The risk of acquiring autologous stem cell graft
By Wayne Channon
According to recent research, this risk is "Fewer than 1 in 2500". For a child in whom there is a direct family history of Sickle cell disease, Fanconi or Diamond-Blackfan anaemia and some inherited Leukaemias, the risk of a sibling or child requiring a stem cell transplant may be much higher depending on a number of factors. For a healthy family without a dominantly inherited malignancy or condition of this type the risk quoted may in fact be far less than 1 in 20,000 as there have only been 4 or 5 documented cases of autologous cord blood stem cell transplants worldwide to date.
The issue of autologous use is one of intense debate. Autologous stem cell transplantation is well established and used for a variety of haematological and solid tumours. I would draw reference to Gratwohl et al. (2001) who summarised the Haematopoietic stem cell transplantation activity in Europe in 1999. Of 18,720 first transplants 69% (12,841) were autologous (this figure includes 6,289 transplants for leukaemias, 30% autologous; 8,219 transplants for lymphomas, 92% autologous; 3,302 transplants for solid tumours, 99% autologous). This activity has increased substantially over the last few years. The debate is not whether there is a role for autologous progenitor cell transplantation but will cord blood stem cells provide the source of these cells for autologous use in the future. At Cells 4 Life, we believe that as the cohort of patients who have stored cord blood worldwide is followed autologous use of this resource will replace conventional peripheral blood progenitor cell mobilisation procedures and therapies currently available. Unfortunately the cord blood storage programmes are not yet old enough to be releasing samples for this use.
There is another debate with regard to autologous use, which is that for selected blood malignancies the genetic defect is pre-programmed and which would prohibit autologous use as a therapy option. The review by Greaves (2002) referred to a study where 1% of 600 blood samples were positive for the TEL-AML1 fusion gene (a common leukaemogenic marker). This incidence is approximately 100 fold the cumulative risk rate of ALL (with TEL-AML1 gene) and clearly indicates that the conversion of the pre-leukaemic clone to overt disease is low, suggesting multi hits are required for evolution of the disease. The concept of a multi-hit mutative process may mean that in fact there is a role for cord blood stem cells collected at birth, as the subsequent leukaemic changes would not occur until some time after birth
The use of autologous cord blood is only in part the issue as many families choose to privately store their child's cord blood for potential therapeutic applications for siblings. Examples of this include patients in whom a sibling is awaiting cardiac transplantation where there may be a possible use of the sample as a cellular cardiomyoplasty at some point in the next 5 years. Other examples include diabetic families who are making an informed choice to store their child's cord blood based on the currently available research evidence for gene therapy based stem cell therapies for diabetes that have shown promising results.
About the Author
Wayne Channon, Director of Cells4Life Ltd, a Stem cell and cord blood storage expert.
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