1 Center for Health Services Research in Primary Care, Durham VA Health Care System, Durham, NC, USA;; Division of General Internal Medicine, Duke University, Durham, NC, USA.
2 Department of Health Policy and Management, University of North Carolina, Chapel Hill, NC, USA.
3 Cooperative Studies Program Epidemiology Center, Durham VA Health Care System, Durham, NC, USA;; Division of Medical Oncology, Duke University, Durham, NC, USA.