Journal of Clinical Oncology, Vol 16, 453-461, Copyright © 1998 by American Society of Clinical Oncology
Letrozole, a new oral aromatase inhibitor for advanced breast cancer: double-blind randomized trial showing a dose effect and improved efficacy and tolerability compared with megestrol acetate
P Dombernowsky, I Smith, G Falkson, R Leonard, L Panasci, J Bellmunt, W Bezwoda, G Gardin, A Gudgeon, M Morgan, A Fornasiero, W Hoffmann, J Michel, T Hatschek, T Tjabbes, HA Chaudri, U Hornberger and PF Trunet
PURPOSE: To compare two doses of letrozole and megestrol acetate (MA) as
second-line therapy in postmenopausal women with advanced breast cancer
previously treated with antiestrogens. PATIENTS AND METHODS: Five hundred
fifty-one patients with locally advanced, locoregionally recurrent or
metastatic breast cancer were randomly assigned to receive letrozole 2.5 mg
(n = 174), letrozole 0.5 mg (n = 188), or MA 160 mg (n = 189) once daily in
a double-blind, multicenter trial. Data were analyzed for tumor response
and safety variables up to 33 months of follow-up evaluation and for
survival up to 45 months. RESULTS: Letrozole 2.5 mg produced a
significantly higher overall objective response rate (24%) compared with MA
(16%; logistic regression, P = .04) or letrozole 0.5 mg (13%; P = .004).
Duration of objective response was significantly longer for letrozole 2.5
mg compared with MA (Cox regression, P = .02). Letrozole 2.5 mg was
significantly superior to MA and letrozole 0.5 mg in time to treatment
failure (P = .04 and P = .002, respectively). For time to progression,
letrozole 2.5 mg was superior to letrozole 0.5 mg (P = .02), but not to MA
(P = .07). There was a significant dose effect in overall survival in favor
of letrozole 2.5 mg (P = .03) compared with letrozole 0.5 mg. Letrozole was
significantly better tolerated than MA with respect to serious adverse
experiences, discontinuation due to poor tolerability, cardiovascular side
effects, and weight gain. CONCLUSION: The data show letrozole 2.5 mg once
daily to be more effective and better tolerated than MA in the treatment of
postmenopausal women with advanced breast cancer previously treated with
antiestrogens.
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