Radiation therapy has an important role in treating all stages of breast cancer because it is so effective and relatively safe. It may be appropriate for people with stage 0 through stage III breast cancer after lumpectomy or mastectomy. Radiation can also be very helpful to people with stage IV cancer that has spread to other parts of the body.
Women who are pregnant should not have radiation. Radiation is never safe during pregnancy. Visit the Treatment for Breast Cancer During Pregnancy page for more information.
Radiation therapy is recommended to most people who have lumpectomy (lumpectomy plus radiation is sometimes called breast-preservation surgery). Radiation attempts to destroy any cancer cells that may have been left in the breast after the tumor was removed.
Typically a doctor will recommend lumpectomy followed by whole breast radiation if the cancer is:
- early stage
- 4 centimeters or smaller
- located in one site
- removed with clear margins
Radiation therapy may be recommended after mastectomy to destroy any breast calls that may remain at the mastectomy site. During breast removal, it's difficult to take out every cell of breast tissue, especially the tissue behind the skin in front of the breast or back along the muscle behind the breast. Usually any leftover breast cells are normal. But because it's possible for some breast cancer cells to linger, there is a risk of recurrence in the area where the breast was. Based on your pathology report, your doctor may recommend radiation therapy if you’ve had a mastectomy.
These factors are associated with a high risk of recurrence after mastectomy. Radiation may be recommended if any of these factors are present:
- The cancer is 5 centimeters or larger (the cancer can be one lump, a series of lumps, or even microscopic lumps that together are 5 centimeters or larger).
- The cancer had invaded the lymph channels and blood vessels in the breast.
- The removed tissue has a positive margin of resection.
- One or more lymph nodes were involved.
- The cancer has invaded the skin (with locally advanced or inflammatory breast cancer).
Based on these risk of recurrence factors, about 20% to 30% of people are considered at high risk of recurrence after mastectomy. Radiation would be recommended to help reduce this risk by up to 70% (for example, a 30% risk may be reduced to just under 10%). Treatment is given to the area where the breast used to be and sometimes to the lymph node regions nearby.
Some people have a moderate risk of recurrence. They're in the "gray zone" because the cancer has characteristics that increase their risk, but not to a point where the risk is considered high. For example, you might have a 4 centimeter cancer. You and your doctor need to carefully consider your unique situation. Some people in the gray zone want to know they have done everything reasonable to treat the cancer, to avoid or reduce the risk of ever having to deal with it again. Others in the gray zone may decide not to go through with radiation therapy after a discussion with their doctors.
When radiation is NOT an option
Radiation is not an option for you if:
- you have already had radiation to that area of the body
- you have a connective tissue disease, such as scleroderma or vasculitis, which makes you extra-sensitive to the side effects of radiation
- you are pregnant
- you are not willing to commit to the daily schedule of radiation therapy, or distance makes it impossible
Can radiation therapy be repeated to the same area again?
Full-dose radiation is usually given only once to a particular part of the body. Your normal tissues can safely tolerate a limited amount of radiation. Your radiation oncologist knows how to pick the right dose of radiation to accomplish two things:
- reach the maximum therapeutic dose — the amount that's likely to destroy cancer cells
- avoid or minimize side effects to the normal tissue
After radiation is over, the normal tissues heal and get back to normal. But because you have received about as much radiation as your healthy cells can safely handle, it is not possible to treat this area again with another full dose of radiation. If cancer returns to the same breast area, depending on the radiation dose you already received, you may or may not be able to receive a limited amount of additional radiation treatment in that same area. Your doctor will know what the limits are, and together you can decide if this is a good treatment option for you.
It's important to note that this information refers to treating the SAME part of the body a second time. If cancer should occur elsewhere in your body (including the other breast), radiation can be used to its full effect.
The timing of radiation
The sequence and timing of radiation treatment depends on your individual situation. Radiation may be given immediately after surgery or after other forms of treatment. Here are some examples of various treatment sequences that involve radiation:
- surgery → radiation → possible hormonal therapy
- surgery → chemotherapy → radiation → possible hormonal therapy
- chemotherapy, targeted therapy, or hormonal therapy → surgery → radiation → possible hormonal therapy
You may be wondering in what order you'll have treatments and how your doctors decide which one comes first, second, etc. In general, when it's part of your treatment plan, chemotherapy is usually given first after surgery. Radiation then follows chemotherapy — it's not usually given at the same time. Depending on what chemotherapy you’re taking, there can be anywhere from 2 weeks to a month between the last chemotherapy dose and the start of radiation. For example, the wait is about:
- 1 month between the last dose of an anthracycline-type chemotherapy (Adriamycin [chemical name: doxorubicin], Ellence [chemical name: epirubicin]) and the start of radiation
- 2 to 3 weeks between the last dose of a taxane (Taxol [chemical name: paclitaxel], Taxotere [chemical name: docetaxel], or Abraxane [chemical name: albumin-bound or nab-paclitaxel]) and the start of radiation
When chemotherapy is not part of your treatment plan, radiation is usually given soon after surgery. The timing depends on the type of radiation you'll be receiving:
- External beam radiation, the most common type, usually starts about 3 to 6 weeks after surgery.
- Partial-breast radiation is usually given immediately after surgery.
- Intraoperative radiation is given in the operating room during surgery, just after the cancer tissue has been removed but before the opening in the skin has been closed.
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