A combined analysis of three large clinical trials has confirmed that switching to the aromatase inhibitor Arimidex (anastrozole) after 2-3 years of adjuvant treatment with tamoxifen (Nolvadex®) improves survival among hormone receptor-positive, postmenopausal women with breast cancer. These results were reported at the 28th annual San Antonio Breast Cancer Symposium.
Historically, tamoxifen has been the standard agent used for hormonal therapy in postmenopausal women with hormone receptor-positive breast cancer. It is typically used for five years. Tamoxifen works by binding to estrogen receptors in a cell so that estrogen is unable to bind, which ultimately reduces its growth-stimulatory effects.
Aromatase inhibitors have produced improved outcomes with fewer side effects than tamoxifen in women with advanced breast cancer. These agents work by blocking the body’s ability to form estrogen.
Results from previous studies have indicated that switching to an aromatase inhibitor after 2-3 years of tamoxifen may provide benefit over remaining on tamoxifen for the historically recommended five years.
Researchers recently performed a combined analysis of three clinical trials to determine if benefits achieved in the single trials remained significant in a pooled population of patients.
All three studies in the combined analysis enrolled postmenopausal hormone receptor-positive breast cancer patients who were randomly assigned to receive either five years of tamoxifen or 2-3 years of tamoxifen followed by Arimidex. The three trials enrolled a total of 4006 women. Nearly all patients (93%) had 0-3 positive lymph nodes. Patients had undergone either breast-conserving therapy or mastectomy, and 7% of patients had received prior chemotherapy.
After a median of 30 months of follow-up, patients who switched to Arimidex had better outcomes:
- Risk of recurrence was reduced by 24%.
- Survival was improved by 29%.
- Survival without cancer recurrence was improved by 41%.
The researchers concluded that switching to Arimidex after 2-3 years of tamoxifen appears to improve outcomes in postmenopausal women with hormone receptor-positive breast cancer.
Reference: Jonat W, Gnant M, Boccardo F, Kaufmann M, Rubagotti A, Jakesz R. Switching from adjuvant tamoxifen to anastrozole in postmenopausal women with hormone-responsive early breast cancer: a meta-analysis of the ARNO 95 Trial, ABCSG Trial 8, and the ITA Trial. Program and abstracts of the 28th Annual San Antonio Breast Cancer Symposium; December 8-11, 2005; San Antonio, Texas. Abstract 18.