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BIG 1-98: Benefits of letrozole over tamoxifen greater than previously reported
San Antonio Breast Cancer Symposium
Further analysis of the BIG 1-98 trial indicated that five years of treatment with the aromatase inhibitor letrozole resulted in longer disease-free survival and OS compared with treatment with tamoxifen.
Meredith Regan, ScD, assistant professor of medicine at Harvard Medical School, presented the results at the San Antonio Breast Cancer Symposium. She said selective crossover of about 25% of patients in the tamoxifen group biased previously released data.
“Our best estimate is that five years of letrozole monotherapy is significantly better than tamoxifen for DFS, OS and time to distant recurrence,” she said.
Regan and colleagues performed an inverse probability of censoring weighted (IPCW) analysis on results from BIG 1-98, a phase-3, randomized, multicenter trial comparing letrozole (Femara, Novartis) vs. tamoxifen.
Results from BIG 1-98 presented in 2008 showed a nonsignificant 13% reduction in the risk for death associated with letrozole in the intent-to-treat population. The censored analysis, which included patient data only up to time of crossover, showed an OS benefit associated with letrozole (19%; HR=0.81; 95% CI, 0.68-0.96).
The IPCW analysis, which estimated the benefit associated with letrozole had there been no crossover, showed that five years of treatment with letrozole after surgery improved DFS by 15% (95% CI, 0.75-0.95) and OS by 17% (95% CI, 0.71-0.97).
“Because of selective crossover and based on external evidence on the benefit of switching from tamoxifen to aromatase inhibitor, the ITT analysis on updated data from BIG 1-98 is not accurate and is no longer relevant for patient care,” Regan said. – by Jason Harris
For more information:
- Regan M. #16. Presented at: the 32nd Annual CTCR-AACR San Antonio Breast Cancer Symposium; Dec. 9-11, 2009; San Antonio, Texas.
