Nuclear Regulatory Commission Public Meeting
September 29-30, 2008
Security and Continued Use of Cesium-137 Chloride Sources
Issue 1 – Alternatives to the use of CsCl sources in compressed powder form
Issue 2 – Use of alternative technologies
Jed Gorlin, MD
AABB Board of Directors
AABB is an international association dedicated to advancing transfusion and cellular therapies worldwide. Our members include more than 1,800 hospital and community blood centers and transfusion and transplantation services as well as approximately 8,000 individuals involved in activities related to transfusion, cellular therapies and transplantation medicine. For more than 50 years, AABB has established voluntary standards for, and accredited institutions involved in, these activities. AABB is focused on improving health through the advancement of science and the practice of transfusion medicine and related biological therapies, and developing and delivering programs and services to optimize patient and donor care and safety.
Blood components are irradiated to prevent transfusion associated-graft-versus-host disease (TAGVHD) from white blood cells in cellular blood components such as red cells or platelets. Once established, TAGVHD is usually untreatable and often fatal. While not all patients require irradiated blood, those whose immune systems are compromised or who are receiving blood from immunologically similar donors, such as family members are at particular risk of this complication. Hence, it is imperative to balance the risks and benefits of phasing out Cesium in favor of alternative strategies. Respondents to the 2007 National Blood Collection and Utilization Survey reported that 2,322,000 blood components were irradiated in 2006. Many of these are concentrated at institutions that take care of cancer patients.
The conversion to an alternative technology, to include isotopes other than cesium-137, for blood component irradiation would present many challenges to the blood community. When determining policy, one must balance both risks and benefits of a proposed intervention, as well as costs and benefits. The risks of maintaining a cesium source irradiator are described in Radiation Source Use and Replacement (2008), National Research Council ISBN: 978-0-309-11014-3, whereas, the risks of removing the cesium source irradiator are less well addressed. The greatest risk is the potential for inadequate treatment and development of TAGVHD to patients, if alternatives are either unavailable or not functioning. Currently, there are several establishments that utilize X-ray technology for the irradiation of blood products. The conversion to X-ray technology is fraught with both positive and negative attributes but several factors are problematic. While most centers have backup plans in the event that their irradiator becomes unavailable, these are rarely utilized since cesium irradiators are functionally so robust and durable. In contrast, the track record for the X-ray irradiators, while good, still has significantly more down time for X-ray source and power source replacement – greater than 30-days (21.4%) as compared with 0-2-days (92.4) for cesium source irradiators. In addition, decreased throughput capacity of some of the X-ray devices could lead to delay in providing patient therapy. In balancing the cost benefit ratio, the purchase of an X-ray irradiator would have to be considered a new unplanned cost, for most facilities own their cesium-137 irradiator and the annual operational cost of a cesium-137 irradiator (less than $10,000 for 74.6% of survey respondents) is far less than an X-ray irradiator (61.5% of responded less than $10,000 but 84.6% do not cover X-ray tubes and power sources – the most frequently replaced parts which could cost up to $40,000). Specifically, as outlined in Chapter 10 of the NRC document over the life expectancy of the X-ray equipment, one might expect to incur at least $318,000 in additional service and maintenance costs per device. We posit that the costs outlined in Chapter 10, may be grossly underestimated since the reliability and throughput of existing X-ray devices may be sufficiently lower than cesium-137 irradiator, that the purchase of two X-ray irradiators to replace one cesium-137 irradiator may be necessitated. The requirements for dose mapping, validation, and training will remain.
In addition to the significant obstacles for the implementation of X-ray technology, replacing a cesium source irradiator with a cobalt-60 irradiator is not feasible. The sheer weight of cobalt-60 radiation equipment due to the increased radiation barrier makes them an impractical solution, for many current installations. While many irradiators are currently located in blood centers, many more are in hospitals, often, not on basement or ground floor levels. Thus, to install a cobalt-60 irradiator on a level other than the basement would require significant facility structural modifications.
The use of pathogen inactivation technology has significant potential to abrogate the need for blood product irradiation. However, such technology is not licensed for use in the United States and is not anticipated to be licensed in the near future.
In conclusion, even though X-ray technology is available and is used by a small part of the blood community, there are significant logistical, operational and financial obstacles that will prevent an immediate or mass conversion to their use. Therefore, we recommend that establishments not be required to convert to X-ray technology over any period of time that cannot ensure complete capacity to irradiate all products requiring treatment.