<s>[INST] My father os a cancer patient( colon cancer stage b2), he is done with his 5 cycles of chemotherapy , but his recent tests shows that his CEA level is increased to 8.7 fron 3.7 within 2 months, but my concerned doctors dnt find it a reason to worry,, what may be the reason for such significant rise please Advise me if there issomething serious [/INST] Hello! Thank you for the query. CEA level is used to control possible colon cancer regrow or metastases appearance. If the person who has colon cancer history gets increased CEA level, possible metastases should be localized or ruled out. So this should be the reason of concern. Moreover, B2 stage gives high rate of survivals, so it is necessary and worth to keep looking. The best way to do that is PET scan which will localize possible metastases. If this test is not available for your father, chest and abdominal CT with contrast should be performed. Hope this will help. Regards. </s>