Wow, 18% is unacceptable. I took tamoxifen for1 1/2 years then was switched to arimidex, which I am currently taking, because I had gone thru medically induced menopause. I never heard that number, but did see on my prescription sheet that uterine cancer could be a side effect. I rolled the dice, but honestly you don't know what to do and take faith that your doctors are doing the best thing for you at the time.
God Bless You and you are in my thoughts and prayers for a healthy future!