@twin71, CEA is a protein marker that can be elevated in some cancers, like colorectal cancer, while creatinine is a waste product of muscle metabolism that indicates kidney function. Elevated creatinine levels and a low glomerular filtration rate (GFR) often indicate reduced kidney function, potentially suggesting kidney disease or kidney failure, but can also be caused by other factors.

Have you had a chance to talk to your doctor for further clarification? Is cancer treatment affecting your kidneys negatively?