Mix cake mix according to the directions on the box, omitting water, and adding the pumpkin, cinnamon and bananas. Spoon into one sprayed 9-inch loaf pan or 4 5-inch loaf pans. Bake at 375 degrees F for 50 minutes for 9-inch loaf or 30 minutes for 5-inch loaf or until a toothpick inserted in the center comes out clean (cover with foil the last 10 minutes if loaves get too brown).
In a medium bowl combine the cream cheese and butter with an electric mixer until creamy. Stir in the vanilla, and then gradually mix in the powdered sugar. Let the pumpkin bread cool completely and then frost. Chill to store.