I take my Vit D, Vit B and Krill Oil with my Arimidex at breakfast time.
If you are wanting to take any supplements during your treatment it is very important that you check with your oncologist. The whole point of chemo or radiation therapy is that it destroys cancer cells (and sadly lots of good cells too) and as appealing as it might sound you really don't want to take anything to counter this that hasn't been approved by your oncologist.