[1] Univ British Columbia, Med, Vancouver, BC, Canada
[2] McMaster Univ, Clin Epidemiol & Biostat, Hamilton, ON, Canada
[3] Ontario Clin Oncol Grp, Clin Epidemiol & Biostat, Hamilton, ON, Canada
[4] George Washington Univ, Med, Pediat & Pharmacol & Physiol, Washington, DC USA
[5] Univ Maastricht, Care & Publich Hlth Res Inst, Epidemiol, Maastricht, Netherlands
[6] McMaster Univ, Oncol, Clin Epidemiol & Biostat, Hamilton, ON, Canada