Cea blood test levels low but cat scans show more cancer?

Not uncommon: Sometimes in poorly differentiated tumors, the CEA may not be elevated. That makes it difficult to follow because ct scans are utilized for monitoring. Hope this helps.

Possible: Please note that CEA is just another tool we have and as such it is not perfect. Many patients have elevated CEA and have no cancer and many others have clinical and x-ray evidence of active cancer and yet their CEA is normal. Such tumors just don't produce CEA and in those cases, the test is useless. No test is infallible.