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| |  Letrozole Superior to Tamoxifen in Hormone Receptor-Positive Early Breast Cancer: Presented at SABCS By Jill Stein SAN ANTONIO, Tex -- December 11, 2009 -- Updated results of a major trial confirm that letrozole confers a significant survival benefit over tamoxifen when used after surgery in postmenopausal women with hormone receptor-positive early breast cancer, researchers announced here on December 10 at the 32nd Annual San Antonio Breast Cancer Symposium (SABCS). The results were drawn from an Inverse Probability of Censoring Weighted (IPCW) analysis that was undertaken to clarify the clinical benefit of letrozole compared with tamoxifen in the Breast International Group (BIG) 1-98 study. Earlier findings of that study, which were based on an intent-to-treat (ITT) analysis, were released at last year’s SABCS meeting. Meredith Regan, ScD, Harvard Medical School, Boston, Massachusetts, noted that the IPCW analysis shows that the benefit of letrozole over tamoxifen is larger than that shown in the ITT analysis. “In fact, BIG 1-98 provides evidence of a statistically significant [P < .05] overall survival benefit for 5 years of letrozole compared with 5 years of tamoxifen therapy,” she said. The BIG 1-98 study included 8,010 postmenopausal women who had completed surgery for oestrogen-sensitive breast cancer and who had no evidence of metastasis. Patients were randomly assigned to receive tamoxifen monotherapy for 5 years; letrozole monotherapy for 5 years; tamoxifen for 2 years followed by letrozole for 3 years; or letrozole for 2 years followed by tamoxifen for 3 years. The trial demonstrated the superiority of letrozole over tamoxifen in improving disease-free survival and decreasing the risk of recurrence in postmenopausal women with hormone receptor-positive early breast cancer. Dr. Regan said that the 2008 results from the ITT analysis and censored analyses were possibly influenced by the selective crossover that occurred when some patients receiving tamoxifen crossed over to letrozole, the more effective treatment, after disease-free survival results were initially presented in 2005. The IPCW analysis presented at this year’s meeting offers an estimate of the clinical benefit of letrozole that might have been observed had there been no selective crossover in the trial. The results revealed that letrozole treatment for 5 years after surgery significantly boosted disease-free survival by 15% (P < .05) and overall survival by 17% (P < .05). In a press release, Alan Coates, MD, Scientific Committee of the International Breast Cancer Study Group, which coordinated the BIG 1-98 trial, and the University of Sydney, Sydney, Australia, said: “Allowing patients to cross between arms of a clinical trial when one treatment demonstrates statistically superiority over another is ethical and appropriate, and can lead to better outcomes for those patients.” Dr. Coates was quick to add, however, that the standard ITT analysis is weakened by selective crossover, thereby underscoring the need for reliable statistical methods like IPCW in order to best determine clinical decision-making. Funding for this study was provided by Novartis. [Presentation Title: Adjusting for Selective Crossover in Analyses of Letrozole (Let) Versus Tamoxifen (Tam) in the BIG 1-98 Trial. Abstract 16]
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