Researchers affiliated with the Breast International Group recently reported that the drug Femara® is superior to Nolvadex® (tamoxifen) for the treatment of hormone receptor positive breast cancer. Details of the interim results of the study were recently presented at the 2005 meeting of the American Society of Clinical Oncology.
When breast cancer-a malignancy associated with tissues of the breast-is diagnosed, various tests are performed to further describe the cancer. One of these tests determines if cancer development was supported by the hormones estrogen and progesterone. Estrogen or progesterone positive cancers can be treated with drugs that prevent the hormones from reaching the breast cancer cells. Nolvadex has long been the standard for hormonal treatment of breast cancer, however as other types of drugs such as Femara have been developed, research now focuses on which sequences of these drugs provide the best overall outcomes.
In this recent international study, researchers enrolled 8000 postmenopausal women diagnosed with early stages of hormone receptor breast cancer. Each patient was randomized to receive hormone therapy within five years of surgery. The women received one of the following courses of drugs: Nolvadex for five years; Femara for five years; Nolvadex for two years followed by Femara for three; Femara for two years followed by Nolvadex for 3 years. An interim analysis was conducted after 26 months of follow up. Results of the study indicate that patients treated with Femara had a higher disease-free survival rate-84 percent were cancer-free at five years versus 81 percent. Femara patients also showed a reduced risk of recurrence and metastasis to a distant location (19 percent and 27 percent, respectively). Women who were at high risk for recurrent disease achieved the greatest benefit. This included women who had positive lymph nodes and those who had received chemotherapy due to the characteristics of their disease. In addition, other end points that favored Femara over Nolvadex included overall survival, disease free survival, and time to recurrence. Side effects were reported in both groups: cardiac related events and elevated cholesterol levels in the Femara group; clots, endometrial tissue changes and biopsies for those taking Nolvadex.
Researchers were encouraged by the benefits of Femara over Nolvadex, but acknowledge that longer follow-up is necessary to learn the full benefit of aromatase inhibitors and the possible risks.
Reference: Thurlimann B, Keshaviah A, Mouridsen H, et al. BIG1-98: Randomized double blind phase III study to evaluate letrozole vs. tamoxifen as adjuvant endocrine therapy for postmenopausal women with receptor positive breast cancer. Proc Am Soc Clin Oncol. 2005; 23: Abstract #511.