[1] Univ Toronto, St Michaels Hosp, Div Hematol Oncol, Toronto, ON, Canada
[2] McGill Univ, Dept Epidemiol Biostat & Occupat Hlth, Montreal, PQ, Canada
[3] Univ Toronto, Fac Med, Toronto, ON, Canada
[4] St Michaels Hosp, Toronto, ON, Canada
[5] Univ Toronto, Dept Surg, Toronto, ON, Canada