yes the CEA could fall even if the cancer is growing. this is because the CEA is not a completely accurate tool to tel you what is happening.
in general this shouldn't happen. In general, it should be increasing. but it could have already increased to some "max" value for the time and new inflamation of the growing tumors not change that detected level of inflamation overall for your body. THis would be high number for that individual that doesn't get any higher
There are also cases where folks have cancer, but the CEA doesn't go up at all or only goes up marginally. This is someone who doesn't get a high number normally, even if they have cancer.
the number can also change over a few weeks up and down for other reasons unrelated to the cancer, which causes problems in looking for a trend.
in general as one poster said, for every individual, over time the doc learn the numbers that appear to be the normal "high" values and the normal "low" values. but more importantly, they look a trend to going up as an early warning to do more imaging or otherwise look for cancer, while they look a trend gong down as a good thing that treatment is working (confirmed by imaging).
DX 2/07 mets liver/bone/brain/spleen
bone mets 5 times
GammaKnife brain lesion 1/08
SIRT Spheres rlobe 7/08 llobe 8/08
cyberknife brain 10/08
Brain surgery 1/09