Not sure why he says you must make an immediate change. I’m 19 years postmenopause and am taking tamoxifen. I think you’re right that AIs reduce estrogen to a much lower level throughout the body than tamoxifen.

AIs have a slightly better response to preventing a recurrence. For myself, I didn’t want the effects of the AI and chose tamoxifen, the risk levels were very close between the two.

Maybe there is an issue with tamoxifen as your body adjusts to the surgery? Maybe a hormone therapy holiday would be okay during that time? Then resume tamoxifen?

After reading so many posts by so many people it seems that some oncologists require the use of AIs because they do have a “significant” better response. But that statistically significant number is VERY low. Many of the research articles I’ve read have said the difference is so close as to not make a real difference. A drug choice should, of course, consider the top med options but should also include the patient’s individual body issues and their life choices.

One big issue though is whether you are at risk for deep vein thrombosis and endometrial cancer. If those risk levels will be high in postmenopause, then tamoxifen would not be a good choice.