NEW YORK (Reuters Health) – Solid organ transplant recipients have a risk of cutaneous squamous cell carcinoma (SCC) that’s more than 100 times higher than average, according to a Swedish population study.
The risk of any de novo cancer was greatest for heart and lung recipients, the study also found.
“The overall and site-specific findings are consistent with previous estimates of cancer risk after transplantation,” said Dr. Claire Vajdic, a cancer epidemiologist at the University of New South Wales in Australia who was not involved in the study.
But, she told Reuters Health by email, “Unlike nearly all other countries, they were able to identify incident SCCs in their solid organ transplant recipients…They were able to quantify, for the first time using sound population-based methods, the risk of subsequent SCC.”
The investigators, led by Britta Krynitz at the Karolinska University in Stockholm, used Swedish national patient registries to identify 10,476 organ transplant recipients between 1970-2008.
Kidney transplants were by far the most common (N= 7,952), followed by liver (n=1,221), heart (n=557), lung (n=438), and multiorgan transplants
Heart and lung transplant recipients had the highest incidence of de novo cancer. The risks in this population were 198 times higher than in the general population for SCC and 3.3 times higher for all other cancers.
Kidney recipients were 121 times more likely to develop SCC and 2.3 times more likely to develop any other cancer, compared to the average person in the general population.
Overall, transplant recipients developed all cancers other than SCC at 2.4 times the rate in the general population, and SCC at 121 times the average rate.
The investigators also stratified the risk of cancer by post-transplant interval. For all cancers other than SCC, the rate remained steady at 2.3 to 2.4 as the interval lengthened from four years to 20 years. For SCC, however, the increased risk went from 50-fold during the first four years post-transplant to a 213-fold increase at greater than 20 years.
The increase was driven by a small group of patients who developed new SCCs at an increasing rate over time, according to the authors.
The researchers say that while the connection between transplant and later skin cancer is likely due to the immunosuppression drugs, the exact pathway isn’t clear. Some of these cancers might be viral — viruses have been isolated in some skin cancers in transplant patients — but it’s also clear that sun damage repair is less efficient in immunosuppressed individuals.
“The role of virus is not quite clear, but clearly the sun damage itself and ultraviolet change in the cells is what causes skin cancer and immunosuppressed patients can’t fight those changes as well,” said Dr. Elizabeth Billingsley at Penn State University, who is president of the International Transplant Skin Cancer Collaborative.
Dr. Billingsley, who wasn’t involved in the Swedish study, said too few physicians and patients are aware of how severe the problem can be.
“I think people kind of know about it — they know that immunosuppressed people are more prone to develop problems, including skin cancer. But I don’t think most people are aware how devastating and life-threatening these skin cancers can become,” she said. “This kind of study is powerful and can help spread that message better.”
She said increased screening — as often as once every three months for high-risk transplant patients — can help prevent serious skin cancers.
Full results of the study were published online August 7 in the International Journal of Cancer. Lead author Dr. Britta Krynitz did not respond to a request for comment on the study’s results.
Int J Cancer 2012.