Kidney Transplants Boost Cancer Risk
Immunosuppressive drugs can triple odds for many malignancies, study finds
WEDNESDAY, Dec. 20, 2006 (HealthDay News) -- Some patients have a threefold increased risk of developing a variety of cancers after receiving a kidney transplant, Australian researchers report.
Drugs used to prevent rejection of the new kidney by suppressing the body's immune system may be to blame for a bump in risk for nonmelanoma skin cancer, non-Hodgkin lymphoma and the rare skin malignancy known as Kaposi's sarcoma, researchers report in the Dec. 20 issue of the Journal of the American Medical Association.
"We found that the incidence of cancer in many organs was markedly increased after kidney transplantation," said lead author Claire M. Vajdic, a research fellow at the University of New South Wales, Sydney. "The risk was 300 percent higher than in the general population," she said.
Most of the cancers that these patients developed have a known or suspected viral origin, Vajdic noted. "Our findings are strongly suggestive for the role of the immune system in the prevention of cancers in normal healthy human beings," she said.
In the study, Vajdic and colleagues compared the incidence of cancer in nearly 29,000 patients with end-stage kidney disease who received kidney transplants. The researchers collected data from the five years before the transplant, during dialysis and after transplantation.
Vajdic's team consulted the Australia and New Zealand Dialysis and Transplant Registry and the Australian National Cancer Statistics Clearing House to identify cancers occurring from 1982-2003. They then compared those statistics with the number of cancers seen among transplant patients.
The group found that, after transplant, the overall incidence of cancer rose 3.27 times (this statistic excluded nonmelanoma skin cancer and cancers known to frequently cause end-stage kidney disease).
Malignancies rose significantly at 25 body sites after transplant, and the risk exceeded threefold at 18 of these sites, the researchers report
These cancers included melanoma, Kaposi's sarcoma, non-Hodgkin's lymphoma, Hodgkin's disease, leukemia and cancers of the lip, tongue, mouth, salivary gland, esophagus, stomach, colon, anus, liver, gallbladder, lung, connective and other soft tissue, vulva, cervix, penis, eye and thyroid. There was also a significant increase in nasal cavity and vaginal cancers.
The probable culprit: The immunosuppressive drugs transplant patients take lower their ability to fight off infections that can trigger malignancy, Vajdic said. "We believe the increased incidence of infection leads to the infection that results in cancer," she said.
Vajdic noted that there is probably an even greater increased risk of cancer among patients who receive heart and heart-lung transplants. "These people receive even more powerful immune suppression," she noted.
One expert believes patients need to be aware of the risks associated with immunosuppressants.
"This is a fascinating paper," said Dr. Amy Friedman, an associate professor of surgery at Yale University School of Medicine. "It, for the first time, gives us a statistical demonstration of what we see clinically but could not prove," she said.
The study drives home the point that using immunosuppressive drugs is a major decision impacting patient health, Friedman said. "That is extremely relevant today because you are seeing new types of transplants being performed," she said.
"We now have transplants that are called quality-of-life transplants, such as a hand transplant and a face transplant," Friedman said. "It is really critical that when those transplants are done, that the patients are fully educated about risks of immunosuppression, such as cancers," she said.
Friedman noted that these medications today affect the entire immune system. There is hope that, in the future, these medications will be more selective and target only the part of the system responsible for rejecting the transplant. "That's our objective, but we are not there yet," she said.
There's more on kidney transplant at the American Society of Transplantation.