[1] Univ Hosp Leuven, Louvain, Belgium
[2] Norwegian Radium Hosp, Oslo, Norway
[3] Inst Med Informat, Oslo, Norway
[4] Univ British Columbia, Vancouver, BC V5Z 1M9, Canada
[5] Gartnavel Royal Hosp, Glasgow, Lanark, Scotland
[6] Beatson W Scotland Canc Ctr, Glasgow, Lanark, Scotland
[7] Hosp Univ San Carlos, Madrid, Spain