It is usually started after surgery or after the completion of radiation treatment. If you have chemotherapy after surgery, your treatment with Tamoxifen will start after you have finished the chemotherapy. You can take Tamoxifen with or without food, at any time during the day, but you should take it at the same time each day. Some breast cancers need the hormone oestrogen to grow. Oestrogen is used by the cell if it finds a receptor to join to.
Tamoxifen blocks the receptors in breast tissue and stops oestrogen from working.
This slows down or stops the growth of cancer. Currently the recommended length of Tamoxifen therapy is five years. Tamoxifen treatment can reduce the chance of breast cancer returning after breast surgery. . It acts against the effects of oestrogen in the breast but acts like oestrogen in other tissues. So it may also provide some of the beneficial effects of oestrogen - reducing the risk of heart disease by lowering cholesterol, and reducing the chance of osteoporosis.