Abstract
BACKGROUND: Blood transfusions are common in older adults and also may modulate the immune system. However, the impact of transfusion on cancer risk in the elderly has not been studied. STUDY DESIGN AND METHODS: Cancer risk after blood transfusion was evaluated in a US population-based case-control study using 552,951 elderly cases identified from cancer registries and 100,000 frequency-matched controls. Transfusions received 0 to 12, 13 to 30, and 31 to 48 months before cancer diagnosis or selection date were identified using Medicare claims. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using logistic regression models. A Bonferroni correction adjusted for multiple testing. RESULTS: Transfusions received 0 to 12 months before cancer diagnosis and/or selection were associated with significantly elevated risk of cancer overall (OR,2.05; 95% CI, 1.95-2.16) and cancer of the stomach; cancer of the colon; cancer of the liver, kidney, renal pelvis, and/or ureter; lymphoma; myeloma; and leukemia. No significant associations for cancer overall were observed for the two earlier intervals. No site was associated with transfusions received 13 to 30 or 31 to 48 months before diagnosis and/or selection. Nonetheless, overall cancer risk increased with the number of transfused periods (p-trend<0.0001). CONCLUSION: Risk of overall cancer and specific sites was elevated 0 to 12 months after blood transfusion and associated with multiple transfusions, possibly due to reverse causation, that is, incipient cancers or cancer precursors causing anemia.