Isotope shortage delaying cancer and heart tests

A worldwide shortage of radioactive isotopes is causing delays in some imaging tests for cancer and heart patients at area hospitals, doctors say.

The isotopes enable doctors to create images of the heart that show how well it is pumping or whether cancer has progressed to the bones. But the supply has been sporadic for several months and the shortfall could persist for years because of the shutdown of two nuclear plants, experts said.

The shortage is causing delays for some stress tests at the Jefferson Heart Institute in Center City.

Tests for cancer that has spread to the bones are down this summer at Fox Chase Cancer Center in Northeast Philadelphia as doctors conserve isotopes for the most pressing cases.

Abington Memorial Hospital in Montgomery County has switched to an older isotope, thallium, to measure blood flow. The aim is to conserve the limited supply of newer radioisotopes for diagnostic tests that have no alternative compounds available.

The most recent shortage of isotopes started in May when the 52-year-old National Research Universal (NRU) reactor in Chalk River, Ontario, was shut down because of a heavy-water leak.

The reactor, which produces one-third of the world's supply, remains down with no clear timeline for when - or if - it will return to service.

This summer the shortage is being worsened by periodic shutdowns for scheduled maintenance of the 48-year-old Petten reactor in the Netherlands. That reactor, which accounts for another third of the world supply, is scheduled for a six-month closure next year.

"That is just going to be disastrous [in 2010] if the Canadian reactor hasn't come back online," said Michael M. Graham, director of nuclear medicine at the University of Iowa and president of the Society of Nuclear Medicine.

Each day, more than 34,000 nuclear-medicine procedures are performed in the United States, said Steven R. Mattmuller, chief pharmacist at Kettering Medical Center in Ohio.

"We are in a pickle now," he said. "There are plans to get us out of it, but the next five to seven years will be very challenging for us."

Unlike X-rays and other external scans, medical isotopes are injected into patients. The isotope is "tagged" with various compounds so it can be detected in the organ or body part being examined. Cameras then record the emitted radiation and feed that data to computers to generate images of the organ or tissue.

A shutdown of the two reactors at the same time would cause more shortages of the isotope molybdenum-99, a precursor to technetium, a key material in nuclear medicine that is used for 80 percent of diagnostic images. Of those, about half are used to examine heart function and blood flow. The isotopes also help doctors detect life-threatening blood clots in the lungs and the spread of cancer.

The same reactors also produce iodine-131, a radioisotope used to treat thyroid cancer and hyperthyroidism, Graham said.

"In both cases, patients will have their diagnosis or therapy delayed," he said. "It is going to have serious health consequences for a large number of people."

In some cases, the lack of isotopes has meant postponing surgery because patients were unable to get cardiac stress tests before procedures, such as knee replacements.

For others, it has meant more expensive and invasive procedures such as cardiac catheterizations.

In these procedures, a doctor inserts a thin plastic tube into a blood vessel and advances it into the coronary arteries to assess flow, or farther into the heart itself to measure its pumping ability.

These procedures are more invasive and expensive than standard nuclear imaging, yet doctors are resorting to them more often when the older imaging fails to give a clear result, said cardiologist Mark F. Victor, head of Cardiology Consultants of Philadelphia, the region's largest private group of heart doctors.

Thallium, the older isotope, doesn't give doctors quite as good an image, especially in patients who are overweight and obese - those most prone to heart problems, Victor said.

Despite the need for the materials, experts are concerned that the United States has not been doing enough until recently to to fix the problem.

"This is a worldwide issue, but I think the U.S. is probably a bit more vulnerable than others," said Dale Klein, a member of the Nuclear Regulatory Commission and one of the few government officials to sound a warning on the issue. "We are the largest user of radioisotopes, but we have no source of our own."

"Petten and NRU need to limp along until there can be a permanent worldwide solution," he said.

Christopher L. Hansen, a nuclear cardiologist at Thomas Jefferson University Hospital, said the heart institute was still getting the technetium doses, but not as many as it wanted.

"We are doing what we can to get patients through, but patients have longer waits to get a stress test right now," he said. "Many centers have gone to [older] thallium. . . . We have not yet switched."

At Fox Chase, chief of nuclear medicine Michael Yu said the number of scans was down 6 percent in June and an additional 10 percent in July.

"Some emergency studies will be a little bit difficult for us to do," Yu said.

In a preemptive move, Abington switched to thallium for all its stress tests, which account for about half of the medical isotopes it uses.

"There is a great potential to impact patient care in the long run," said Annette Yacovone Griffith, a specialist in nuclear medicine at Abington. "In the short run, everyone is just making adjustments."