The Who, What, Where, When and Sometimes, Why.

Going Through Radiation Therapy

Radiation therapy can harm normal tissue, so it’s carefully planned and precisely delivered. This helps make sure the radiation kills as many cancer cells as it can while doing as little harm as possible to other parts of your body.

Radiation therapy is planned specifically for your breast cancer, the shape of your body and your internal anatomy. This is why sessions can’t be split between different treatment centers.

Your treatment plan is based on:

  • The tumor size, type and location
  • The number of lymph nodes with cancer
  • The type of breast surgery (and lymph node surgery) you had
  • The shape of your breast or chest wall, and the shape and location of nearby organs (such as your heart and lungs)

Planning session

Your radiation oncologist oversees the radiation planning session (also called a simulation).

You will lie on a special table while your radiation oncologist decides the proper dose of radiation and where to give the radiation.

Your radiation oncologist will use a CT scan or an MRI to guide the radiation planning. This allows the radiation oncologist and their team to tailor the radiation fields to your body shape and anatomy, as well as to the details of the tumor. They will determine the correct position for your body to be in when you get radiation therapy.

During the planning session, your radiation oncologist may put small marks (about the size of a pinhead) on your skin. These marks make sure you’re correctly positioned for each treatment. Some centers use very small permanent tattoos. Other centers use temporary marks, so it’s important not to wash these marks off until you finish all your radiation therapy. Still other centers have moved away from putting any visible marks on the skin.

You may be asked to hold your breath for a few seconds at certain times during the planning session. This is one way to minimize radiation exposure to the heart.

Radiation therapy sessions

Your radiation oncologist leads a team of radiation technologists and nurses. The team will work with you at each radiation therapy session.

What should I expect?

During each session, you will lie on a special table.

You may be asked to hold your breath while the radiation is given. This is one way to minimize radiation exposure to the heart.

Each session lasts about 10 to 20 minutes. Most of this time is spent positioning your body to make sure the treatment is given exactly as planned.

You will not be radioactive

You will not be radioactive when you leave the radiation treatment center after any standard radiation therapy session. You will not pose any radiation risk to your family or your pets.

However, it’s important not to become pregnant during radiation therapy, as radiation can harm the fetus.

How often will I go for treatment?

Your schedule of radiation sessions is designed to treat your breast cancer. So, schedules vary from person to person. Your radiation oncologist will go over your schedule with you.

Treatment is most often given once a day, 5 days a week, for 1-6 weeks.

After a lumpectomy, many women get hypofractionated whole-breast radiation therapy which uses a slightly higher dose of radiation per session. This reduces the number of treatment sessions and shortens the overall course to 5 days a week, for 1-4 weeks. Sometimes radiation therapy is given once a week for several weeks in a row.

Hypofractionated radiation therapy is under study for use after a mastectomy.

Learn more about emerging areas in radiation therapy.

Radiation boost

After radiation therapy to the whole breast, you may get more radiation to the tumor bed (the part of the breast that had the tumor). This is called a boost. It’s usually 2-4 extra days of treatment.

A boost increases the amount of radiation given to the tumor bed. This is the area at highest risk for breast cancer recurrence.

Your boost radiation session is similar to a regular radiation therapy session.

Partial breast radiation therapy after a lumpectomy

Radiation therapy often delivers radiation to the whole breast. Partial breast radiation therapy delivers radiation only to the area around the tumor bed (the space where the tumor was removed during a lumpectomy). Partial breast radiation therapy is also called partial breast irradiation.

It’s most often done in a shortened course over 3-10 days. This reduces the number of treatment sessions. It may also be completed in 3-4 weeks, similar to whole breast radiation therapy.

Partial breast radiation therapy is a treatment option for some people with early-stage breast cancer [10].

Talk with your radiation oncologist about whether you might be a good candidate for partial breast radiation therapy. Discuss the pros and cons of partial breast radiation therapy compared to whole breast radiation therapy.

Methods of partial breast radiation therapy

Methods of partial breast radiation therapy include:

  • Brachytherapy uses targeted radiation placed inside the tumor bed. Implanted radiation “seeds” (interstitial radiation therapy) or a single small balloon device (intracavitary radiation therapy) can be used to deliver the radiation.
  • External beam radiation therapy uses standard external beam radiation therapy, but only targets the tumor bed and a small area of surrounding breast tissue.

When your treatment plan includes chemotherapy

Whole breast radiation therapy is usually given after chemotherapy. In contrast, sometimes partial breast radiation therapy may be given before chemotherapy.

Things to remember while going through radiation therapy

Things to remember

  • Don’t wash the ink marks off your skin.
  • Check with your radiation therapy team before putting any lotions or powders on the treated area.
  • Wear clothing that’s easy to take off in case you need to change into a hospital gown.
  • Use reliable birth control to prevent pregnancy (radiation can harm a fetus). Discuss the best form of birth control with your health care team.
  • Keep the treated area out of the sun.
  • Don’t put anything very hot or very cold (such as a heating pad or an ice pack) on the treated area.
  • Tell your health care team about any side effects.

Adapted from National Cancer Institute materials [12].

Transportation, lodging, childcare and eldercare assistance

Getting to and from the treatment center every day for weeks can be hard, especially if you live far away or if others rely on you for care. It’s OK to ask for help. It’s important to complete your radiation therapy without gaps or delays.

There may be resources available if you need a ride to and from radiation therapy or help with childcare or eldercare. Family and friends often want to help but don’t know how. These are great ways for them to get involved.

There may be some programs that help with local or long-distance transportation and lodging (if you need a place to stay overnight during treatment).

There may also be programs to help you with childcare or eldercare costs.

Learn more about transportation, lodging, childcare and eldercare assistance programs.

Find other resources that offer social support and practical support.

Komen Financial Assistance Program

Susan G. Komen® created the Komen Financial Assistance Program to help those struggling with the costs of breast cancer treatment by providing financial assistance to eligible individuals.

To learn more about this program and other helpful resources, call the Komen Breast Care Helpline at 1-877 GO KOMEN (1-877-465-6636) or email

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Susan G. Komen® Support Resources

  • Do you need help? We’re here for you. The Komen Patient Care Center is your trusted, go-to source for timely, accurate breast health and breast cancer information, services and resources. Our navigators offer free, personalized support to patients, caregivers and family members, including education, emotional support, financial assistance, help accessing care and more. Get connected to a Komen navigator by contacting the Breast Care Helpline at 1-877-465-6636 or email to get started. All calls are answered Monday through Thursday, 9 a.m to 7 p.m. ET and Friday, 9 a.m. to 6 p.m. ET. Se habla español.
  • The Komen Breast Cancer and Komen Metastatic (Stage IV) Breast Cancer Facebook groups are places where those with breast cancer and their family and friends can talk with others for friendship and support.
  • Our fact sheets, booklets and other education materials offer additional information.


Updated 04/11/24



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