Blood transfusion and colorectal cancer
Ross, William Beattie
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Blood transfusion enhances graft survival in renal transplant recipients. The mechanisms involved are unclear, but suppression of cell- mediated immunity plays a central role. This has led to the suggestion that blood transfusion may cause immunosuppression in cancer patients and this could have a detrimental effect on their survival.A retrospective study of 314 patients who had bowel resection for colorectal cancer was performed. Transfused patients had a poorer five year survival rate, but this was probably related to the fact that over 90% of patients with low rectal carcinoma who had an abdomino -perineal resection were transfused. Subsequently, the patients who had abdomino -perineal resections were excluded to limit analysis to the 159 patients who had abdominal resections. The 5 -year survival was 34% in those transfused, compared with 47% in those who were not, but this was not a significant difference.In the experimental research the aim was to establish a model of colonic cancer in which blood transfusion caused immunosuppression. Analysis of peripheral T cell subsets has been used to assess suppression of cell -mediated immunity. Subsets were counted using flow cytometry and monoclonal antibodies to T lymphocytes. There were no significant changes in subsets after transfusion with blood in normal rats. However, in older rats, transfusion with blood caused a significant increase in suppressor cells.Blood transfusion enhances growth of transplanted tumours in animals and recent evidence implicated macrophage prostaglandin E2 as a mediator of transfusion- mediated immunosuppression. The next objective was to study the influence of blood transfusion on the course of colonic carcinogeneis and the possible abrogating effects of indomethacin. This study confirmed that blood transfusion enhanced dimethylhydrazine carcinogenesis and suggested that treated rats with indomethacin, a prostaglandin synthetase inhibitor, at the time of transfusion may abrogate this effect.Using a rat peritoneal macrophage model, it was shown that blood transfusion increased prostaglandin E2 production by these cells in vitro. Allogeneic serum caused the greatest increase, while transfusion with stored allogeneic and syngeneic blood both caused an increase in prostaglandin E2 production. This suggests immunomodulation by factors associated with storage of blood in addition to a genetic effect.In conclusion, there is evidence that blood transfusion is associated with reduced survival of colorectal cancer patients, but this may be due to more advanced malignancy in transfused patients. Blood transfusion enhances colonic carcinogenesis in rats and this may be abrogated by indomethacin. Blood transfusion increased prostaglandin E2 production by macrophages and this supports the theory that transfusion associated immunosuppression may be mediated by this effect.