Radium is a chemical element with the symbol Ra and atomic number of 88. It is a naturally occurring alkaline earth metal. It is formed by the radioactive decay of uranium and thorium which are found in many compounds in the environment. All thirty-three isotopes of radium are highly radioactive. The only use for radium is in medical treatments for cancer.
Radium-224 is an isotope of radium that has a half-life of about three and a half days. While many cancer treatments are toxic for the patient, the alpha particles emitted by Ra-224 are deadly to cancer cells but leave healthy tissue alone. The alpha particles create complex double strand DNA breaks that kill the cancerous cells. The problem with Radium-224 is that the emitted alpha particles have a very short path length in the tissue of tumor. They often cannot reach all the parts of a tumor distant from the injection point.
Itzhak Kelson and Yona Keisari are professors at Tel Aviv University. They developed a new Ra-224 therapy which is referred to as Diffusing Alpha-emitters Radiation Treatment (ALPHA Dart) in 2003. An ALPHA Dart “seed” is inserted into a tumor. It contains Ra-224 atoms below the surface of the seed. In the process of radioactive decay, the seed emits Ra-224 atoms which in turn emit short lived alpha particles into the tumor. Diffusion and convection processes disperse these alpha particles are to a therapeutically significant distance of several millimeters. The Ra-224 seed powers the spread of the alpha particles to all parts of a tumor. The ALPHA Dart treatment is the first time that Ra-224 has been used to treat solid tumors.
Alpha particles hardly diffuse at all in healthy tissue. This means that patients are not threatened with toxic side-effects and ALPHA Dart therapy is very safe. All solid tumors tested have been diminished if not outright destroyed. In a recent Ra-224 study, one hundred percent of the tumors treated shrank. In seventy eight percent of the treatments, the tumors were totally destroyed.
ALPHA Dart treatment is suitable for the destruction of cancer cells regardless of oxygen level or cell life cycle. This makes it suitable for treating tumors that resist conventional gamma ray treatments. ALPHA Dart treatment is rapid and improvements in the patient’s condition can occur in a few days from the date of treatment. ALPHA Dart seeds are implanted once with a local anesthetic. ALPHA Dart can be combined with other treatments such as immunotherapy and chemotherapy. There is negligible exposure of the doctors and nurses to gamma radiation from the ALPHA Dart seeds. Alpha Tau has developed minimally invasive and cheap applicators that can treat a variety of tumors in different areas of the body. ALPHA Dart applicators are disposable, and the treatment does not require special equipment or special shielding so it should be cost effective in the treatment of millions of people suffering from cancer.
In 2016, Uzi Sofer founded a private company named Alpha Tau Medical and now serves as the CEO of the company. The number of employees at Alpha Tau has grown to forty from the original ten. Trials of the new ALPHA Dart therapy are underway in Israel, Canada, Japan, Russia, Italy and in the United States.