Tamoxifen therapy for five years after surgery is the established treatment for postmenopausal women with hormone-sensitive breast cancer. However, its use is associated with several side effects including endometrial cancer and blood-clotting disorders. The ATAC study is an international collaboration which compared the safety and efficacy of tamoxifen with anastrozole alone and the combination of both drugs for 5 years. The 3-year analysis of these data were encouraging, suggesting that anastrozole could be a future treatment option (see Lancet 2002; 359: 2131-39).
Published today are the 5-year follow-up results of the ATAC study. They show how anastrozole, compared with tamoxifen: increased disease-free survival by over 10%; increased the time to disease recurrence by around 20%; reduced cancer spreading (distant metastases) by 14%, and reduced cancer occurring on the other breast by over 40%.
Fewer women given anastrozole stopped taking the tablets early compared with women given tamoxifen; anastrozole was associated with fewer side effects although bone fractures and joint pain were more common than among women given tamoxifen.
Lead investigator Anthony Howell (Christie Hospital NHS Trust, Manchester, UK) comments: "Results from studies evaluating aromatase inhibitors after 23 years or 5 years of adjuvant tamoxifen, compared with continuing tamoxifen, suggest that it is reasonable to switch patients currently on tamoxifen to an aromatase inhibitor. However, these new data from the ATAC trial suggest that it is not appropriate to wait to start an aromatase inhibitor. The higher rates of recurrence (especially in years 13), and the increased numbers of adverse events and treatment withdrawals associated with tamox
Contact: Joe Santangelo