Dr. Hollenbeak

Hershey, Pa. — An increased risk of developing a variety of cancers has long been associated with kidney transplants, but a direct correlation has never been made between renal transplants and the development of melanoma — until now.

A retrospective study done by medical economists and dermatologists from Penn State College of Medicine here, finds that kidney transplant patients are 3.6 times more likely to develop the deadliest form of skin cancer than are people in the general population — and the story is even worse for men as they get older.

National registry

The researchers used the resources of the United Networks for Organ Sharing Registry that contains all the clinical information about the patients and their transplants. As a national registry, it combines transplant data with Medicare payment data.

Skin, breast cancer link

Health economist Christopher S. Hollenbeak, Ph.D., assistant professor of surgery and health evaluation sciences at Penn State College of Medicine, says the registry makes kidney transplant patients unique in that respect.

"Because end-stage renal disease was included in the eligibility criteria for Medicare when Congress was first developing the program, the vast majority of transplant patients are covered by Medicare — so their payment data as well as all of the really important clinical information is included. It's not often you get data sets that combine all of those elements," he says.

The registry enabled the researchers to compare melanoma incidence rates of nearly 90,000 kidney transplant patients to the general population. The medical records show that renal transplant recipients develop melanoma about 3.6 times more often than did the general population.

Dr. Hollenbeak tells Dermatology Times that the reason for the increased risk of melanoma is probably primarily related to the same factors that show an increased risk of a variety of cancers in transplant patients.

"The usual hypothesis is that transplant patients are on immunosuppressants for the rest of their lives. In the normal patient, a functional immune system goes a long way toward protecting one from cancer. So, if you suppress the immune system you would naturally expect the risk to increase."

Unexpected, unexplained

But the statistics revealed some unexpected, and some unexplained, results.

For men, the risk of developing melanoma increases with age — almost exponentially. After the age of 65, male kidney recipients show about a five and a half times greater risk of melanoma than did non-transplant patients. For women, the risk increases until they reach the 55 to 64 age-range, then it levels off.

"We're really not sure why that happens, although one potential explanation could be that men are more likely to hold outdoor jobs than women."

One statistic that is not clear in the registry is the degree of immunosuppression that occurs in individual patients. Researchers did look at whether patients had any episodes of acute rejection because patients suffering acute rejection typically have higher levels of immuno suppression in order to control the possibility of rejection.

Dr. Hollenbeak says, "You would think that if you had a higher degree of immuno suppression, you should probably also have more risk of melanoma. We found that the risk is increased for patients with acute rejections, but the numbers were not statistically significant. That could be due, at least partially, to the sample size. Although the numbers were not great enough to be significant, they do move in the right direction."

Interestingly, although the incidence of melanoma among blacks is generally very low, among black kidney transplant patients, the risk of melanoma is much, much higher.

"The odds of developing melanoma if you were black and had a kidney transplant are 17 times higher than in blacks in the general population," Dr. Hollenbeak says.