My 88 Yr Old Mother Has A Pre Cancerous Tumor

My 88 yr old mother has a pre cancerous tumor in the tube leading out of the gall bladder. She has a temp stent and getting a permanent stent put in the tube to avoid blockages. She is currently seesawing between constipation and diarrhea every day. Is this a symptom of the gall bladder issue? What foods should she avoid?