Skip to content

Breast Cancer Health Center

Font Size

Stage I, II, IIIA, and Operable IIIC Breast Cancer


    Three trials examined the effect of switching to anastrozole to complete a total of 5 years of therapy after 2 to 3 years of tamoxifen.[146,147,148] One study, which included 448 patients, demonstrated a statistically significant reduction in DFS (HR, 0.35; 95% CI, 0.18–0.68; P = .001) but no difference in OS.[146][Level of evidence: 1iiA] The other two trials were reported together.[147] A total of 3,224 patients were randomized after 2 years of tamoxifen to continue tamoxifen for a total of 5 years or to take anastrozole for 3 years. After a median follow-up of 78 months, an improvement in all-cause mortality (HR, 0.61; 95% CI, 0.42–0.88; P = .007) was observed.[148]

    A meta-analysis of these three studies showed that patients who switched to anastrozole had significant improvements in DFS (HR, 0.59; 95% CI, 0.48–0.74; P < .001), EFS (HR, 0.55; 95% CI, 0.42–0.71; P < .001), distant DFS (HR, 0.61; 95% CI, 0.45–0.83; P = .002), and OS (HR, 0.71; 95% CI, 0.52–0.98; P = .04) compared with the patients who remained on tamoxifen.[149]


    A large double-blinded randomized trial of 8,010 postmenopausal women with hormone receptor-positive breast cancer compared the use of letrozole versus tamoxifen given continuously for 5 years or with crossover to the alternate drug at 2 years.[150] In an updated analysis from the Breast International Group (IBCSG-1-98) including only the 4,922 women who received tamoxifen or letrozole for 5 years, at a median follow-up time of 51 months, DFS was significantly superior in patients treated with letrozole (HR, 0.82; 95% CI, 0.71–0.95; P = .007; 5-year DFS = 84.0% vs. 81.1%).[151][Level of evidence: 1iDii] OS was not significantly different (HR, 0.91; 95% CI, 0.75–1.11; P = .35). Patients on letrozole had significantly fewer thromboembolic events, endometrial pathology, hot flashes, night sweating, and less vaginal bleeding. Patients on tamoxifen had significantly fewer bone fractures, arthralgia, hypercholesterolemia, and cardiac events other than ischemic heart disease and cardiac failures.[151]


    Today on WebMD

    Breast Cancer Overview
    From self-exams and biopsies to reconstruction, we’ve got you covered.
    Dealing with breast cancer
    Get answers to your questions.
    woman having mammogram
    Experts don’t agree on all fronts, but you can be your own advocate.
    woman undergoing breast cancer test
    Many women worry. But the truth? Most abnormalities aren’t breast cancer.
    Breast Cancer Treatments Improving
    Resolved To Quit Smoking
    Woman getting mammogram
    Screening Tests for Women
    ovarian cancer overview slideshow
    serious woman
    what is your cancer risk
    10 Ways to Revitalize Slideshow