New Approach to Boron Neutron Capture Therapy (BNCT)

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National Cancer Center Hospital (*1) in Japan completed a facility for a new radiation therapy using neutrons and will start a clinical trial in Spring 2017 to examine the effectiveness of the therapy.  

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image source: National Cancer Center Hospital homepage

 

In the new therapy called BNCT (boron neutron capture therapy), a boron compound BPA (p-boronophenylalanine) is intravenously administered to the cancer patient.  BPA tends to gather to cancer cells.  Thereafter, the cancer cells are irradiated with neutrons.  BPA reacts with neutrons several thousand times stronger than the other elements present in tissue such as hydrogen, oxygen, and nitrogen.  After losing energy as the neutrons penetrate the tissue, the neutrons are absorbed by BPA, which subsequently emits high-energy charged particles that kills the cancer cells.  Thus, BNCT is a therapy that could treat the cancer patients.    

 

So far, BNCT has relied on a nuclear facility as a neutron source, the therapy has not been widely used in clinical institutes.  The National Cancer Center Hospital in Japan developed a smaller and safer BNCT system based on the IAEA (International Atomic Energy Association) standard than the conventional systems without need to rely on a nuclear facility.    

 

Concept

 

BNCT is a noninvasive therapy that does not affect normal cells, but destroys cancer cells. 

 

Since the traditional radiation therapy affects not only cancer cells, but normal cells, it is important how to accurately decide an irradiation site.

 

Theory

 

A compound containing Boron-10 that tends to gather to cancer cells is intravenously administered to the cancer patient. 

 

When the cancer site is irradiated with high energy neutrons, they reaches the cancer cells through the tissue of the patient.

 

When the high energy neutrons reaches boron-10 in the cancer cells, they react with each other and emit alpha particles.  Although the alpha particles receive large energy, they move only for the distance of one cell in the living body.

 

Conventional Approach

 

BNCT is a noninvasive therapy that would effectively treat cancer patients.  So far, only nuclear facilities have been used as sources for low energy and harmless neutrons.  Thus, in Japan, BNCT has been studied in limited nuclear facilities.   

 

Since the nuclear facilities uses nuclear fuels, cancer patients are concerned about exposure to radiations.  In this therapeutic environment, the cancer patients have a risk of safety.  Thus, it was a critical problem how general medical institutions use PNCT as a cancer treatment therapy without relying on nuclear facilities. 

 

New Approach

 

To solve the restriction of relying on nuclear facilities that are neutron sources, a neutron source that uses a linear accelerator has been developed and realized.

 

As a result, standard medical institutes can use BNCT to treat many cancer patients. 

 

*1  National Cancer Center Hospital