** FILE ** Delaware Attorney General Beau Biden, right, takes a walk with his father,Vice President Joe Biden, to the Green Ridge Little Baseball Field in Scranton, Pa, July 4, 2012. Beau Biden is being evaluated at a cancer center in Texas, according to people with knowledge of his condition. (AP Photo/The Scranton Times-Tribune, Butch Comegys)

** FILE ** Delaware Attorney General Beau Biden, right, takes a walk with his father,Vice President Joe Biden, to the Green Ridge Little Baseball Field in Scranton, Pa, July 4, 2012. Beau Biden is being evaluated at a cancer center in Texas, according to people with knowledge of his condition. (AP Photo/The Scranton Times-Tribune, Butch Comegys)