Organ Transplant Recipients Are at Increased Risk for a Range of Cancers
Patients who have received a solid organ transplant, such as a kidney, lung, or heart transplant, are twice as likely to develop cancer as the general population, and the risk extends to a broad range of cancers, according to research published November 1 in JAMA.
Doctors have known since the early days of organ transplantation that cancer is a possible complication of this often life-saving procedure. The new study gives researchers the first overview of cancer risk patterns in a large population of solid organ transplant recipients in the United States, including risk patterns for less common cancers.
"The risk is increased for quite a broad group of cancers," said lead investigator Dr. Eric Engels of NCI's Division of Cancer Epidemiology and Genetics (DCEG). "By clarifying the spectrum of these cancers, the results of this study encourage us to think about why that might be."
He and his colleagues found higher risks for 32 types of cancer among a group of nearly 176,000 transplant recipients in the Transplant Cancer Match Study. Although the risks varied depending on the type of cancer, the overall risk estimate was in line with previous studies.
Much of the increased risk of cancer among organ transplant recipients has been attributed to the medications these patients use to prevent the immune system from rejecting a donor's organ. Suppressing the immune system raises the risk for certain cancers, particularly cancers caused by an infectious agent, such as a virus.
In the current study, non-Hodgkin lymphoma, which can be caused by the Epstein-Barr virus, was the most common cancer, and the risk was greatly increased in organ transplant patients compared with the general population. The researchers also found an increased risk of cancers with no established links to infection, including melanoma, lip cancer, and thyroid cancer.
This study underscores the important role of the immune system in the prevention of cancer, noted Dr. Claire Vajdic of the University of New South Wales, Australia, whose research involves organ transplantation and cancer but who was not involved in the study.
"The findings very clearly demonstrate that this population has an increased risk for a remarkably wide range of solid and hematological cancers," she wrote in an e-mail message. "Strategies for preventing cancer in this high-risk population are of paramount importance."
A better understanding of cancer risk in transplant recipients would help clarify the role of the immune system, infections, and other factors in the development of malignancies, the study authors noted. This could also reveal ways to improve the safety of organ transplantation, they added.
Dr. Engels and his colleagues analyzed data on solid organ transplant recipients from the U.S. Scientific Registry of Transplant Recipients (1987–2008) and data from 13 state and regional cancer registries. Most previous studies were not large enough to develop risk profiles for less common cancers.
"We are very excited about this study," said Dr. James Bowman, medical director of the Division of Transplantation within the Health Resources and Services Administration. "Until now, we have not had a way to attach reliable numbers to these less common cancers."
Eventually, Dr. Bowman added, information about cancer risks could help primary care physicians "remain alert" to the potential cancer risks for their patients who have received organ transplants.
The study found high rates of some common cancers within the first 6 months of transplantation, Dr. Vajdic noted. But she cautioned that these rates may include cancers that were present but undetected in organ recipients at the time of transplantation, rather than cancers that resulted from the procedure and immune system suppression.
—Dr. Eric Engels
News reports have occasionally described cases where a patient may have developed cancer after receiving an organ from a donor who had an undiagnosed tumor. But in the current study, Dr. Engels said, this type of transmission probably accounted for no more than a very small fraction of cases, if any.
An unexplained finding from the study was an increased risk of kidney cancer in patients who received organs other than a kidney. Investigators in the United Kingdom recently reported a similar result.
"The explanation for this is not known, but our results may lead researchers to ask new questions about why cancers develop in transplant recipients," said Dr. Engels. "It's not just suppression of the immune system that is increasing the risk of cancer; other factors are likely to be involved."
More than four decades have passed since Dr. Israel Penn first reported cancers occurring in transplant recipients. A pioneer in organ transplantation, he started a national registry that spurred research on cancer risks in transplant recipients and laid the groundwork for the current study.
"Organ transplantation is one of the miracles of modern medicine, and it represents a new lease on life for patients with organ failure," said Dr. Engels. "We will continue to do research to learn how to minimize the burden of cancer in these patients."