Researchers followed 354,000 patients for 20 to 34 years.
Numerous reports have documented transmission of solid and nonsolid malignancies and oncogenic viruses through organ transplantation, but studies of possible cancer transmission through blood transfusion have been inconclusive.
Researchers merged databases of all blood donations and transfusions in Sweden (from 1968 to 2002) and in Denmark (from 1982 to 2002); each transfused blood unit could be traced to its donor. That combined database was linked with national cancer registries in both countries. Donors who developed a new malignancy within 5 years after a blood donation were classified as “precancerous donors” who might have been harboring a subclinical malignancy at donation. The investigators then identified recipients who developed ne…