1. Department of Surgical and Perioperative Sciences , Surgery, , SE-901 85, Umeå , Sweden
2. Umeå University , Surgery, , SE-901 85, Umeå , Sweden
3. Department of Radiation Sciences, Umeå University , Umeå, SE-901 85 , Sweden
4. Department of Surgery, Sunderby Hospital , SE-971 80, Luleå , Sweden