Bring 6 quarts water and 2 teaspoons salt to a boil in a large stockpot. Stir in pasta; partially cover, and return to a boil, stirring frequently. Cook 8 minutes or until pasta is almost al dente, stirring occasionally. Drain.
While pasta cooks, heat olive oil in a Dutch oven over medium-high heat. Remove casing from the sausage. Add sausage to Dutch oven; cook 2 minutes or until lightly browned, stirring to crumble. Add leek; cook 2 minutes or until leek is soft, stirring frequently. Add cabbage; cook 2 minutes or until cabbage wilts, stirring frequently. Add remaining 1/2 teaspoon salt, broth, and pepper; bring to a boil. Reduce heat, and simmer 15 minutes or until vegetables are very tender.
Add pasta to Dutch oven, tossing well to coat; bring to a boil. Reduce heat, and cook 1 minute, stirring constantly, or until pasta is al dente. Remove from heat; stir in cheese. Serve immediately.