title: Letrozole in advanced breast cancer: the PO25 trial.
abstract: Tamoxifen has been a standard first-line endocrine therapy for post-menopausal women with hormone-responsive advanced breast cancer, but more than half of patients fail to respond and time to progression is less than 12 months in responders. The third-generation aromatase inhibitors were developed to provide more effective alternatives to tamoxifen. In the Femara Study PO25, post-menopausal women with advanced breast cancer were randomized to receive letrozole 2.5 mg (n=453) or tamoxifen 20 mg (n=454) given orally daily until progressive disease occurred. Patients were permitted to cross over to the other treatment at progression. In the primary efficacy analysis, median time to progression (TTP) was significantly longer with letrozole than with tamoxifen (9.4 months vs. 6.0 months, respectively; P<0.0001). The objective response rate (ORR) was significantly higher for letrozole than for tamoxifen (32% vs. 21%; P=0.0002). Prospectively planned analyses of the intent-to-treat population showed that letrozole significantly improved overall survival (OS) compared with tamoxifen over the first 24 months of the trial. An exploratory analysis of patients, who did not cross over, indicated a median OS benefit of 14 months for letrozole compared with tamoxifen. Letrozole is the only third-generation aromatase inhibitor that has demonstrated significant improvements in ORR, TTP, and early OS.
authors.affiliation: Department of Oncology, Rigshospitalet, Copenhagen University Hospital, Blegdamsvej 9, 2100, Copenhagen, Denmark. hmouridsen@rh.dk
authors.forename: Henning T
authors.initials: HT
authors.lastname: Mouridsen
mesh_terms: D000368:Aged; D018931:Antineoplastic Agents, Hormonal / Q000627:therapeutic use*; D047072:Aromatase Inhibitors / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000473:pathology; D003362:Cost-Benefit Analysis; D018592:Cross-Over Studies; D018450:Disease Progression; D018572:Disease-Free Survival; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D000077289:Letrozole; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D009367:Neoplasm Staging; D009570:Nitriles / Q000627:therapeutic use*; D017698:Postmenopause; D011379:Prognosis; D011788:Quality of Life; D016019:Survival Analysis; D013629:Tamoxifen / Q000627:therapeutic use*; D016896:Treatment Outcome; D014230:Triazoles / Q000627:therapeutic use*
chemical_list: D018931:Antineoplastic Agents, Hormonal; D047072:Aromatase Inhibitors; D009570:Nitriles; D014230:Triazoles; D013629:Tamoxifen; D000077289:Letrozole