I have been on anastrozole since 13 December, so Nearly 6 weeks. My cancer boob was certainly sore and I kept getting pains and occasionally in the other one. My sensible self thought it must have been radiation effects coming up again but my other self thought (of course) that it was the cancer spreading/recurring etc. i got my guts up and for the first time rang a support line on Thursday..the mcgrath nurse one and she told me it was the anastrozole. That hadn’t occurred to me. I had just focused on the bone/joint pain and tiredness. And the boob pain is just about gone now as well.