The World's Rarest Element Might Help Fight Cancer

The Resonance Ionization Laser Ion Source, which was instrumental to the new study, at ISOLDE, courtesy the University of York

Never heard of astatine? You're not alone—it's the rarest naturally-occurring element on Earth. In fact, if you want to go find some astatine, have a blast: It's been estimated that, at most, there's just a couple grams of the stuff in all of the Earth's crust at any one time, formed from the natural decay of elements such as uranium. But rare as it is, new research from the folks at CERN suggests it could be used in a novel cancer therapy.

The element (number 85 on the Periodic Table, for those of you filling out your charts) was discovered in 1940, when Dale Corson decided to bombard bismuth with alpha particles, yielding an isotope of astatine with a half-life of about eight hours. Some of its less stable isotopes have a half-life of just nanoseconds, making it all but impossible for scientists to learn much at all about the element. Corson and his team decided to name the element after the Greek word for "unstable."

But, as they tend to do, scientists at CERN have a solution for seemingly impossible problems: Using their fancy radioactive isotope facility, known as ISOLDE, which features a laser spectroscope able to take specific measurements of molecules in nanoseconds, they've been able to study the atomic structure of astatine for the first time. And it turns out the stuff might be ideal for a new type of cancer therapy.

"Astatine is of particular interest because its isotopes are interesting candidates for the creation of radiopharmaceuticals for cancer treatment by targeted alpha therapy," Andrei Andreyev, lead researcher of the CERN study, said. The research was published in Nature Communications (PDF here) on Thursday.

The Resonance Ionization Laser Ion Source helps ionize rare elements like astatine at the ISOLDE facility. Courtesy the University of York

According to the NIH, targeted alpha therapy uses radioactive particles of heavy elements, which "release enormous energy over a short distance … providing a more specific tumor cell killing ability without damage to the surrounding normal tissues."

"Even though these α-emitters have favorable properties, the development of TAT has been limited by high costs, unresolved chemistry, and limited availability of the radionuclides," the NIH report continues. "To overcome these limitations, more potent isotopes, additional sources, and more efficient isotope production methods should be addressed."

Astatine might be one of those more potent isotopes. Its extremely short half life means that radiation exposure to patients would be lower than existing treatments, and it generally decays back into bismuth, a heavy metal with extremely low toxicity. 

CERN observed a couple things it wasn't expecting with astatine, namely a rare type of nuclear activity.

"This development allows several new phenomena to be investigated, such as the size of astatine nuclei, along with a very exotic type of nuclear fission," Andreyev said. His team has started a series of new experiments to see if more stable types of astatine exist and to determine how researchers can harness it for targeted alpha therapy. 

Topics: Cancer, radiation, radiation research, cern

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