Pre-emptive stem cell banking in high-risk individuals: Should Japan’s nuclear workers have their stem cells stored?

by David Kent

A few weeks back, The Guardian reported on a proposal by Japanese doctors and scientists that would see the blood cells of Japanese nuclear clean-up workers banked as a precaution against possible exposure to radiation during the clean-up of the Fukishima power plant. The idea would be to harvest and store their blood cells^[1] and, should the worker require a transplant in the future due to the development of a blood cancer or bone marrow failure, to then re-infuse the patient’s own blood cells from the pre-exposure state. This would avoid complications like graft-versus-host disease and finding a donor match.  Furthermore, many businesses and hospitals have pledged their help both inside Japan and internationally.

Sounds pretty amazing right? 

Well yes, but there has been substantial dissent, and this dissent has moved the Japanese government to not support the initiative, despite the support of the Japan Society for Hematopoietic Cell Transplantation. The debate of how useful these transplants would be is well-summarised by Alice Park and appears to boil down to two main arguments: 1) Blood cells are only one tissue type that bear the effects of radiation and blood cell therapies would not help with gastrointestinal or lung damage; and 2) Workers may have an extra (unwarranted) sense of security and take unnecessary risks.

In response to this, the medical science team released a follow-up letter explaining their proposal, which appeared in The Lancet this week. In it, they cite the Chernobyl and Tokaimura disasters, where a combined 11 patients required allogeneic transplantation. This, combined with the expected years of work that it will take to fully shut down the Fukishima site make a compelling argument to embark on projects that will maximize the safety of the workers.

Furthermore, irrespective of whether or not these cells are used for transplants into workers, they represent a potentially valuable clinical resource. With appropriate consent, these workers could provide pre-exposure and post-exposure samples for whole genome analysis to determine the effects on genomic DNA (if any) of sending workers into such radiation intense areas and allow more informed risk assessment to be undertaken in the future. This will not be the last nuclear disaster that occurs in our world and knowing more rather than less about the effects of cleaning up seems reasonable.

Finally, we are left with a practical question to consider in Canada: Is the idea of banking cells from higher risk individuals a good one? A large scale roll out of such a procedure would be remarkably expensive and likely not beneficial for the vast majority of Canadians, including those that work in areas of higher exposure where “studies to date have not been able to show any excess cancers or other diseases in people chronically exposed to radiation at doses lower than about 100 mSv” which is the Canadian Nuclear Safety Commission’s effective dose limit for workers.  However, many would argue that the safety of workers should be a main priority irrespective of the cost. 

In the end, I can see the benefit for a clean-up operation such as the one in Japan where there are a limited number of workers amongst the earthquake aftershocks that could instigate a serious exposure.  What I cannot see though, is a strong case to bank the cells of all Canadians who work with radiation (40,000 people directly work in Canada’s nuclear industry alone).  More practically, especially in the short term, Canadians should continue to invest in projects like the recent provincial and territorial governments’ investment in a public cord blood banking enterprise that hopes to provide acceptable transplant material for more Canadians in the future.

 

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^[1] - Stem cells typically reside in the bone marrow, but pre-treatment with certain agents (e.g.: Granulocyte Colony Stimulating Factor mobilizes some of the blood stem cells from their bone marrow niche into the blood stream – this allows stem cells to be obtained by drawing blood intravenously instead of requiring bone marrow aspiration)

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Finally, we are left with a practical question to consider in Canada: Is the idea of banking cells from higher risk individuals a good one?