Understanding the History, Usefulness of Nuclear Medicine, Radiopharmaceuticals in Fighting Cancer

Although nuclear pharmacy seems to exist as an abstract practice due to being a new type of pharmacy, nuclear pharmacy is just pharmacy, explained Christopher J. deHoll, PharmD, BCSCP, assistant director of pharmacy at the Moses H. Cone Memorial Hospital, in a presentation at the American Society of Health-System Pharmacists 2022 Summer Meeting.

“This is still pharmacy. A radiopharmaceutical is still a pharmaceutical,” deHoll said. “It’s everything you’ve studied and known; all we’re going to do to it is add a little radiation.”

For background on the development of radiopharmaceuticals, deHoll explained that in 1946, a year after atomic bombs were dropped on Hiroshima and Nagasaki, physicians treating Japanese survivors from the bombings were discovering some interesting occurrences in the bodies of their patients. When the bombs were developed, deHell explained that the Manhattan Project was probably only considering the bombs’ potential explosive power and were not thinking about what uranium-235 might become after it exploded. During the treatment of survivors, physicians discovered one of the fallout products of these bombs were iodine-131.

“They found that some of the Japanese survivors they were treating had no thyroid,” deHoll said. “They then linked it to iodine-131. Then someone had the bright idea, ‘Wait, if you have someone with thyroid cancer, would it work as a treatment?’ And it did. This is the birth of nuclear medicine.”

Before the discovery of this treatment for thyroid cancer, de Holl noted that there were no real treatments for the disease. The treatments devised for thyroid cancer before nuclear medicine verged on barbarism, deHoll explained.

“With nuclear medicine, [the thyroid] was treated, the cancer just receded, and there were no side effects—except that they couldn’t be around the people they loved for about 3 days as the iodine got out of their system,” deHoll said. “But this was the birth of nuclear medicine.”

In terms of the usefulness of radiopharmaceuticals in hospitals today, deHoll explained that they are primarily used for diagnostic imaging. Considering there are only approximately 450 nuclear pharmacies in the United States, these pharmacies are servicing the vast majority of the radiopharmaceutical diagnostic imaging needs of hospitals across the country. Because of this, nuclear pharmacies are generally centrally located within the country.

deHoll noted that radiopharmaceutical agents have typical pharmacokinetic properties in their distribution to certain organs, such as with the diagnostic isotope Tc-99m, which allows for precise imaging by binding to the pharmaceutical and emitting gamma radiation, similar to X-rays. Specifically, the advantage of using radiopharmaceuticals over traditional modalities, such as CT scans, MRIs, or ultrasounds, is that they also allow for visualization of perfusion and metabolism in a tissue of interest.

“You can use an MRI or ultrasound to see the structure of the heart or the pancreas, but the thing is, radiopharmaceutical diagnostics are used to show perfusion. An ultrasound can show you the shape of the heart, but this shows you the perfusion around the heart and in the coronary arteries. It also shows metabolism, which is something that is unique to radiopharmaceuticals and is especially useful for cancer imaging,” deHoll said.

Diagnostic imaging is the bread and butter of the nuclear medicine practice, deHoll explained. Approximately 90% of all procedures conducted using radiopharmaceuticals are diagnostic in nature.

The most commonly used radiopharmaceuticals in diagnostics are Tc-99m sestamibi and Tc-99m tetrofosmin, which are both used for myocardial perfusion; Tc-99m medronate, which is used for skeletal imaging; F-18 fludeoxyglucose, which is used for cancer tumor imaging; and Tc-99m mebrofenin, which is used for gallbladder imaging.

“Essentially, what they’re doing in a nuclear pharmacy is taking Tc-99m and they use an eluate, which is the isotope in normal saline, and they have a cold kit, which is just a sterile vial with lyophilized powder, and it has the drug in it, but also the ingredients to take the pharmaceutical and bind it to the technetium,” deHoll said.

The vials used for the cold kits are similar to the unreconstituted drug vials commonly used in conventional sterile compounding, deHoll explained. These cold kits containing the drug and a number of ingredients that facilitate the binding of the drug to the isotope are then delivered to hospitals for use in diagnostic imaging.

Within hospitals that use these radiopharmaceuticals, deHoll explained that any unease around the use of radiopharmaceuticals is just due to a lack of familiarity with the field.

“I like the quote that the author H.P. Lovecraft [wrote], ‘The greatest fear we have is fear of the unknown,” said deHoll. “I want [nuclear pharmacy] to be tangible for people. Some people find that if you know USP <797> [and] you know USP <800>, this is not far away from that. You can very easily understand it [so you can] use USP <825> in your hospital system in a way that can be very beneficial.”

REFERENCE

deHoll CJ. USP <825>: Radiopharmaceutical Compounding Finally Gets a Chapter of Its Own. Presented at: ASHP Summer Meeting 2022; June 14, 2022; Phoenix, AZ.