Isotopes on the ropes

A major problem stemming from the recent shutdown of a Canadian nuclear reactor is more about economics than physics, as nuclear and medical experts asked Congress for funding to solve the current supply-and-demand dilemma surrounding medical radioisotopes.

Last week, a coalition of medical and nuclear-nonproliferation groups sent a letter to the Senate and House appropriations committees, urging leaders to allot funding to the National Nuclear Security Administration, or NNSA, to begin domestic production of medical isotopes using low-enriched uranium. The request followed the unexpected, mid-May closing of a nuclear reactor in Chalk River, Ontario, Canada (June 1, p. 10), which produces one-third of the world’s supply of the isotope molybdenum-99, a uranium processing byproduct used in most imaging procedures. Later this summer, the medical isotope shortage problem will worsen when another reactor in the Netherlands will close down for scheduled maintenance.

The organizations—including the Nuclear Proliferation Prevention Program at the University of Texas at Austin, American Society for Radiation Oncology, Health Physics Society and Carnegie Endowment for International Peace—said producing molybdenum-99 in the U.S. would solve what they refer to as the “double crisis” that includes both immediate and long-term problems. First, without a domestic producer, the U.S. must rely on what the groups describe as “unreliable, aging foreign facilities” for isotopes that American patients need for about 20 million medical procedures a year. But the longer-term—and more dangerous—problem is that all major foreign suppliers use nuclear weapons-grade, highly enriched uranium, the same material used in the atom bomb that the Enola Gay dropped on Hiroshima in August 1945.

In the past, some of the groups in this coalition had different priorities, according to Alan Kuperman, director of the Nuclear Proliferation Prevention Program at the University of Texas at Austin and the letter’s author. For example, he said, the most important issue for nuclear nonproliferation groups had been advocating for restrictions on exports of bomb-grade uranium to produce isotopes, while the medical community said the most important thing was the supply of medical isotopes. But Kuperman said that the recent closure of the Canadian reactor—which also went down for a few months in late 2007—was a “wake-up call.”

“The U.S. nuclear medical community started to realize we cannot depend on those foreign isotope producers,” Kuperman said. “The U.S. uses 50% of all the world’s medical isotopes,” he added. “The answer is: Stop relying on foreign producers and start producing domestically.”

The U.S. used to do this, Kuperman said, but it stopped in the mid-1980s primarily because Canada was producing enough to meet America’s demands, so it was not economical to continue. But things have changed considerably since then. In their letter to congressional leaders, the groups noted that even if the 52-year-old Canadian reactor is temporarily restored, eventually it will close permanently, given that Canadian Prime Minister Stephen Harper said on June 10 that the country will be getting out of the isotope business.

“The world is losing its biggest producer of isotopes,” Kuperman said.

While the organizations did not ask for a specified amount of funding, they did highlight two options for domestic production. One would be for an existing nuclear reactor at the University of Missouri at Columbia to produce these isotopes by irradiating targets of low-enriched uranium. That would require construction of a facility to process those targets, which could cost about $40 million, according to Kuperman’s estimates. The other option the letter mentions is for Babcock & Wilcox Co., a Lynchburg, Va.-based commercial producer, to create medical isotopes in small nuclear reactors with liquid cores of low-enriched uranium.

Robert Atcher is a professor of pharmacy at the University of New Mexico/Los Alamos National Laboratory who completed his term as president of SNM, previously known as the Society of Nuclear Medicine, just last week. While SNM is not a signatory on the letter, the group agrees with the letter’s message, Atcher said.

“We realize how frustrating it is for these periodic interruptions in the supply of the material and the impact that has on the referral patterns of their patients,” Atcher said, adding that SNM is working internally and with the physician community to solve the problem. One way the society is doing this is by urging the CMS to consider reimbursement for sodium fluoride for use in bone-scan imaging.

“When you do bone-scan imaging, traditionally people use a technetium-based agent,” which requires molybdenum-99, said Denise Merlino, SNM’s coding advisor. “That agent is the acceptable standard of practice. Another agent is called sodium fluoride,” she said. Currently, SNM is leading other groups in gathering literature for the CMS, which she said has agreed to consider published evidence. Then providers faced with the molybdenum-99 shortage could use sodium fluoride in PET scans, a diagnostic imaging test used to determine the presence and severity of cancers, neurological conditions and cardiovascular disease.

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