Doesn estrogen have an effect on breast cancer?
Yes, estrogen can promote an early breast cancer that is already present prior to starting estrogen therapy. There is no data demonstrating that estrogen causes (initiates or starts) a breast cancer. The difference between promotion and initiation is extremely important. Also, estrogen can only promote those breast cancers that are able to respond to estrogen…and these are usually the more “benign” cancers. This can also mean we are able to find these cancers sooner.
