1. Department of Medicine and Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6021; University of Pennsylvania Cancer Center, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6021; Leonard Davis Institute of Health Eonomics, University of Pennsylvania, Philadelphia, PA 19104
2. Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA 19104; University of Pennsylvania Cancer Center, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6021
3. Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6021; University of Pennsylvania Cancer Center, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6021
4. Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6021