Hi Jen
This is my first post since being diagnosed with MBC back in February 2016. But reading your post today made me feel ashamed for not contributing to the online discussions. So, here's my tuppence worth of advice. I am currently on the same treatment as you and the itchy arms were unbearable at times. Application of cold packs was the only relief for me. I was also taking Frusemide (to shift excess fluid). I stopped the Frusemide and not long after the itchiness disappeared! Not sure if that was related or not but I now only get occasional itchiness that doesn't worsen when I scratch. I also reduced the number of hot baths I was having (that was hard...I love my bath time).
Good luck. I hope your situation improves with time as mine did.
Julie