The Crocker Nuclear Laboratory at the University of California, Davis, has received a $340,000 grant from the Department of Energy to manufacture a rare isotope, astatine-211, for medical use. The award is part of a federal program to produce critical isotopes for U.S. science, medicine and industry needs. The magnets at the heart of UC Davis’ 53-year old cyclotron were used to discover astatine almost 80 years ago. 

Astatine is the rarest element on Earth and astatine-211 shows promise as a tumor-killing treatment for some cancers. But the isotope is not available in amounts large enough for clinical testing. The new project aims to test the feasibility of making astatine-211 at the Crocker Lab. 

“We are excited to again make medically useful isotopes at the Crocker Nuclear Laboratory,” said lab director Eric Prebys, professor of physics in the UC Davis College of Letters and Science. 

Setting the stage for future cancer treatment

Astatine-211 is a candidate for targeted alpha therapy, a treatment that delivers radiation directly to cancer cells. Because astatine-211 only emits alpha particles, which travel less than a millimeter in human tissue, the radiation damage is localized to tumors. However, the short 7.2-hour half-life of astatine-211 means the isotope must be made and used the same day.

UC Davis scientists will produce astatine-211 by bombarding bismuth-209 with alpha particles. The project takes advantage of the unique capabilities of the Crocker Lab, one of the few cyclotrons in the U.S. that can produce an alpha particle beam intense enough to create astatine-211. Cyclotrons like the one at Crocker Lab use a magnetic field to guide charged particles along a spiral path, accelerating them to high energies.

The DOE grant will fund the design and construction of new equipment to prove the feasibility of production and recovery of astatine-211 at the Crocker Lab facilities. In the future, Prebys and his colleagues plan to seek funding for full-scale production of the isotope. 

Crocker cyclotron comes full circle

The astatine-211 project brings the Crocker cyclotron back to its beginnings — its main magnet was at heart of the equipment that first synthesized astatine in 1940. 

“It’s exciting to find new uses for this cyclotron, particularly one that calls back to its origins,” Prebys said.

The discovery of astatine filled a gap in the periodic table. The element was produced at a UC Berkeley cyclotron that discovered many new elements, including plutonium. When the Berkeley cyclotron was decommissioned, its magnets were moved to UC Davis to be used for the Crocker’s 76-inch cyclotron, which began operation in 1966. 

A history of helping patients

Medical isotopes have long been a part of the Crocker Lab. In 1972, UC Davis scientists developed a new method for making iodine-123, a thyroid cancer diagnostic tool now available from commercial suppliers. The lab has produced nearly 25 different medically useful isotopes over the years; however, the cyclotron has not been used to produce isotopes since the 1990s.   

The laboratory has also treated more than 2,100 people for a rare form of eye cancer called uveal melanoma, with treatment overseen by the UC San Francisco Department of Radiation Oncology. The treatment relies on proton beam therapy, in which the beam penetrates the eye and then stops, targeting its cancer-killing energy on the tumor itself.