title: 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.
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.
authors: Australian New Zealand Breast Cancer Trials Group, Newcastle, NSW, Australia. chirgwin@tpg.com.au
authors: Jacquie
authors: J
authors: Chirgwin
authors: Zhuoxin
authors: Z
authors: Sun
authors: Ian
authors: I
authors: Smith
authors: Karen N
authors: KN
authors: Price
authors: Beat
authors: B
authors: Thürlimann
authors: Bent
authors: B
authors: Ejlertsen
authors: Hervé
authors: H
authors: Bonnefoi
authors: Meredith M
authors: MM
authors: Regan
authors: Aron
authors: A
authors: Goldhirsch
authors: Alan S
authors: AS
authors: Coates
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D018931:Antineoplastic Agents, Hormonal / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use; D047072:Aromatase Inhibitors / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000188:drug therapy*; D018572:Disease-Free Survival; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D000077289:Letrozole; D008593:Menopause; D008875:Middle Aged; D009570:Nitriles / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use; D017698:Postmenopause; D013629:Tamoxifen / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use; D014230:Triazoles / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use
chemical_list: D018931:Antineoplastic Agents, Hormonal; D047072:Aromatase Inhibitors; D009570:Nitriles; D014230:Triazoles; D013629:Tamoxifen; D000077289:Letrozole