1. From the Center for Biostatistics in AIDS Research, Department of Biostatistics, Harvard School of Public Health, and Sections of Hematology and Oncology, Department of Medicine, Boston Medical Center and Boston School of Medicine, Boston, MA; Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, NY; and Department of Medicine, Northwestern University Medical School and The Robert H. Lurie Comprehensive Cancer Center, Chicago, IL.