For post­menopausal women with endocrine-​​responsive early breast can­cer, letro­zole monother­apy pro­vides a greater reduc­tion in breast can­cer recur­rence and mor­tal­ity than tamox­ifen monother­apy, accord­ing to a new study.

After a median of eight years of follow-​​up from a large, ran­dom­ized trial, women who had received five years of treat­ment with letro­zole, an aro­matase inhibitor, were less likely to die or have their can­cer recur dur­ing follow-​​up than women who had five years of treat­ment with tamox­ifen. In addi­tion, five years of sequen­tial treatment—either two years of letro­zole fol­lowed by three years of tamox­ifen or two years of tamox­ifen fol­lowed by three years of letrozole—did not pro­duce bet­ter results than five years of letro­zole alone.

The study fol­lowed 8,010 post­menopausal women with inva­sive breast can­cer that had been removed sur­gi­cally. Women who received letro­zole alone had a disease-​​free sur­vival rate of 73.7% at eight years com­pared with a rate of 70.4% for women who received tamox­ifen alone. Women who receive letro­zole alone also had bet­ter over­all sur­vival at eight years than women receiv­ing tamox­ifen alone (83.4% ver­sus 81.2%).

Accord­ing to the authors, the two drugs have dif­fer­ent side effects, and this study shows that women have options. If the side effects from letro­zole are intol­er­a­ble, ben­e­fits are main­tained by switch­ing to tamox­ifen rather than stop­ping hor­monal ther­apy alto­gether. Novar­tis, the man­u­fac­turer of letro­zole, pro­vided fund­ing for the trial, along with the National Can­cer Insti­tute and the Inter­na­tional Breast Can­cer Study Group.

• Regan, M.M., Neven, P., Gioggie-​​Hurder, A., Gold­hirsch, A., Ejlert­sen, B. Mau­riac, L., . . . Thurli­mann, B. (2011). Assess­ment of letro­zole and tamox­ifen alone and in sequence for post­menopausal women with steroid hor­mone receptor-​​positive breast can­cer: The BIG 1–98 ran­domised clin­i­cal trial at 8·1 years median follow-​​up. Lancet Oncol­ogy, 12, 1101–1108. doi: 10.1016/S1470-2045(11)70270–4