Impaired postoperative leucocyte counts after preoperative radiotherapy for rectal cancer in the Stockholm III Trial

Background: 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. Methods: 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. Results: 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). Conclusion: 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 (http://www.clinicaltrials.gov). Presented in part to a meeting of the European Society of Coloproctology, Vienna, Austria, September 2012; published in abstract form as Colorectal Dis 2012;14(Suppl 2):8