Actinium
Pharmaceuticals’ Technology |
Alpha
Particles as Cancer Cell Killing Agents
New approaches in the treatment of cancer are necessary to overcome the limited
therapeutic efficacy of currently available therapeutics. Conventional therapies
often have negative side effects which severely limit the therapeutic doses
that can be administered thus severely compromising efficacy of the treatment
and affecting the patient's overall health and quality of life. As a result,
the disease often recurs in time due to the surviving and spreading of cancerous
cells from the original tumor to other areas in the body.
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The key to alpha particle therapy is the control of the extreme power of the alpha particles, which translates to an enhanced ability to kill tumor cells, while reducing the potential or severity of side effects. Alpha particles release more energy over a much shorter distance than beta irradiation, currently employed in radio-immunotherapeutic approaches. In addition, the isotopes chosen have a short half-life, limiting the presence of radiation in the body after they have executed their therapeutic effect.
A Comparison of Alpha And Beta Emitters
Use of alpha-particles as cancer killing agents instead of beta particles
is more attractive for a combination of reasons:
- The alpha's energy is 30
x greater than that of a beta
(typically 6 MeV versus 200 keV) - The electric charge is double (+2 versus -1)
- The mass is 7,000 x heavier (4 mass units versus 1/1800)
As a result, the effective range of alpha particles in tissue is about 5 cell diameters compared with hundreds or thousands of cell diameters for beta particles.
As to cell killing:
- The amount of energy dissipated per unit track length of an alpha particle is 1000x greater than that for a beta particle.
- Non-elastic collisions cause 3x as much cell killing per unit of energy dissipated in tissue, proportionately increasing the effectiveness of cell killing.
- Because the effective range for alpha particles is <5 cell diameters, the killing is confined to tumor cells and thus collateral damage to normal tissue is minimized.
As to side effects:
- The short penetration range and the short half-life of the therapeutic alpha particle emitting isotopes lead to no significant effect on normal tissues and no residual buildup of radiation in the body resulting in a far greater overall health benefit and improved quality of life. In our clinical trials so far, there were no serious effects on any tissue or organ other than target tissue.
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