Eating Pizza after cardio will nullify all the fat loss you might have experienced from the exericse. Most cardio sessions burn about 500 calories, and a couple of slices of pizza could easily have more then that amount.
However, you can make a low calorie, moderate carb, low fat, high protein pizza yourself. Just use whole wheat pita bread as the base, and put lots of chicken, veggies and a bit of low fat cheese on top. Thats what I do when I get a craving for pizza.