[1] Queens Univ, Kingston, ON, Canada
[2] Queens Univ, Div Canc Care & Epidemiol, Kingston, ON, Canada
[3] Princess Margaret Hosp, Toronto, ON M4X 1K9, Canada
[4] BC Canc Agcy, Vancouver, BC, Canada
[5] Trillium Hlth Partners, Mississauga Halton Cent West Reg Canc Program, Mississauga, ON, Canada
[6] Univ Toronto, Univ Hlth Network, Princess Margaret Hosp, Dept Radiat Oncol,Radiat Med Program, Toronto, ON, Canada
[7] Cross Canc Inst, Edmonton, AB T6G 1Z2, Canada
[8] Univ Toronto, Princess Margaret Hosp, Toronto, ON, Canada