Local and systemic safety of Diffusing Alpha-emitters Radiation Therapy

  Arindam Roy  ,  Lior Arazi  
Unit of Nuclear Engineering, Faculty of Engineering Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel

Diffusing Alpha-emitters Radiation Therapy (“DaRT”) is a new cancer treatment modality utilizing, for the first time, alpha particles for the treatment of solid tumors. The treatment involves intratumoral implantation of sources embedded with a few µCi of radium-224. Once inside the tumor, each source continually releases from its surface the short-lived alpha-emitting daughters of radium, which spread by diffusion and create a lethal high-dose region over several mm through their alpha decays. In contrast to conventional brachytherapy, the use of high-LET radiation makes DaRT effective against hypoxic and radiation-resistant cells.

In this contribution we focus on the radiation safety aspects of DaRT with respect to both local and systemic effects. We show that the rapid fall-off of the radiation field guarantees that collateral damage to adjacent organs fall to negligible levels already ~3 mm away from the treated tumor. We further show that although some of the radioactive atoms released from the source find their way to the circulation and accumulate in different organs, the resulting radiation dose under realistic clinical scenarios is well below the tolerance levels everywhere. In this context, we discuss a biokinetic model that allows calculating the uptake of radioactive daughters in different organs, and present clinical data from blood and urine samples in support of the model predictions.