Hi Carolyn. Hope this reply isn't too late but I am currently on Tamoxifine post radiation and surgery. I had DCIS so not the full blown C but need to take it for three years as was Estrogen +ve so needs to be suppressed so nothing grows back. `I was very gutted as had been going through peri menopause for 2 years sorted out the symptoms and was on HRT but had to stop it immediately. I would say give it a go and if it doesn't work or things need to be reviewed then your medical oncologist will be able to help and advise and change it up. I went to my med O recently as felt the Tamoxifine was causing me to have night sweats and insomnia and she gave me something to help that as well as taking the Tamoxifine. It's well known to possible trigger peri but I have been advised it's best to take it to keep everything at bay. I would say it's worth the risk to do it and see and then make decisions on how you then feel.