Radiation Therapy for Breast Cancer: What Patients Should Know
Breast cancer is not a single disease. It includes multiple subtypes, defined by the presence or absence of certain receptors such as estrogen (ER), progesterone (PR), and HER2. Because each subtype behaves differently, treatment plans are personalized. A multidisciplinary cancer care team works together to select the most appropriate approach for each patient, which may include radiation therapy.
What is radiation therapy?
Radiation therapy is a common cancer treatment that uses high-energy X-rays to target cancer cells. The experience is similar to undergoing imaging tests like a CT scan. Radiation damages the DNA of cancer cells, preventing them from reproducing. Healthy cells are better able to repair this damage, which helps limit harm to normal tissue.
Radiation can be delivered in two main ways:
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External beam radiation therapy, where radiation comes from a machine outside the body
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Brachytherapy, where a radioactive source is placed inside the body near the tumor
Most patients with cancer will receive radiation therapy at some point during their treatment.
Radiation therapy options for breast cancer
Radiation therapy is frequently part of breast cancer treatment because it can be carefully customized. Before treatment begins, patients meet with a radiation oncologist for detailed imaging and 3D planning of the chest. This allows the care team to design a plan that treats the cancer effectively while minimizing exposure to nearby organs such as the heart and lungs.
Depending on the individual case, treatment may involve:
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Whole breast radiation
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Partial breast radiation
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Regional lymph node irradiation
Special considerations for left-sided breast cancer
When breast cancer affects the left breast, extra care is taken to protect the heart. One commonly used technique is deep inspiration breath hold (DIBH). By taking and holding a deep breath during treatment, the lungs expand and increase the distance between the heart and the breast, reducing radiation exposure to the heart. This method has significantly lowered the risk of radiation-related heart damage.
Another advanced approach is intensity-modulated radiation therapy (IMRT). This technology adjusts the strength of radiation beams to better protect healthy tissues while delivering effective doses to cancer cells. IMRT is used in breast cancer as well as many other cancer types.
When is radiation therapy used?
Radiation therapy is often recommended after surgery to eliminate microscopic cancer cells that may remain. It may be used:
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After a lumpectomy, targeting the surrounding breast tissue
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After a mastectomy, especially if cancer involvement of lymph nodes or nearby structures is suspected
Radiation therapy may also be used when surgery is not an option.
How long does treatment last?
Most radiation therapy sessions last about 15 minutes and are typically given five days per week over one to six weeks. Treatment length depends on the individual patient and cancer characteristics.
Some patients with early-stage, low-risk breast cancer may qualify for shorter treatment schedules, such as:
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Accelerated partial breast radiation (Florence protocol)
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FAST-Forward protocol, which delivers whole breast radiation over one to two weeks
These options are not suitable for everyone but are used when clinically appropriate.
Possible side effects
Short-term side effects may include:
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Breast swelling
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Skin redness or peeling (similar to sunburn)
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Fatigue
These usually improve within a few months after treatment.
Long-term side effects are less common and may include:
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Changes in breast size or appearance
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Skin texture changes
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Discomfort in the treated area
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Lymphedema, nerve irritation, or lung inflammation (rare)
Your radiation oncologist will review potential side effects specific to your treatment plan and answer any questions you may have.
The importance of early detection
Advances in breast cancer treatment—including radiation technology—have greatly improved outcomes. However, early detection remains the most important factor in successful treatment. Routine mammograms are still the most effective way to detect breast cancer early, often before symptoms appear.
Women should discuss their personal risk factors and family history with their healthcare provider. Current guidelines generally recommend starting screening at age 40, with individualized screening schedules thereafter.