Recipients of kidney transplants may have a three-fold increase in risk for a large number of cancers, especially those commonly associated with viral infection, according to an article in the December 20 issue of Journal of the American Medical Association.

Immune suppression after organ transplantation is associated with a markedly increased risk of nonmelanoma skin cancer, non-Hodgkin lymphoma, and Kaposi sarcoma. Whether other cancers occur at increased rates is uncertain because there have been few long-term population-based studies, according to background information in the article.

Claire M. Vajdic, PhD, of the University of New South Wales, Sydney, Australia, and colleagues compared the incidence of cancer in 28,855 patients with end-stage kidney disease who received a kidney transplant. Data were collected for three separate time periods: the five years before transplantation, during dialysis, and after transplantation. New cancers (1982-2003) were determined by record linkage between the Australia and New Zealand Dialysis and Transplant Registry and the Australian National Cancer Statistics Clearing House.

The researchers found that the overall incidence of cancer, excluding nonmelanoma skin cancer and those cancers known to frequently cause end-stage kidney disease, was markedly increased (3.27 times) after transplantation. In contrast, cancer incidence was only slightly increased (1.35 times) during dialysis and before transplantation (1.16 times). After transplantation, cancer occurred at significantly increased incidence at 25 sites, and risk exceeded three-fold at 18 of these sites.

"Although the incidence of some cancers was increased during dialysis, and the incidence of a few was increased before kidney transplantation, the magnitude and breadth of the increased risk after transplantation suggests that immune suppression causes a substantial and broad-ranging increase in cancer risk," the authors wrote.

"After kidney transplantation, a wide variety of cancers across a number of organ systems occur with substantially increased incidence. Most, but not all, of these cancers are those with known or suspected viral causes. In contrast, cancer incidence was only slightly increased before kidney transplantation. Our findings point to an important role of the interaction between common viral infections and the immune system in the etiology [cause] of cancers at a broad range of sites," the researchers concluded.