How long can an Alzheimer's patient live with cancer, and is treatment worth while?

Hello all... been a while since my last post. Mom (late severe AD) is in ICU, had part of colon removed, one ovary and a tumor the size of a grapefruit. We just got the pathology report that says stage 3c colon cancer. Also the cancer has spread to 7 lymphnodes . My question is... what is the survival rate with AD patients and this type of cancer... anyone had experience with this... do I try to do treatments with the advance AD???? thanks in advance.