Cardiovascular adverse events during adjuvant endocrine therapy for early breast cancer using letrozole or tamoxifen: Safety analysis of BIG 1-98 trial

Henning Mouridsen, Aparna Keshaviah, Alan S. Coates, Manuela Rabaglio, Monica Castiglione-Gertsch, Zhuoxin Sun, Beat Thürlimann, Louis Mauriac, John F. Forbes, Robert Paridaens, Richard D. Gelber, Marco Colleoni, Ian Smith, Karen N. Price, Aron Goldhirsch

Research output: Contribution to journalArticlepeer-review


Purpose: Previous analyses of adjuvant studies of aromatase inhibitors versus tamoxifen, including the Breast International Group (BIG) 1-98 study, have suggested a small numerical excess of cardiac adverse events (AEs) on aromatase inhibitors, a reduction in the incidence of hypercholesterolemia on tamoxifen, and significantly higher incidence of thromboembolic AEs on tamoxifen. The purpose of the present study is to provide detailed updated information on these AEs in BIG 1-98. Patients and Methods: Eight thousand twenty-eight postmenopausal women with receptor-positive early breast cancer were randomly assigned (double-blind) between March 1998 and May 2003 to receive 5 years of adjuvant endocrine therapy with letrozole, tamoxifen, or a sequence of these agents. Seven thousand nine hundred sixty-three patients who actually received therapy are included in this safety analysis, which focuses on cardiovascular events. AE recording ceased 30 days after therapy completion (or after switch on the sequential arms). Results: Baseline comorbidities were balanced. At a median follow-up time of 30.1 months, we observed similar overall incidence of cardiac AEs (letrozole, 4.8%; tamoxifen, 4.7%), more grade 3 to 5 cardiac AEs on letrozole (letrozole, 2.4%; tamoxifen, 1.4%; P = .001) - an excess only partially attributable to prior hypercholesterolemia - and more overall (tamoxifen, 3.9%; letrozole, 1.7%; P <.001) and grade 3 to 5 thromboembolic AEs on tamoxifen (tamoxifen, 2.3%; letrozole, 0.9%; P <.001). There was no significant difference between tamoxifen and letrozole in incidence of hypertension or cerebrovascular events. Conclusion: The present safety analysis, limited to cardiovascular AEs in BIG 1-98, documents a low overall incidence of cardiovascular AEs, which differed between treatment arms.

Original languageEnglish
Pages (from-to)5715-5722
Number of pages8
JournalJournal of Clinical Oncology
Issue number36
Publication statusPublished - Dec 20 2007

ASJC Scopus subject areas

  • Cancer Research
  • Oncology


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