Proton therapy

Overview

Proton therapy is a type of radiation therapy. Radiation therapy uses high-powered energy to treat cancer and some noncancerous tumors. Radiation therapy using X-rays has long been used to treat these conditions. Proton therapy is a newer type of radiation therapy that uses energy from positively charged particles called protons.

Proton therapy works by aiming beams of energy at the body. The energy from the proton beams damages the DNA inside the cells in its path. Healthy cells often can repair this damage. But the cancer cells can't. The damage stops the cancer cells from growing and multiplying.

Proton therapy has shown promise in treating several kinds of cancer. For some cancers, studies suggest that proton therapy may cause fewer side effects than traditional radiation, since healthcare professionals can better control where proton beams deliver energy. But few studies have compared long-term results of proton and X-ray radiation therapy, so it's not clear whether proton therapy is more effective at prolonging lives.

Proton therapy isn't widely available. However, new proton therapy centers are being built in the United States and in other countries.

Proton therapy vs. traditional radiation therapy

Proton therapy and traditional radiation therapy both use powerful energy beams to treat cancer and noncancerous tumors. But each treatment uses a different kind of energy.

• Traditional radiation therapy also is called photon therapy. Photon therapy uses high-energy X-rays to target and destroy cancer cells. The photons work like a beam of light. They enter the body from one side, travel through the area being treated, and then exit from the other side.
• Proton therapy uses the energy from positively charged particles called protons. Unlike photons, which pass all the way through the body, protons enter the body, release most of their energy right where the cancer is, and then they stop. This means proton therapy may help lower the amount of radiation that healthy tissues and organs receive.

Proton therapy may allow healthcare teams to give larger doses of radiation, especially to cancers and tumors that are near important structures.

Why it's done

Proton therapy treats cancer and some noncancerous tumors. It can be the only treatment used for a condition. Or proton therapy may be used along with other treatments, such as surgery and chemotherapy.

Proton therapy also may be used if cancer remains or comes back after traditional X-ray radiation therapy.

Proton therapy sometimes is used to treat:

• Brain tumors.
• Breast cancer.
• Cancer in children.
• Esophageal cancer.
• Eye melanoma.
• Head and neck cancers.
• Liver cancer.
• Lung cancer.
• Lymphoma.
• Prostate cancer.
• Rectal cancer.
• Sarcoma.
• Skull base tumors.
• Spinal cord tumors.
• Spinal tumor and spinal mass.
• Vertebral tumors.

Clinical trials are studying proton therapy as a treatment for several other types of cancer.

Proton therapy may be particularly helpful for treating cancers and tumors near vital organs, such as the brain and spinal cord. It also may be helpful in conditions that affect children, as children's bodies are more sensitive to the effects of radiation.

Risks

Proton therapy side effects can happen as cancer cells die or when energy from the proton beam damages healthy tissue nearby.

Because healthcare professionals can better control where proton therapy releases its highest concentration of energy, it's believed to affect less healthy tissue. For some cancers, this may lead to fewer side effects than traditional radiation therapy. Still, proton therapy does release some of its energy in healthy tissue.

Risks and side effects may depend on which part of the body is treated and the dose of proton therapy that's given.

Common side effects of proton therapy include:

• Fatigue.
• Hair loss around the part of the body being treated.
• Skin changes around the part of the body being treated, including irritation, dryness, itching and peeling.
• Soreness around the part of the body being treated.

Proton therapy side effects often are similar to the side effects that can happen with traditional radiation therapy. But this may depend on the part of the body being treated. Proton therapy may be most helpful for treating cancer and tumors that grow near sensitive structures.

How you prepare

To prepare for proton therapy, discuss this treatment option with your healthcare professional. Your health professional can help you understand the possible benefits and risks of this treatment. Preparing for proton therapy may involve finding a proton therapy center, considering the cost and having a treatment planning session.

Find a proton therapy center

Proton therapy isn't widely available in the United States. To find a hospital that offers proton therapy, use online resources such as the National Association for Proton Therapy, which lists the locations of proton therapy centers in the United States. Ask your healthcare team if proton therapy is available in your area. Getting proton therapy may require traveling far from home, so consider this when deciding whether to have this treatment.

Consider the cost

Proton therapy sometimes costs more than traditional radiation therapy. In the United States, health insurance and Medicare may cover the cost of treatment for certain conditions. Talk with your healthcare team about the cost of treatment.

Have treatment planning

Before you are treated with proton therapy, your healthcare team guides you through a planning process to ensure that the proton beam reaches the right spot in your body.

Planning typically includes:

• Determining the best position for you during treatment. During a simulation of your radiation treatment, your radiation therapy team works to find a comfortable position for you during treatment. It's important that you lie still during treatment, so finding a comfortable position is vital.

  You'll be positioned on a table that will be used during your treatment. Cushions and body molds are used to place you in the correct position and to help you keep still. Your radiation therapy team will mark the area of your body that will receive the radiation. You may receive a temporary marker or permanent tattoos.

• Planning the path of the protons with imaging tests. You may have MRI or CT scans to find the area of your body that needs treatment and figure out how best to reach it with the proton beams.

What you can expect

During proton therapy, you lie on a table while a machine aims energy beams at your body.

Proton therapy often happens five days a week for several weeks. However, depending on your condition, you may have only one or a few treatments. The actual proton therapy treatment may take only a few minutes, but expect to spend 15 to 30 minutes preparing before each treatment session.

Before proton therapy

Before the proton therapy treatment, you may have imaging tests and blood tests to see if the dose you receive needs to be recalculated based on changes in weight, or tumor size and shape.

To prepare for treatment, you'll be positioned on a table. Cushions and body molds will be used to hold your body still. Then you'll have an imaging test, such as a CT scan, to make sure your body is in the same position before each treatment.

Your radiation therapy team then will leave the room and go to an area where team members can monitor you. They still can see and hear you.

During proton therapy

During proton therapy, a machine directs proton beams at precise points on your body. You'll hear the machine when it's turned on and delivering the dose of proton therapy. However, you won't be able to feel the radiation during your treatment.

A proton therapy machine is a complex system designed to deliver radiation precisely. It starts with a particle accelerator that generates high-energy protons. These protons are then guided through a beamline, which brings the proton beam to a machine in the treatment room. This machine is called a gantry. The gantry can move around the treatment table, aiming the proton beam at your body from many different angles.

There are different kinds of proton therapy machines that shape and direct the proton beams in different ways. They all direct proton beams precisely with the goal of hurting cancer and tumors, while sparing the nearby healthy tissue as much as possible.

After proton therapy

Once your treatment session is complete, you can go about your day. You won't be radioactive or give off radiation.

Side effects of proton therapy usually develop over time. You may experience few side effects at first. But after several treatments you may experience fatigue. This can make it feel like you have little energy or your usual activities take more energy. You also may notice a skin reaction similar to a sunburn in the area where the proton beams are directed.

Results

Ask your healthcare team when you can expect to know the results of your proton therapy treatment. Your care team may recommend periodic imaging tests during and after your proton therapy to determine whether your condition is responding to the treatments.