Radiation Therapy for Thymus Cancer

Radiation therapy is a treatment that uses high-energy radiation in the form of x-rays or radioactive particles to kill cancer cells.

When is radiation therapy used for thymus tumors?

Radiation therapy can be used in many ways to treat thymus tumors (thymomas and thymic carcinomas):

• It is often used after surgery if the doctor thinks that some cancer was left behind.
• Even when no visible tumor was left after surgery, radiation therapy is sometimes given to try to kill any small areas of cancer that might have been left behind because they were too small to see. This is called adjuvant therapy. It is most often given to people with stage III or IV thymomas or thymic carcinoma.
• Some people who can’t have surgery might get radiation therapy alone. Sometimes chemotherapy is given with radiation to help it work better.
• For people with advanced disease, radiation therapy can sometimes help ease symptoms from the cancer such as shortness of breath, pain, bleeding, or trouble swallowing.

How is radiation therapy given?

The type of radiation therapy used most often to treat thymic cancer is external beam radiation therapy (EBRT). This type of radiation therapy uses x-rays from a machine outside the person’s body to kill cancer cells.

Radiation is an important part of treatment for some thymus tumors, especially when they can't be removed completely with surgery. The thymus sits in the front of the chest close to many delicate and important structures. Radiation beams need to be aimed carefully to avoid damaging the tissue around the thymus. To help with this precision, doctors often use advanced forms of EBRT, such as 3D conformal radiation therapy (3D-CRT) and intensity-modulated radiation therapy (IMRT). Some cancer centers may also offer newer forms of radiation therapy, including:

• Image-guided radiation therapy (IGRT): An imaging test is done to create pictures of the thymus right before each treatment. Since the thymus's position in the body can shift slightly from day to day, IGRT helps make sure the radiation is aimed as precisely as possible.
• Motion management techniques: These help adjust for body movements during treatment, such as breathing, which can shift the area that needs to be treated.
• Proton beam therapy: This therapy uses protons instead of x-rays. Standard x-ray beams release energy as they pass through the body, which can damage healthy tissue along the way. Protons work differently. They pass through the body without affecting most of the tissue. Protons release most of their energy only after traveling a set distance, which is programmed to be at the tumor. This means more radiation reaches the tumor and less reaches the healthy tissue around it.

Before treatment begins, your care team will take careful measurements to determine the right angles and dose to precisely aim the radiation. They often use special CT scans to help plan everything in advance.

Treatment itself feels much like getting an x-ray, just more intense. It doesn't hurt, though it can cause side effects. Each radiation session usually lasts only a few minutes. Most of the appointment time is spent making sure you are positioned correctly. Radiation is typically given five days a week for several weeks.

What are side effects of radiation therapy?

Common side effects of radiation therapy include:

• Fatigue
• Skin changes where the radiation passes through, such as redness and blistering
• Nausea and vomiting
• Irritation of the esophagus (the swallowing tube), which could cause painful swallowing and eating problems
• Poor appetite and weight loss
• Diarrhea if the abdomen or pelvis is treated

Radiation can damage bone marrow, leading to low blood counts. This can lead to anemia (low red blood cell counts), which can make people feel weak and tired. It can also lead to low white blood cell counts, which increases the risk of serious infections.

Radiation therapy to the chest can also damage the lungs. Damage can lead to trouble breathing and shortness of breath. It usually gets better after radiation treatments stop, but sometimes the damage is long-term.

Most side effects only last a short time and get better after radiation treatment is done.

If radiation therapy is given along with chemotherapy, the side effects are often worse.

If you are having any side effects from radiation therapy, tell your doctor or nurse. There are often ways to help control these symptoms.

More information about radiation therapy

To learn more about how radiation is used to treat cancer, see Radiation Therapy.

To learn about some of the side effects listed here and how to manage them, see Managing Cancer-related Side Effects.