Professor Coombes said switching drugs also seemed to avoid the side-effects of long-term tamoxifen therapy, such as cancer of the womb and deep vein thrombosis.

BBC: Breast cancer drug 'cuts deaths'

Dr. WEINER: Around the world there are certainly many women who have been on tamoxifen for five years, have been off all therapy for a few years, and might consider going on a drug like letrozole or specifically letrozole based on these results.

NPR: Study: Drug Can Curb Breast Cancer Recurrence

Because hormone therapy is less toxic than chemotherapy, your doctor might start with tamoxifen or an aromatase inhibitor.

CNN: Recurrent breast cancer