A friend has been in remission from a breast cancer (sorry don't know more about it other than it is hormone sensitive but was cared for with surgery and chemo) - her oncologist switched her from tamoxifen to an aromatase inhibitor after five years (when she would be at menopause) -- and her moods have been awful. As I understand it - the AI's can really affect one's mood and so antidepressants are often prescribed- and, alas, my friend doesn't believe in antidepressants...or medicine in general - so we all suffer with her horrid moods. But I'm not a doctor or even remotely knowledgeable on oncology - so take this anecdote for what it is. But you are doing the right thing by asking your oncologist why it was prescribed - although it takes time to titrate up and to see if an SNRI is even the right choice for you. When in doubt - ask questions....and if you have side effects on something that you find intolerable - speak up...