Kidney transplants can save lives. They can also increase the risk of developing a variety of cancers, according to Australian researchers who report a risk 300 percent higher than in the general population.

Most cancers developed in kidney transplant patients have a known or suspected viral origin, suggesting the weakened immune systems in these patients limit protection against cancer.

"The immunosuppressive drugs transplant patients take lower their ability to fight off infections that can trigger malignancy", the lead researcher said. "We believe the increased incidence of infection leads to the infection that results in cancer." She also notes there is probably an even greater risk of cancer among heart and lung transplant patients because these patients receive more powerful immunosuppressive drugs.

Researchers gathered their findings by comparing the incidence of cancer in 29,000 patients with end-stage kidney disease who received kidney transplants. Data was collected beginning five years prior to transplantation, during dialysis, and after transplantation. Researchers then consulted an Australian registry to identify cancers occurring between the years of 1982-2003. They compared the statistics with the number of cancers seen among transplant patients.

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 an increase in nasal cavity and vaginal cancers.

This study has important implications for future immosuppression. Patients should give considerable thought to quality-of-life transplants -- such as face transplants and hand transplants -- and should carefully weigh the risks of weakened immunity. On a brighter note, this study might help prompt research on medication that can selectively target the part of the body responsible for rejecting a transplant. Because right now, medications affect the entire immune system -- and this is what makes patients more prone to developing cancer.