1. Department of Medicine, Stanford University School of Medicine, Stanford, 94305 CA 94305, USA
2. Division of Oncology, Department of Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
3. Division of Oncology, VA Palo Alto Healthcare System, Palo Alto, CA 94304, USA
4. Center for Health Policy/Primary Care Outcomes Research, Department of Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA