Just saw your post and read it because I also take Anastrozole daily. Can't address blood test question – just wanted to most sincerely wish you well.

Glori, Any abnormal test will set off alarm bells and anxiety. I'm sure that is how you're feeling with the higher than normal levels of cancer antigen 15-3 (CA15-3) in your recent blood test. But remember, it's just an indicator, signalling that further testing is necessary to find out IF anything is wrong. When do you see your oncologist to discuss the results and get further testing?

Welcome to Connect, @caroline41. You may be interested in joining this discussion on anastrozole:
– Concerned about the side effects of anastrozole https://connect.mayoclinic.org/discussion/i-completed-all-treatments-for-breast-cancer-but-now-i-am-supposed/

Just thought I’d throw this out there-my oncologist at Dartmouth-Hitchcock does not test routinely for cancer markers as he says the test is unreliable and has many false positives and false negatives. He has been over 30 years practicing, so he has a lot of experience to back his opinion. Hopefully your elevated levels are an example of this. Best wishes.

FYI- My oncologist with Mayo Clinic AZ doesn’t trust the tumor marker tests either, says too unreliable.

My oncologist doesn't put a lot of stock in tumor markers either. BUT she does order them every month. So I guess we just continue to keep an eye on them. She also is not a big fan of scans–mostly seems to favor how I feel. The only thing that makes me feel better about that is those are the same things that the specialist at Michigan says…

Based on my experience I would request the appropriate imaging. My ca-15 was regularly checked. At least annually. I had mastectomy and treatment in 2007. As time went on I reduced CT scans to every two years and had been on Tamoxifen for 10 years. Two years after stopping Tamoxifen, in 2020, at annual checkup CA-15 was slightly elevated. CT and bone scan was ordered which showed possible bone cancer in my pelvis. PET and biopsies confirmed. I am now on a treatment of Ibrance and Letrozole and a periodic infusion of Zometa. Usually bone pain is the first symptom of bone mets. I still do not have that. So without the tumor marker test and follow up I would not know. The research indicates that early detection of mets does not improve outcome. So why do the tumor marker test is their reasoning. Also there is variability in it. But if there is a baseline determined, I think it can be useful. Not for screening, but for reoccurrence. And personally, I am glad to be fighting it.

A rising CA 15-3 was the only indication me or my Oncologist had that something might be wrong. I felt great and all my other bloodwork was normal. But in fact, my cancer had progressed to metastatic. Without the early indicator of the CA 15 -3 we might have gone months or longer with the advancing cancer going unnoticed & untreated. I am grateful for the little bit of anxiety that resulted in an earlier diagnosis & an active treatment plan.