1. Public Health Sciences Division, Fred Hutchinson Cancer Research Centre, 1100 Fairview Avenue North, Seattle, WA 98109, USA
2. Group Health Research Institute, Group Health Cooperative, 1730 Minor Avenue, Seattle, WA 98101, USA
3. Clinical Research Division, Fred Hutchinson Cancer Research Centre, 1100 Fairview Avenue North, Seattle, WA 98109, USA
4. Department of Medicine, University of Washington, WA, USA
5. John Hopkins University School of Medicine, 1650 Orleans Street, Baltimore, MD 21287, USA
6. Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
7. Public Health Sciences Division, Fred Hutchinson Cancer Research Centre, 1100 Fairview Avenue North, Seattle, WA 98109, USA.