People who've received a kidney, liver, lung or heart transplant may have double the risk of developing cancer compared with the general population, but the risk is still low overall, a new U.S. study suggests.
Organ transplant recipients are thought to have a higher risk because their immune systems are suppressed by medications to prevent the organs from being rejected and they are more prone to cancers related to viruses such as hepatitis B or C viruses that cause some liver cancers.
"In this large, population-based study of US transplant recipients, we observed a two-fold overall increased risk of cancer," the study's authors wrote in Tuesday’s issue of the Journal of the American Medical Association.
The researchers estimated the risk of developing cancer after a transplant is 0.7 per cent.
"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 malignancy, and could identify opportunities to improve transplant safety," concluded Dr. Eric Engels of the National Cancer Institute in Rockville, Md., and his colleagues.
Other contributing factors for some cancers may include other effects of chronic immune disturbance or inflammation, underlying medical conditions, or medication toxicity.
The researchers analyzed data on organ transplant recipients and 13 state and regional cancer registries to determine cancer risk in transplant recipients compared with the general population.
The most common transplanted organs in the study were:
The study included data on nearly 176,000 solid organs transplanted between 1987 and 2008.
Transplant recipients were linked to 10,656 cancer diagnoses during follow-up. The risk was higher for 32 different types of the disease.
The potential reasons for increased cancer risk varied by transplant type. For example, non-Hodgkin lymphoma risk was especially high among lung recipients, possibly as a result of the intensity of immunosuppression or the large amount of tissue they received, the researchers said.
Two cancers showed decreases, breast and prostate. The study's authors acknowledged those decreases could arise from screening before transplant that led to the removal of those cancers. Higher medical surveillance could also be contributing.
This research was funded in part by the U.S. National Cancer Institute.