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How Does Proton Therapy Work?

View Cancers Treated with Proton Therapy

Proton therapy is the most technologically advanced method to delivery radiation treatments to cancerous tumors available today.  The unique characteristics of how protons interact within the human body allow it to deliver curative radiation doses while reducing doses to healthy tissues and organs resulting in fewer complications and side effects than standard radiation therapy. Understanding how proton therapy works provides patients and physicians with insight into the clinical advantages of this treatment modality.

Proton Therapy Infographic

Fundamentally, all tissue cells 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 protons 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. Because of ionization, the radiation damages molecules within the cells, especially the DNA. Damaging the DNA destroys specific cell functions, particularly the ability to divide or proliferate.  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.

Protons stop, X-rays do not.

Both standard radiation therapy and proton therapy work on the same principle of damaging cellular DNA.  The major advantage of proton therapy treatment over standard radiation therapy, however, is that protons slowly deposit their energy as they travel towards the cancerous tumor and then due to a unique physical characteristic called the Bragg Peak, deposit the majority of the radiation dose directly in the tumor and travel no further through the body. This results in less healthy tissues and organs receiving unnecessary radiation thereby reducing unwanted complications and side effects. Standard radiation therapy utilizes x-rays which deposits the majority of the radiation dose immediately upon entering the body while traveling to the tumor. Unlike protons, after depositing radiation dose in the tumor the x-rays continue traveling through the body until exiting out the other side resulting in the delivery of unnecessary radiation to healthy tissues and organs.  Simply put, protons STOP after depositing the radiation dose in the tumor, x-rays do not.

These unique advantages of proton therapy lead to the potential for fewer harmful side effects, more direct impact on the tumor, and increased tumor control.