How Proton Therapy Works

Protons can be calibrated to release the bulk of their energy at certain depths inside the body and conform to the shape of the tumor. This level of precision helps us place more radiation dose exactly at the spot of the tumor, focusing more energy on destroying the cancer while sparing nearby healthy tissue.1

Northwestern Medicine Proton Center also has innovative technology like the vertical CT scanner and pencil beam scanning, which provide additional precision and allow care teams to treat a broader range of tumors and cancers with proton therapy.

What is Proton Therapy?
What is Proton Therapy? To learn more about other tumor types, visit our Video Library.

How Protons Deliver a Proper Dose of Radiation

Both X-ray and proton therapy can be equally effective for treating cancer. However, proton therapy has several benefits. Patients typically experience fewer side effects, less dose to healthy tissue, and reduced risk of developing secondary tumors.

To deposit the proper amount of energy into the tumor, X-rays must irradiate much of the healthy tissue in front of it. Then, they penetrate the tumor and irradiate much of the healthy tissue behind it.

Protons interact in a very different way. They deliver a low dose to the healthy tissue then, at a precise depth, deliver a large burst of energy to the tumor. Shortly after this burst, they stop completely. To treat the entire tumor, additional protons are sent in at lower doses. In this way, protons completely irradiate the tumor while limiting the dose affecting the nearby healthy tissue.

What is proton therapy?

Is Proton Therapy New?

Proton therapy is not a new form of treatment, but it represents the latest advancement in radiation technology. The first patient received treatment with protons more than 50 years ago, and the Food and Drug Administration approved proton therapy as a radiation treatment option in 1988. To date, approximately 131,000 people worldwide have received proton therapy at centers in Europe, Asia and the United States.

Why You May Not Have Heard of Proton Therapy

The Proton Center is one of the few proton therapy centers throughout the Midwest and the only one in Illinois. Some physicians may not be familiar with proton therapy as a treatment option for cancer because of the limited number of facilities in the United States.

The Proton Center is working to increase awareness of this treatment through academic presentations, papers and leadership within the medical community. Our mission is to make proton therapy accessible to everyone who needs it.

Read more frequently asked questions about proton therapy.

Important Milestones in the History of Proton Therapy Treatment

  • 1946: Physicist Robert Wilson first proposes that protons could be used to deliver an increased dose of radiation to a tumor while simultaneously decreasing the exposure of surrounding healthy tissue to radiation.
  • 1950: The first research trials are conducted on patients in Europe. Results are promising, but the inability of imaging technology to accurately "see" or locate many tumors and the inability to direct protons to sites deep within the body meant that only a few patients were appropriate candidates for the treatment.
  • 1970s: Imaging advancement, including computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET), allows physicians to "see" deep inside the body and precisely define the location, size and shape of tumors. This capability, coupled with improvements in proton technology, brought about today's growing interest in proton therapy as an important treatment option for cancer.
  • 1990: The first hospital-based proton treatment center in the United States was built in 1990 at Loma Linda University Medical Center in California.
  • 2010: The Proton Center opens, becoming the first and only facility in Illinois.
  • 2016: The Proton Center adds vertical CT scanning, providing patients with even greater precision and comfort during treatment.