People who receive stem cell transplants for diseases such as leukaemia appear to face a higher risk of developing secondary cancers, especially if the cells come from a female donor, according to a preliminary study.
The study was carried out by Canadian scientists who caution that future stem cell treatments for ailments such as spinal cord injury and heart failure might also carry a cancer risk, the New Scientist reported on Monday on its website.
The scientists at the British Columbia Cancer Agency in Canada in the study reviewed the medical records of more than 900 adult patients who had received haematopoietic stem cell transplants, also known as bone marrow transplants, in the past two decades, with the vast majority of these transplant recipients suffering from leukaemia, the report said.
Of the patients included in the study, 28 developed secondary tumors such as skin, lung or breast cancer within 10 years of receiving the stem cell transplant, according to the scientists.
After having excluded some of these cancers from their analysis due to incomplete reporting, the scientists found that the remaining patients faced a 2.3% risk of cancer over the course of 10 years, nearly twice the risk in the general population.
The analysis also revealed that patients who received stem cell transplants from female donors had an even higher risk of developing a secondary tumor with their risk of developing cancer over the course of 10 years at 4.6%, while patients given stem cells from a male donor had a 1.8% risk.
Men who received stem cells from female donors had more than twice the risk of developing cancer compared with women who received the same, according to the study which is the first study to demonstrate that stem cells from women carry a greater cancer risk than those from men.
The cells from female donors, many of whom have had children, might differ somehow, lead scientist Donna Forrest said, adding their pregnancies might have made their cells more likely to be disruptive when transplanted into recipients.
This in turn might have caused chronic inflammation in the patients, putting them at greater risk for cancer, she speculated.
The findings are preliminary and that the analysis did not control for confounding factors such as whether a patient smoked or maintained a healthy body weight and it therefore remains unclear exactly how much the stem cell transplants contributed to the risk of second cancers, she said.
Experts also caution that the drugs given following such transplants are known to put patients at greater risk of these secondary tumors.
However, experts point out that the study is far from conclusive and more work needs to be done to confirm a link between stem cell transplants and tumors.