[1] Univ Groningen Hosp, Dept Internal Med, NL-9713 EZ Groningen, Netherlands
[2] Univ Groningen Hosp, Dept Surg, NL-9713 EZ Groningen, Netherlands
[3] Leiden Univ, Dept Med Stat, Med Ctr, NL-2300 RA Leiden, Netherlands
[4] Comprehens Canc Ctr N Netherlands, Groningen, Netherlands