WASHINGTON: People who have had kidney transplants face a big increase in risk for a variety of cancers, particularly those caused by a virus, according to a study published on Tuesday.

The researchers, writing in the Journal of the American Medical Association, tracked cancer incidence from 1982 to 2003 in nearly 29,000 Australians who got kidney transplants after serious kidney disease.

They excluded nonmelanoma skin cancer and cancers already known to lead to end-stage kidney disease, and found that the patients experienced an overall cancer risk nearly 3.3 times higher after getting a kidney transplant than before.

"We found that cancer incidence is markedly increased after kidney transplantation but is only slightly increased in the 5 years prior to and during dialysis," Claire Vajdic of the University of New South Wales in Sydney, lead author of the study, said by e-mail.

"After transplantation, the increase in risk affects a broader than previously appreciated range of cancers across a number of organ systems."

Vajdic said the findings do not challenge the life-saving value of kidney transplantation for people with end-stage renal disease, noting the risk of dying is four times higher in patients remaining on dialysis than in those who get a transplant.

The study found that the risk for 18 different kinds of cancer increased by at least three-fold, and 13 of these cancers are known or suspected to have a viral cause.

Five of these cancers, affecting the tongue, mouth, vulva, vagina and penis, are caused by the human papillomavirus, the study said, and there are indications the same virus is responsible in four of the others - cancers of the eye, salivary gland, esophagus and nasal cavity.

Immune system suppression, rather than the organ transplantation itself, is most likely responsible for the increase in cancer risk, Vajdic said.