La escasez médica del isótopo podía afectar a 20.000 pacientes

por Brendon Nafziger, DOTmed News Associate Editor | March 25, 2010
Nuclear medicine faces one
of the worst shortages
ever of molybdenum-99,
a radiosiotope used
for cardiac and cancer
Overlapping outages of several high-profile nuclear reactors are causing what the Society of Nuclear Medicine calls "one of the most significant disruptions ever" in the supply of medical isotopes.

Starting last Sunday and lasting until April 11, SNM predicts the world supply of an isotope critical to diagnosing heart disease and bone cancers will drop down to 10 or 20 percent of its normal level.

The isotope, molybdenum-99, is the parent of technetium-99, used in nearly 80 percent of all nuclear medicine and molecular imaging studies, according to SNM.

Based on the society's projections, Robert W. Atcher, Ph.D., past president of SNM and chair of their Medical Isotope Task Force, estimates that close to 20,000 patients could be forced to reschedule tests that help diagnose heart disease by measuring blood flow and that help find bone metastases.

"They'll either be delayed until there's time to have a better supply of material we need, or they'll be shifted over to another imaging procedure," he tells DOTmed News.

But while some alternatives to the blood flow exams, known as cardiac perfusion tests, or bone imaging studies exist, they have serious problems, says Dr. Atcher. They're less effective, costlier, and expose patients to more radiation, he notes. And in the case of angiography, a pinch hitter for cardiac perfusion, they're more invasive.

While some doctors have started switching to thallium-201, a potassium analogue that gives similar information about blood flow, it has performance troubles. With lower photon energy, it produces more scatter and self-absorption in overweight patients, Dr. Atcher says. And even without this problem, supplies of the isotope are still too low to satisfy the world's medical needs.

"Production for cardiac imaging has not kept up with demand for cardiac imaging. Even though producers have ramped up production for [thallium-201], we still can't meet the market," says Dr. Atcher.

Simultaneous outages

The throttling of supplies of the isotope comes from an unfortunate coincidence: a number of reactors are down at the same time, including the simultaneous outage of two of the biggest isotope-producing workhorses. The High-Flux Reactor in Petten, the Netherlands is offline, undergoing six months of repairs, and the National Research Universal Reactor in Chalk River, Ontario is also out, with an oft pushed-back restart date somewhere in May or June, at the earliest.

And though the FDA recently approved U.S. use of isotopes from the Maria reactor in Poland, one of the first new medical isotope-making reactors to enter the market in years, thanks to a deal with Covidien, no shipments have reached American shores yet. Even when they do, they won't fill the gap left by NRU: the Canadian giant was thought to account for 40 percent of the world's supply, and possessed back-up capacities allowing it to churn out larger-than-usual amounts of isotopes in the event of a crisis, such as the one the industry is facing now.