Radiation therapy works by directing strong beams of X-rays or other particles at tumors. This destroys cancer cells. This is a type of local cancer treatment. A radiation oncologist will create a treatment plan for you. Each person's plan is different. Your plan will include the type of radiation you'll get, and the dose. It will also include how often and for how long you'll get treatment.

Radiation can help treat stomach cancer:

• Before surgery to shrink the cancer. This may help to make the surgery easier.
• After surgery to destroy any cancer cells that remain. This can help keep the cancer from coming back.
• As palliative (supportive) therapy to shrink tumors and ease symptoms caused by the cancer. While this doesn't cure the cancer, it can help reduce pain, bleeding, or trouble eating.

When radiation is used to treat stomach cancer, it's often given along with chemotherapy. This is called chemoradiation.

Radiation therapy damages normal cells as well as cancer cells. This can cause side effects. The side effects depend on the amount and type of radiation. They may start during treatment. And they may happen in the weeks or even months after it. Side effects may get worse as treatment goes on. They also tend to be worse if radiation and chemo are given at the same time.

They may include:

• Skin irritation over the treatment area (it may blister and peel like a bad sunburn)
• Upset stomach (nausea) or vomiting
• Diarrhea or stomach cramping
• Heartburn-like pain
• Trouble eating
• Tiredness
• Low blood cell counts

Talk with your healthcare team about any changes you notice or side effects you have. Ask them what problems you should watch for and when you need to call them. Most side effects can be treated or kept from getting worse. Side effects tend to get better over time after treatment ends and your body heals. But some side effects may last for longer.

The type of radiation most often used to treat stomach cancer is called external beam radiation therapy (EBRT). For EBRT, a large machine sends beams of radiation into your body. It's a lot like getting an X-ray, but it takes longer.

There are 2 other methods of giving EBRT:

• 3-D conformal radiation therapy. This type aims radiation from several directions and the beams follow the shape of the tumor. The beams of radiation are the same intensity. This can lessen the damage to nearby healthy tissue.
• Intensity-modulated radiation therapy (IMRT). IMRT uses a computer to send certain doses (intensities) of radiation precisely to certain parts of the tumor. It also can reduce the damage to nearby healthy tissue.

Before your first treatment, you'll have an appointment to plan for it. This is called simulation. During this appointment:

• A CT scan or MRI or other imaging tests might be used to map out exactly where the tumor is in your body.
• You'll lie on a table while the radiation team uses a machine to plan where the radiation will be aimed. The therapist may mark your skin with tiny dots of permanent ink or tattoos. These are used to be sure that the radiation is aimed at the exact same place each time.
• A plastic mold or cast of your body may be made. The mold helps you get in the same position for each treatment and keeps you from moving while treatment is given.

You'll get radiation every day at a hospital or clinic. You'll likely get treatment 5 days a week for a few weeks or months. The length of time depends on the type and dose of radiation.

Each treatment lasts only a few minutes. It's a lot like getting an X-ray. The machine doesn't touch you during treatment, and treatment doesn't hurt. You may see lights from the machine that are lined up with the marks on your skin. This helps the therapist know you're in the right position. The therapist will leave the room while the machine sends radiation to your tumor. During this time, the therapist can see you, hear you, and talk to you. When the machine sends radiation to your tumor, you'll need to be very still. But you don't have to hold your breath.

Your radiation oncologist or nurse can tell you what to expect during and after treatment. Ask any questions so you know what to expect. Know how to contact your healthcare provider with any unexpected side effects or questions, including after clinic hours, during weekends, and holidays.