Melissa Gilbert witnessed her TV dad, Michael Landon, fight a debilitating disease that ultimately took his life. At age 54, the actor who played patriarch Charles Ingalls in "Little House on the Prairie" was diagnosed with pancreatic cancer. He died three months after publicly announcing his diagnosis in 1991. "It is really a brutal and pernicious disease," Gilbert told People magazine. "To me, it felt like a tornado. You have no warning. It’s just there and the survival rate is virtually nil."