Study Group Statistical Center, Dana-Farber Cancer Institute, Boston, MA, USAe-mail: [email protected]
I. SmithThe Royal Marsden Hospital, Institute of Cancer Research, London, United Kingdome-mail: [email protected]
K. N. PriceInternational Breast Cancer Study Group Statistical Center, Frontier Science and...