Preheat oven to 350 degrees F (175 degrees C). Prepare a casserole dish with cooking spray.
Bring a large pot of lightly salted water to a boil. Cook elbow macaroni in the boiling water until cooked through but firm to the bite, 8 minutes; drain.
Stir cooked elbow macaroni, cream of chicken soup, Cheddar cheese, tuna packed in water, milk, and butter together in a large bowl; pour into prepared baking dish.
Sprinkle bread crumbs over macaroni mixture.
Bake in preheated oven until golden brown on top, 35 to 40 minutes.
