Boron Neutron Capture Therapy (BNCT) is a non-invasive therapeutic technique for treating invasive malignant tumours. It relies on the use of neutrons for the generation of energetic alpha particles to destroy cells within the tumour, but not in the surrounding tissue. Recent breakthroughs in accelerator technologies are enabling wider use of this very targeted technique – and the IAEA and Japan’s Okayama University have now signed an agreement that provides a three-year framework for enhanced cooperation in this area.
Patients undergoing BNCT are given a boron-based reagent, often injected intravenously, which accumulates in cancer cells. When a stable boron isotope (boron-10) of the reagent is hit by a beam of neutrons in the cancer cells, it captures neutrons, which causes a nuclear reaction and creation of energetic helium (alpha particle) and lithium nuclei. The nuclei deposit their energy within the tumour cell, causing damage and cell death. The tumour is targeted by selectively introducing the boron reagent into tumour cells, and not by aiming the beam at the cells, as in other radiation therapies, in which healthy tissue still may get damaged as a result. The high biological effectiveness of this procedure and the precisely targeted cell damage are major advantages of BNCT in clinical therapy.
The effectiveness of BNCT depends mainly on the boron concentration and its distribution in targeted tumour cells, and one of the main R&D challenges remaining is how to increase this concertation. Significant progress has been made over the last few years in optimizing boron compounds and controlling their accumulation in tumour cells. Recently, the most common boron carrier – boronophenylalanine (BPA) – labelled with fluorine-18 (F-BPA) has been developed and successfully applied for monitoring the pharmacokinetics of BPA with positron emission tomography (PET), which allows obtaining information about the tumour as well as evaluating the boron accumulation in both the tumour and in normal tissue. However, further challenges remain:
“The BPA in use currently contains only one boron-10 isotope per molecule. For BNCT to be more successful in destroying the tumour cells, cell targeting agents containing a higher number of boron-10 isotopes in their structure should be developed,” explained Danas Ridikas, Head of the IAEA Physics Section. “This will be one of the main focus of our R&D cooperation activities with Okayama University.”
