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Switching from tamoxifen to arimidex

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     Over and over again aromatase inhibitors were shown to be superior to tamoxifen in post-menopausal women with breast cancer. Anastrozole (Arimidex) has recently been shown superior to tamoxifen in this setting. The issue of switching those patients who are already on tamoxifen has been a major topic of study in the recent months or years. Switching from tamoxifen to exemestane (Aromasin) after 2 two three years of treatment has shown to give beneficial results (New England Journal of Medicine: March 11, 2004). Now there is new evidence to suggest that this is true with Anastrozole (Arimidex). These findings were published by American Society of Medical Oncology (ASCO) at their website.

    This study was conducted by researchers Francesco Boccardo and colleagues from Italy. The fact that tamoxifen is associated with increased risk of endometrial cancer and other life-threatening events and relatively inefficiency of tamoxifen in prevention of breast cancer recurrence led the researchers to explore other options. Francesco Boccardo and colleagues conducted a prospective randomized trial to test the efficacy of switching postmenopausal patients who were already receiving tamoxifen to the aromatase inhibitor anastrozole. Patients were randomly assigned to either receive anastrozole or continue tamoxifen after a period of 2 to 3 years of tamoxifen treatment for a total duration of treatment of 5 years. Disease-free survival was the primary end point. Event-free survival, overall survival, and safety were secondary end points.

    The study enrolled four hundred forty-eight patients and all women had node-positive, estrogen receptor-positive tumors. At the time of publication patients had a median follow-up time of 36 months. The group receiving anastrozole had significantly less adverse events compared to the group receiving tamoxifen. Disease-free and local recurrence-free survival were also significantly longer in the anastrozole group. More events were life threatening or required hospitalization in the tamoxifen group than in the anastrozole group.

    From the findings the authors have concluded that "switching to anastrozole after the first 2 to 3 years of treatment is well tolerated and significantly improves event-free and recurrence-free survival in postmenopausal patients with early breast cancer."