My mother had a lump on her breast in which they said was not cancerous, but was hairline cancer. Both her parents family had cancer in them (breast: mother and aunt). Her cancer doctor wants to put her on Tamoxifen and I have been reading the studies and it worried me deeply. My question is actually how well does it work to prevent cancer and how long after the 5 years on average will she be cancer free? Also is Femara a better choice, she has had a heart attck with open surgery. Thank you very much for your time!!!!