Radiotherapy (RT) in rectal cancer increases postoperative morbidity. A suggested reason is RT-induced bone marrow depression resulting in impaired leucocyte counts. The ongoing Stockholm III Trial randomizes patients with operable rectal cancers to short-course RT with immediate surgery (SRT), short-course RT with surgery delayed for 4–8 weeks (SRT-delay) and long-course RT with surgery delayed for 4–8 weeks (LRT-delay). This study examined differences between the randomization arms regarding leucocyte response and postoperative complications.


Patients randomized in the Stockholm III Trial between October 1998 and November 2010 were included. Data were collected in a prospective register. Additional data were obtained by retrospective review of clinical records.


Of 657 randomized patients, 585 had data on leucocytes. The SRT arm had the highest proportion of postoperative complications (SRT, 52·5 per cent; SRT-delay, 39·4 per cent; LRT-delay, 41 per cent; P = 0·010). There was no association between low preoperative leucocyte count and postoperative complications (P = 0·238). Irrespective of randomization arm, patients with an impaired postoperative to preoperative leucocyte ratio had the highest rate of complications (low ratio, 56·6 per cent; intermediate ratio, 46·9 per cent; high ratio, 36·3 per cent; P = 0·010). The SRT arm had the highest proportion of low ratios (SRT, 48·9 per cent; SRT-delay, 22·8 per cent; LRT-delay, 22 per cent; P < 0·001).


An impaired postoperative leucocyte response is associated with postoperative complications. The highest risk is with immediate surgery following short-course radiotherapy. Registration number: NCT 00904813 (