The extended adjuvant NCIC CTG MA.17 trials: initial and rerandomization studies

Based upon the results of the NCIC CTG MA.17 trial, letrozole has become the only approved aromatase inhibitor (AI) in the extended adjuvant treatment setting following 5 years of tamoxifen therapy. In this trial, the AI letrozole decreased the overall risk of breast cancer recurrence by 42% compared with placebo in postmenopausal women completing 5 years of tamoxifen. The benefit of letrozole exceeded the expected difference after median follow-up of more than 2 years and led to the unblinding of the trial. The 30-month updated analyses found a 4.8%, 4-year disease-free survival improvement overall, an improvement in distant disease-free recurrence in both node-negative and node-positive patients, and a survival benefit for node-positive patients. Generally well tolerated, letrozole caused some adverse events including arthralgias and osteoporosis. However, results from the Zometa-Femara adjuvant synergy trial (Z-FAST) suggest that zoledronic acid, when used concomitantly with letrozole, is able to manage bone loss in postmenopausal women with early breast cancer.