Alpha Radiation Brachytherapy Destroys Solid Tumors

A high-precision, short-range cancer radiotherapy (RT) system releases α particles when radioactive substances decay, effectively killing solid tumor cancer cells while sparing surrounding healthy tissues.

Under development by Alpha Tau Medical (Tel Aviv, Israel), Alpha DaRT (Diffusing Alpha-emitters Radiation Therapy) is based on intratumoral insertion of a radioactive seed (similar in size and shape to fiducial markers) that contains Radium-224 atoms embedded below its surface, with a half-life of 3.7 days. In the process of decay, the Radium atoms release short-lived Alpha-emitting atoms into the tumor, which are known to be highly destructive to all cancerous cells, regardless of their cell cycle stage or level of oxygenation.

When the Radium-224 decays, its short-lived daughters are released from the seed, dispersing into the tumor and emitting high-energy alpha particles that directly damage cell DNA, creating complex double-strand breaks lethal to the tumor. By diffusion and convection, the Alpha-emitting atoms disperse to a therapeutically significant range of several millimeters, delivering a high dose of radiation inside the tumor. Since alpha particles are so potent, the total activity on each seed is very low, and the overall exposure to gamma radiation of surrounding tissues is negligible.

The Alpha DaRT seeds are delivered via disposable and easy to-use applicators inserted through ultra-minimally invasive procedures. Benefits of the brachytherapy treatment included highly potent and conformal delivery; proven efficacy for all solid tumors tested; single-session treatment; effective RT regardless of tumor oxygenation level; quick clinical outcomes; combination with other therapies or re-application; and safety for both patient and clinician, without the need for shielding equipment.

“In 1898 Marie Curie discovered radium, a substance that emits alpha particles radiation, and Curie even then believed that this radiation can aid in cancer healing. Alpha Particles are heavy particles that hit the tumor cells but do not pass into the normal tissue surrounding the tumor or the systemic blood vessels in the rest of the body,” said Uzi Sofer, CEO of Alpha Tau Medical. “Alpha particles can travel only about 1-2 microns, millions of a centimeter, in tissue; that is why there are no side effects.”

Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium-4 nuclei; thus, like helium nuclei, they have a net spin of zero. Due to the mechanism of their production in standard alpha radioactive decay, α particles generally have a kinetic energy of about 5 MeV, a velocity in the vicinity of 5% the speed of light, and a low penetration depth. They are able to be stopped by a few centimeters of air.

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