What Is Proton Therapy?
Por: Valter Aleixo.
Proton therapy or proton beam therapy is a type of particle therapy that uses a beam of protons to irradiate diseased tissue, most often in the treatment of cancer. The chief advantage of proton therapy over other types of external beam radiotherapy is that as a charged particle the dose is deposited over a narrow range and there is minimal exit dose.
Standard radiation therapy has evolved and improved over the years and is effective in controlling many cancers. However, because X-ray beams are composed of primary photons and secondary electrons, they deposit their energy along the path of the beam, to the targeted tumor and beyond, and deliver radiation to healthy tissues before and after the tumor site. This radiation “exit dose” may cause health issues later because it can damage the normal tissue or organs near the tumor or area of concern.
Who Benefits?
Proton therapy benefits patients whose tumors are solid with defined borders, meaning the cancer has not spread to other parts of the body. It does not require surgery, making it ideal for inoperable tumors
How does it work?
The advantage of proton therapy (also called proton beam therapy) is that the physician can control where the proton releases the bulk of its cancer-fighting energy. As the protons move through the body, they slow down and interact with electrons, and release energy. The point where the highest energy release occurs is the “Bragg peak.” A physician can designate the Bragg peak’s location, causing the most damage to the targeted tumor cells. A proton beam conforms to the shape and depth of a tumor, while sparing healthy tissues and organs.
Understanding how protons work provides patients and physicians with an insight into this mainstream treatment modality. Essentially, protons are a superior form of radiation therapy. Fundamentally, all tissues are made up of molecules with atoms as their building blocks. In the center of every atom is the nucleus. Orbiting the nucleus of the atom are negatively charged electrons. When energized charged particles, such as protons or other forms of radiation, pass near orbiting electrons, the positive charge of the protons attracts the negatively charged electrons, pulling them out of their orbits.
This is called ionization; it changes the characteristics of the atom and consequentially the character of the molecule within which the atom resides. This crucial change is the basis for the beneficial aspects of all forms of radiation therapy. Because of ionization, the radiation damages molecules within the cells, especially the DNA or genetic material. Damaging the DNA destroys specific cell functions, particularly the ability to divide or proliferate. Enzymes develop with the cells and attempt to rebuild the injured areas of the DNA; however, if damage from the radiation is too extensive, the enzymes fail to adequately repair the injury. While both normal and cancerous cells go through this repair process, a cancer cell’s ability to repair molecular injury is frequently inferior. As a result, cancer cells sustain more permanent damage and subsequent cell death than occurs in the normal cell population. This permits selective destruction of bad cells growing among good cells.
Por: Valter Aleixo.
