Fill a 6-quart kettle three fourths full with salted water and bring to a boil for pasta. Cut crust from bread and, using large holes of a hand grater, grate enough bread to measure 2/3 cup. Finely chop separately capers and garlic.
Boil pasta until al dente.
While pasta is cooking, in a large heavy skillet cook garlic in oil over moderate heat, stirring, just until pale golden, about 2 minutes. Stir in capers, parsley, and bread crumbs and cook, stirring, until bread crumbs and garlic are golden, 1 to 2 minutes.
Drain pasta in a colander and transfer to a heated large bowl. Pour sauce over pasta and toss to combine.
