CEA Tumor Marker Test Range?

Hi. Someone I know is going through cancer treatment (colorectal). His CEA score started at 12, went down to 6.5, and is now up to 25. Other than it going in the wrong direction, what do scores really mean? What is the possible range on the CEA tumor marker scale? Does it go up to 100, 1000, forever? Is... show more Hi.

Someone I know is going through cancer treatment (colorectal). His CEA score started at 12, went down to 6.5, and is now up to 25. Other than it going in the wrong direction, what do scores really mean? What is the possible range on the CEA tumor marker scale? Does it go up to 100, 1000, forever? Is there any correlation between # and prognosis or is it just that if it goes up, it's not good?

Thanks!
Update: The tumor has not been removed, he's unable to have additional CT scans due to an allergic reaction to the chemicals used for that process, and he is presently doing chemo only (no radiation therapy yet).
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