In the longest-running trial comparing tamoxifen with the aromatase inhibitor letrozole, results reveal that letrozole continues to prevent breast cancer recurrences and lower the risk of death in postmenopausal women with hormone receptor-positive early breast cancer.
Professor Richard Gelber, Director of the International Breast Cancer Study Group Statistical and Data Management Center at the Dana-Farber Cancer Institute, Boston, Massachusetts, reported at the 2011 European Multidisciplinary Cancer Congress* that, “over a median of 8 years of follow-up, women who were assigned to receive 5 years of letrozole after surgery had an 18% reduced risk of relapse and a 21% reduced risk of death compared with those assigned to receive tamoxifen.”
For the Breast International Group (BIG) 1ß-98 trial, 8010 patients received letrozole and tamoxifen either alone or in sequence. The monotherapy arms of the study included 4922 patients, or over half of the participants. Because the patients had a long-term risk of recurrence, every 2 years following the initial report of results, efficacy analyses comparing the treatment groups were conducted. The current 12-year update shows that, among all 8010 patients, there were 2074 relapses and 1284 deaths. In comparison, at the 10-year update there were 1569 relapses and 923 deaths.
”The current 12-year update is the longest follow-up to date and includes much more information than we had after 10 years. For instance, there have been 32% more relapses and 39% more deaths since the 10-year update, which increases substantially the reliability of the results and provides reassurance regarding the long-term value of letrozole. This additional follow-up and accumulation of information on relapses and deaths show that the overall survival advantage for adjuvant letrozole compared to tamoxifen continues to be statistically significant.”
“The data also show that the sequential use of letrozole and tamoxifen (2 years of 1 agent followed by 3 years of the other) provided similar outcomes compared with 5 years of letrozole alone for patients who are not at high risk for recurrence,” said Gelber.
He added, “Letrozole and tamoxifen have different side effects, and clinicians should consider the individual patient’s medical history when prescribing treatment. While long-term safety data are available for tamoxifen, follow-up of patients who have received letrozole or other aromatase inhibitors is still relatively short. Thus, assessment of the long-term safety of letrozole is a critical objective for the BIG 1-98 follow-up study.”
*The 2011 European Multidisciplinary Cancer Congress is the 16th congress of the European CanCer Organisation (ECCO), the 36th congress of the European Society for Medical Oncology (ESMO) and the 30th congress of European Society for Therapeutic Radiology and Oncology (ESTRO).
Source: ECCO