A Randomized Trial of Letrozole in Postmenopausal Women After Five Years of Tamoxifen Therapy for Early-Stage Breast Cancer

N Engl J Med. 2003 Nov 6;349(19):1793-802. doi: 10.1056/NEJMoa032312. Epub 2003 Oct 9.

Abstract

Background: In hormone-dependent breast cancer, five years of postoperative tamoxifen therapy--but not tamoxifen therapy of longer duration--prolongs disease-free and overall survival. The aromatase inhibitor letrozole, by suppressing estrogen production, might improve the outcome after the discontinuation of tamoxifen therapy.

Methods: We conducted a double-blind, placebo-controlled trial to test the effectiveness of five years of letrozole therapy in postmenopausal women with breast cancer who have completed five years of tamoxifen therapy. The primary end point was disease-free survival.

Results: A total of 5187 women were enrolled (median follow-up, 2.4 years). At the first interim analysis, there were 207 local or metastatic recurrences of breast cancer or new primary cancers in the contralateral breast--75 in the letrozole group and 132 in the placebo group--with estimated four-year disease-free survival rates of 93 percent and 87 percent, respectively, in the two groups (P< or =0.001 for the comparison of disease-free survival). A total of 42 women in the placebo group and 31 women in the letrozole group died (P=0.25 for the comparison of overall survival). Low-grade hot flashes, arthritis, arthralgia, and myalgia were more frequent in the letrozole group, but vaginal bleeding was less frequent. There were new diagnoses of osteoporosis in 5.8 percent of the women in the letrozole group and 4.5 percent of the women in the placebo group (P=0.07); the rates of fracture were similar. After the first interim analysis, the independent data and safety monitoring committee recommended termination of the trial and prompt communication of the results to the participants.

Conclusions: As compared with placebo, letrozole therapy after the completion of standard tamoxifen treatment significantly improves disease-free survival.

Publication types

  • Clinical Trial
  • Clinical Trial, Phase III
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Aged
  • Antineoplastic Agents / therapeutic use*
  • Antineoplastic Agents, Hormonal / therapeutic use
  • Aromatase Inhibitors
  • Breast Neoplasms / drug therapy*
  • Chemotherapy, Adjuvant
  • Double-Blind Method
  • Enzyme Inhibitors / therapeutic use*
  • Female
  • Humans
  • Letrozole
  • Middle Aged
  • Neoplasms, Hormone-Dependent / drug therapy*
  • Nitriles / therapeutic use*
  • Postmenopause
  • Quality of Life
  • Survival Analysis
  • Tamoxifen / therapeutic use
  • Triazoles / therapeutic use*

Substances

  • Antineoplastic Agents
  • Antineoplastic Agents, Hormonal
  • Aromatase Inhibitors
  • Enzyme Inhibitors
  • Nitriles
  • Triazoles
  • Tamoxifen
  • Letrozole