Organ transplantation is a life-saving measure for those with severe organ disease, yet it is not without risks, one of which is the subsequent development of cancer. Researchers from the National Cancer Institute studied this phenomenon in the Transplant Cancer Match Study.

The researchers collected information from the Scientific Registry of Transplant Recipients and 13 U.S. population-based cancer registries, generating data on cancer risk among 175,732 transplant recipients. This represented approximately 39.7% of the transplantations performed in the United States between 1987 and 2008. Sixty-one percent of the recipients were men; the median age was 47 years. More than half (58%) of organs transplanted were kidneys, followed by livers (21.5%), hearts (10%), and lungs (4%).

The number of malignancies diagnosed in the transplantation patients totaled 10,656-double the expected rate of cancer risk in the general population. The ratio of observed case to expected cases was higher for both infection-related cancers, such as non-Hodgkin's lymphoma and Kaposi's sarcoma, and cancers not related to infection, such as cancers of the lung, kidney, and thyroid. The researchers surmised that infection-related cancers stemmed from an impaired immune response that failed to eradicate cancer-causing viruses, whereas non-infection related cancers were possibly caused by inflammation, drug toxicity, or a preexisting condition.

Overall, non-Hodgkin's lymphoma and lung cancer were the most frequent cancers seen across all the transplant recipients. The incidence of both of these cancers was highest among lung transplant recipients. The researchers also noted many cancers arising from the site of the transplanted organ. For example, patients with liver and kidney transplants had the greatest risk of developing liver and kidney cancers, respectively. Some cancers were also more likely to present at a certain time after transplantation: in patients with liver transplants, 95% of liver cancers were detected within six months of surgery, and with non-Hodgkin's lymphoma, the first year after transplant carried the highest risk.-AK

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