Among postmenopausal women with early-stage, hormone receptor-positive breast cancer, five years of hormonal therapy with Femara® (letrozole) results in a lower risk of cancer recurrence than five years of tamoxifen. These results were published in Lancet Oncology.
The majority of breast cancers are hormone receptor-positive. These cancers are stimulated to grow by the circulating female hormones estrogen and/or progesterone. Treatment of hormone receptor-positive breast cancer often involves hormonal therapies that suppress or block the action of estrogen. These therapies include tamoxifen as well as drugs known as aromatase inhibitors, such as Femara. Tamoxifen acts by blocking estrogen receptors, whereas aromatase inhibitors suppress the production of estrogen in postmenopausal women.
The Breast International Group (BIG) 1-98 Trial is a Phase III clinical trial involving over 8,000 postmenopausal women with hormone receptor-positive early breast cancer. The women were assigned one of four different approaches to hormonal therapy:
- Five years of tamoxifen
- Five years of Femara
- Two years of Femara followed by three years of tamoxifen
- Two years of tamoxifen followed by three years of Femara
Previous results from this study showed that five years of Femara resulted in a lower risk of breast cancer recurrence than five years of tamoxifen, and that sequential treatment with the two drugs (Femara followed by tamoxifen or tamoxifen followed by Femara) did not appear to be superior to Femara alone.
Study participants continue to be followed in order to assess longer-term outcomes. The women have now been followed for a median of just over eight years.
- At eight years, the percentage of women alive and free of cancer was 73.8% among women assigned to five years of Femara and 70.4% among women assigned to five years of tamoxifen.
- Overall survival was 83.4% among women assigned to five years of Femara and 81.2% among women assigned to five years of tamoxifen.
- Sequential treatment with Femara and tamoxifen did not appear to be more effective than Femara alone.
For postmenopausal women with hormone receptor-positive breast cancer, these results continue to suggest that five years of Femara is more effective against breast cancer recurrence than five years of tamoxifen. Sequential treatment with the two drugs did not result in better outcomes than Femara alone, but may be a useful strategy for some women.
Reference: Regan MM, Neven P, Giobbie-Hurder A et al. Assessment of letrozole and tamoxifen alone and in sequence for postmenopausal women with steroid hormone receptor-positive breast cancer: the BIG 1-98 randomised clinical trial at 8.1 years median follow-up. Lancet Oncology. 2011;12:1101-1108.