About Proton Therapy

What is proton therapy?

Proton therapy is an advanced form of radiation therapy. This form of radiation therapy uses protons—positively charged atomic particles—instead of the photons used in standard radiation.

Proton therapy can treat many of the same tumors that are treated with standard radiation. Protons can be precisely controlled to release much of their energy directly in the tumor, reducing damage to nearby healthy tissue.1 As a result, patients can receive higher doses and experience far fewer side effects from treatment.1

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How does proton therapy work?

X-rays and protons can be equally effective at destroying cancer cells, but there are some important benefits of proton therapy – patients typically experience fewer side effects, less exposure to radiation and a reduced risk of developing secondary tumors.

Protons can be manipulated to release their energy at precise depths. Whether the targeted tumor is near the skin surface or deep inside the body, protons are able to deposit much of their energy at the exact tumor site.

The peak of the proton-radiation dose (called the Bragg Peak) is set so it releases the radiation when it hits the tumor; immediately after that point, the dose falls to almost zero. Less radiation reaches the healthy tissue in front of the tumor, and almost none reaches the healthy tissue behind the tumor, resulting in less damage to healthy tissue.1 Patients often experience fewer of the short- and long-term side effects that typically accompany standard radiation.1-7 In addition, because more energy can be deposited directly in the tumor, a higher dose can often be delivered, leading to more effective treatment.1

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How do proton beams destroy cancer cells?

When protons reach the nucleus (or center) of cancer cells, they transfer energy to the cells' electrons causing a series of interactions, or ionizing events, that damage the DNA of the cancer cells. The damaged cells then die because they can no longer divide.

How many patients have received proton therapy?

Since the first hospital-based proton treatment center opened in California in 1990, nearly 40,000 people have received proton therapy in the United States and almost 100,000 people worldwide. Experts conservatively estimate that about 250,000 cancer patients in the United States could benefit from proton therapy.

Is proton therapy experimental?

The first patient received treatment with protons more than 50 years ago, and the U.S. Food and Drug Administration approved proton therapy as a radiation treatment option in 1988. To date, almost 80,000 people worldwide have received proton therapy at centers in Europe, Asia and the United States.

What is the history of proton therapy?

In 1946, physicist Robert Wilson first proposed 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.

By 1950, the first research trials were being conducted on patients in Europe. Results were 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.

Advances in imaging, including computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET), now allow 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.

Can proton therapy be used in combination with other cancer treatments?

In many cases, yes. Proton therapy can be used in combination with chemotherapy, as a follow-up treatment to surgery, and in combination with standard radiation treatment. In cases where a tumor has reoccurred after previous treatment with traditional radiation therapy and cannot be treated again with X-rays, proton therapy is a treatment option.

The Northwestern Medicine Chicago Proton Center has joined with several medical centers to provide patients with additional cancer services.

What are the potential side effects of proton therapy?

Patients should not feel pain or discomfort during treatment sessions. There may be side effects during or after treatment, but they are generally minor, less frequent and less severe than the side effects that can result from standard radiation therapy—primarily because less healthy tissue is exposed to radiation in proton therapy. Depending on the location of your tumor, side effects may include skin irritation in the direct path of the proton radiation, tiredness and hair loss in the area being treated. Your doctor will discuss with you the specific side effects that you may experience based on your treatment plan.

Can proton therapy be used in combination with other cancer treatments?

In many cases, yes. Proton therapy can be used in combination with chemotherapy, as a follow-up treatment to surgery, and in combination with standard X-ray radiation treatment. The Chicago Proton Center has joined with several medical centers to provide patients with additional cancer services.

Is there continuous research on proton therapy?

Yes, the medical community continues to conduct research studies on proton therapy. Major institutions like MD Anderson Cancer Center and Massachusetts General Hospital have many ongoing clinical trials to help find improvements in treating cancer with proton therapy. As a dedicated provider of proton therapy, the Chicago Proton Center is currently participating in several clinical trials.

If you are interested in participating in a trial, please speak with a doctor or a nurse at the Chicago Proton Center.

Learn more about our clinical trials

Is Proton Therapy Right For You?

What are some of the common tumor sites treated with proton therapy?

Certain types of cancer are more appropriate for proton therapy than others. While research continues to support using protons in more types of tumors, protons are primarily used to treat:

Can children receive proton therapy?

Yes, in fact, proton therapy is particularly effective for children who need radiation therapy. Clinical studies indicate that proton therapy reduces the likelihood of developmental problems as well as secondary tumors which can occur years later.3,5,8 Because a child’s body is small and still developing, the damage to nearby healthy tissue and organs from standard radiation can be harmful. This damage can cause growth abnormalities, reductions in IQ and other complications.9 New tumors can also develop later in the child's life. A growing body of research is confirming the advantages of using proton therapy for children.

Can proton therapy be used for all types of cancers in all patients?

Proton therapy is not appropriate for all types of cancers or all patients. Proton therapy is most effective in treating solid tumors that are well-defined and localized—those that have not spread to other areas of the body. If the tumor has spread (metastasized), proton therapy may still be an option, depending on the extent of the metastasis and other factors. Only a healthcare provider can determine the best approach for a patient's unique condition.

Why is proton therapy an option for only certain types of cancer?

Because of the limited number of proton treatment facilities worldwide, physicians have focused on using proton therapy primarily for tumors near critical organs, such as the heart and bladder, or structures such as the spine. The types of tumors treated will continue to expand as research continues and doctors develop treatment plans for more types of tumors.

Benefits of Proton Therapy

How is proton therapy different from standard radiation treatment?

Proton beams deposit much of their energy directly in the tumor, reducing damage to healthy tissue and allowing patients to receive higher, more effective doses.1 Less damage to healthy tissue and organs can result in fewer side effects than standard radiation therapy, thus improving patients' quality of life and long-term health.1-7 Standard radiation can be harder to control and deposits more radiation in healthy tissue as it enters and leaves the body.

Are X-rays (photons) as effective as protons in destroying tumors?

X-rays and protons can be equally effective in destroying cancer tumors. The difference is that X-ray treatments damage more healthy tissue in the process. X-rays release much of their energy shortly after penetrating the skin, damaging healthy tissue and organs on their way to the tumor and again as they leave the body.

Why is proton therapy often considered a better treatment option compared to standard X-ray radiation therapy?

Because proton beams deposit more of their energy directly in the tumor, less radiation reaches the healthy tissue in front of the tumor, and almost none reaches the healthy tissue behind the tumor.1 Patients typically experience fewer short- and long-term side effects than what often accompanies standard radiation therapy. In addition, because more radiation can be deposited directly in the tumor, a higher dose can often be delivered, leading to more effective treatment.1

Video Library

We have created a library of several videos for you with key information such as:

  • What is Proton Therapy?
  • Benefits of Proton Therapy
  • Real patient stories/testimonials regarding specific tumor types
  • Virtual tour of the proton center