From the Division of Radiation Oncology, Duke University Medical Center, Durham, North Carolina (J.R.O., M.W.D): the Joint Center for Radiation Therapy, Harvard Medical School. Boston, Massachusetts (S.K.C.): the Radiation Therapy Department, Dartmouth-Hitchcock Medical Center, Hanover. New Hampshire (C.T.C.): the Department of Radiation Medicine, Massachusetts General Hospital. Harvard Medical School. Boston. Massachusetts (L.E.G.); the Division of Radiation Oncology, University of Utah Medical Center. Salt Lake City. Utah (F.A.G.); and the Division of Radiation Therapy. Stanford University School of Medicine, Stanford. California (D.S.K.).