### instruction:
If you are a doctor, please answer the medical questions based on the patient's description.

### input:
My father was detected for cancer of colon in March 2010. Surgery was carried out and biopsy revealed stage III (T3 N2 Mx). CT Scan and Lung X Ray stated that cancer had not spread to the Liver, pancreas, spleen, lungs.Pre - Surgery CEA level was 20. Post operative Chemotherapy was carried out detailed as under:Oxaliplatin 85 mg/square metre in 250 ml of 5% Dextrose IVI over 2 hours on day 1.     Folinic acid 350 mg IVI in 5% Dextrose over 2 hours on day 1    5FU 400 mg/sq metre IV bolus on day 1    5FU 1200 mg/sq metre IVI in normal saline over 23 hours on day 1.    5FU 1200 mg/sq metre IVI in normal saline over 23 hours on day 2.     12 cycles at 2 weekly intervalsThe CEA levels were checked half way through the Chemotherapy and was 3.8. However now one month post completion of Chemotherapy, the CEA levels have shot up to 78. The CT scan however shows no abnormality. While the doctor has reccomended PET, i am confused as to why the CEA levels would have shot up and if there is any cause to worry and panic? Could this be indicative of cancer being in blood or any other organ?

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HiT hanks for askingBased on your query my opinion is1. Casino embryonic antigen/ CEA is a protein which is normally detected in fetal gut tissue.2. Its levels decrease and very low levels are detected after birth.3. CEA levels can be elevated in both benign and malignant diseases, so it is not used for screening of colorectal cancer. 4. Its use is limited to determining the prognosis and monitoring the response of tumor to therapy.5. In your fathers' case the levels started to fall during treatment which is a good sign suggesting of response to therapy.6. However, rising levels following treatment is quite alarming, indicates recurrence or possibility of metastasis which needs to be further investigated.7. If recurrence or metastasis is not found then other benign causes like cirrhosis/ peptic ulcer/ hepatitis/ colitis needs to be looked for Hope this helpsRegards