CA27.29 while on Femara

I was on Femara for four months. My CA27.29 went down consistantly from 180 to 51, but now it jumped back up to 71 within a month.  Could this reading be an error or can the marker results reverse that quickly (119 to 51 to 71 in two months)??

I stopped Femara a few weeks ago since the marker went up and I was in so much bone pain mainly in the rib area. My onc wants to start shots of Faslodex?  Could switching to Armidex be better. I read where sometimes switching from Femara to Armidex may have less pain and might be just as effective.

[PaulMD]

Hi there.

Switching from femara to arimidex may not do much of a difference since bone pains are also a common side effect of arimidex.  Furthermore, these two drugs are of the same class and is not likely to have an effect on the markers.  Faslodex, on the other hand, may be a more reasonable choice.

My take on the CA27.29 is that this marker has still of questionnable clinical utility. meaning, elevated levels of this marker does not really translate into the cancer being more aggressive.  It is best to have yourself re-evaluated for other signs of the cancer returning such as CT scans or other imaging studies (PET scan) to see if this elevation in CA 27.29 is indeed significant.

Regards.