Patients who receive a kidney transplant are at an increased risk of developing cancer, especially skin cancer, and Irish researchers believe they have discovered why.

According to their findings, this increased risk is related to anti-rejection medications.

Researchers at the Royal College of Surgeons in Ireland (RCSI) analysed the pattern of skin cancer rates in kidney transplant patients and found that the risk of cancer falls when a transplant fails and the patient returns to dialysis.

This risk increases again when the patient receives another transplant, although the rate of skin cancer is still higher in patients with failed transplants than pre-transplant patients on dialysis.

Due to this pattern, the researchers believe that the risk of cancer is related to the stopping and starting of anti-rejection medications.

The RCSI study analysed the rates of cancer in over 3,800 kidney transplant recipients, all of whom had undergone one, two or three transplants.

It found that during the patient's first kidney transplant, the rate of skin cancer rose 15 times higher than before the procedure. That skin cancer rate fell by half when the transplant failed and the patient returned to dialysis. However, the rate was still seven times higher than the pre-transplant patient's rate.

When the patient received a second transplant, the rate of skin cancer rose again to 12 times more than the pre-transplant rate.

"In recipients of multiple kidney transplants, the incidence of non-melanoma skin cancer fell during periods defined by transplant failure, but there was still an elevated risk. The incidence of cancer overall highlights the need for continued cancer surveillance during graft failure," commented the study's lead author, Dr Donal Sexton, of Beaumont Hospital and the RCSI.

The research was a collaboration between the National Cancer Registry Ireland and the National Kidney Transplant Service in Beaumont Hospital. Details of the findings are published in the journal, JAMA Dermatology.