Bring a large pot of salted water to a boil. Add the spaghetti and cook according to package directions for al dente; drain, reserving 2 tablespoons cooking liquid.
Meanwhile, cook the pancetta in a large skillet over medium heat until crispy, about 4 minutes. Add the garlic, pecans, and red pepper flakes and cook 1 minute. Add the broth and wine and cook until reduced by half, about 2 minutes. Stir in the butter and cheese.
Add the cooked pasta to the skillet and toss to coat. Stir the reserved pasta water into the sauce if needed to thin out the sauce slightly. Stir in the radicchio and parsley.
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