Hello doctor my husband was diagnosed with colon cancer in August 2019 after which he had a surgery and chemo he had T3n1c M0 disease after the surgery and before chemos his CEA level was 2.33 After chemo in month of May it was 5.22 In month of July it was 3.5 All the test was done from same lab in India as my husband works in muscat. Oman he got his CEA test done on 7th February 2021 which was 4.98 from an laboratory in muscat why is there a increase? his CT Scan reports was done in November which was normal plz advice