This study is for post-menopausal women with a certain type of early-stage breast cancer. It tests if a lower dose of a medicine called tamoxifen works as well as the usual hormone treatments. Tamoxifen stops the hormone estrogen from helping cancer grow. Other treatments, like aromatase inhibitors (e.g., anastrozole, letrozole, exemestane), also block estrogen but in a different way. The study wants to find out if taking less tamoxifen is just as good and safe. Participants are split into two groups: one gets the usual treatment and the other gets low-dose tamoxifen every other day. Both groups will take their treatments for up to 5 years and have regular check-ups, including mammograms and blood tests. They'll be checked for side effects like bone problems or blood clots. After finishing treatment, they'll be followed for 10 more years to see how they are doing.

• Study lasts up to 5 years with an additional 10-year follow-up.
• Participants will have regular check-ups, including mammograms and blood tests.
• Potential risks include bone issues and blood clots.