Last Updated: 2010-02-24 18:20:02 -0400 (Reuters Health)
NEW YORK (Reuters Health) - The risk for infection-related cancers in kidney transplant recipients falls dramatically when immunosuppression is stopped after graft failure, according to a study from Australia and New Zealand.
The finding holds promise for reducing risk of these cancers when solid organ transplants are successful, the researchers say.
In a population-based retrospective study of 8173 kidney recipients who had their primary transplant between 1982 and 2003, the researchers found that the risk for non-Hodgkin's lymphoma, lip cancer, Kaposi's sarcoma and melanoma returned to normal within weeks after immunosuppression was discontinued.
While it has long been known that rates of some cancers, especially those related to infection, are higher in immunosuppressed patients, this study is the first to examine what happens after the drugs are no longer administered, its authors say.
"Our study clearly shows that for these four cancer types, the effect of immune deficiency in increasing cancer risk is clearly and quickly reversible when immune deficiency stops," senior author Dr. Andrew E. Grulich told Reuters Health by email.
Dr. Grulich, an epidemiologist at the University of New South Wales, Sydney, Australia, added, "The speed of the reduction in cancer risk was very surprising. For non-Hodgkin's lymphoma, for example, this meant a 10-fold increase in risk disappeared within those first weeks after ceasing immune suppression."
"However, the effect was not general; we are only talking about a few specific types of cancer," he said.
As reported February 17 in BMJ Online First, standardized incidence ratios (SIRs) for cancer were significantly elevated during immunosuppression (when the graft was still functioning) but not after dialysis had resumed and immunosuppression was withdrawn. Specifically, the report indicates, SIRs during dialysis were 0.20 for non-Hodgkin's lymphoma, 0.04 for lip cancer, 0.16 for melanoma, and 0.25 for Kaposi's sarcoma.
However, similar reductions were not found for leukemia or for cancers of the lung, thyroid, kidney or urinary tract. In fact, thyroid cancer incidence remained significantly higher after transplant failure (SIR 6.77).
Because the reductions that did occur were so dramatic, Dr. Grulich speculates that minimizing immunosuppression in transplant recipients might also reduce their cancer risks. "If dose reduction is associated with reduced cancer risk, and this is possible without rejection of the transplanted organ, then this may be beneficial," he said, noting the need for additional studies.
BMJ 2010.
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