Radiation Therapy

Radiation therapy is a highly targeted, highly effective way to destroy cancer cells in the breast that may remain after surgery. Radiation therapy uses high-energy radiation to kill cancer cells by damaging their DNA. Radiation therapy has an important role in treating all stages of breast cancer because it is so effective and relatively safe. It can be used at the site of the original cancer or in areas where the cancer has spread. Radiation therapy preferentially kills cancer cells, but it can also affect normal cells. Therefore, treatment must be carefully planned to minimize side effects.

The radiation used for cancer treatment may come from a machine outside the body, or it may come from radioactive material placed in the body near cancer cells.


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Watch our breast cancer webinars to learn about screenings, treatment options, oncoplastic surgery, IORT, and much more! Funding for these educational webinars is generously provided by the Ken Johnson Family in memory of Joan Brierton Johnson.

Types of Radiation offered at Providence Saint John’s Health Center

In the Vasek Polak Radiation Oncology Department, our patients have access to the latest in radiation therapy technology.

External beam radiation is the most common type of radiation, typically given after lumpectomy and sometimes after mastectomy. Typically, radiation therapy is done with high energy x-rays or photons for the majority of the treatment. The radiation beam comes from a machine called a linear accelerator. Our Trilogy™ linear accelerator allows patients to receive higher-dose radiation treatments precisely targeted to the cancer in shorter sessions. This keeps our patients more comfortable, spares healthy tissue and may even improve a person’s overall outcome. The radiation beam is painless and non-invasive, and treatment itself lasts only a few minutes.

Before any radiation is delivered, patients first undergo a planning session, called a simulation, which includes a CT scan (3-dimensional x-ray) of the body in the exact same position as treatment will be given. This allows the radiation oncologist and physicist to generate a customized radiation treatment plan, ensuring optimal treatment of the target tissues and avoidance of normal tissues.

The full course of treatment is usually delivered over three to six weeks. When there is a reason to focus the radiation where the cancer was removed, sometimes an additional “boost” dose will be given for a week or two, often using electrons instead of photons to treat with a less penetrating, more focused beam.

After breast conserving surgery (lumpectomy), the usual course of radiation treats only the breast, although in some cases, there may be a recommendation to have nearby lymph node areas treated at the same time.

After a mastectomy, radiation therapy for the chest wall and nearby lymph node areas may be suggested. Whether or not radiation therapy should be used after mastectomy depends on several factors, including the number of lymph nodes involved, the tumor size, and whether or not cancer cells were found near the edge of the tissue that was removed. For patients who have undergone immediate reconstruction after mastectomy and require radiation treatment, our multidisciplinary team works together to offer an integrated program of post-mastectomy radiation. This approach often results in excellent local control of the cancer as well as a low rate of radiation-related problems with reconstruction.

A relatively new type of radiation to treat breast cancer is intraoperative radiation therapy (IORT). IORT is a highly targeted treatment, delivering a dose of radiation only to the “bed” of the breast cancer at the time of surgery. This allows maximal sparing of normal tissues. Results of clinical trials have demonstrated very low side effects, and very promising results. However, since follow-up time is relatively short, we are currently offering this treatment to carefully selected patients.

IORT is given during breast conserving surgery, while under anesthesia, immediately after the cancer has been removed.

An applicator for radiation is placed by the surgeon. The radiation oncology team then comes to the operating room to deliver the single treatment. Once the radiation has been delivered, the applicator is removed by the surgeon and nothing is left in the breast. The surgeon will then complete the operation. If on final pathology the cancer cells are found to have more worrisome features, then additional radiation will be given after surgery. Because of the inability to predict the extent of disease before surgery, studies have shown that approximately 25-30% of patients who receive IORT may need additional radiation therapy.

Accelerated partial breast irradiation (APBI) is an option for some patients after a lumpectomy. This treats a rim of normal breast tissue surrounding the surgical cavity, rather than the whole breast. The dose of radiation delivered with APBI is equivalent to a 5 week course of whole breast radiotherapy, but because a smaller volume is treated, the radiation can be delivered more quickly. Treatment is generally twice a day for 5 days, allowing the entire treatment course to be completed in one week. Because APBI has only been studied in patients with specific low-risk features, it is used more selectively than whole breast radiation. APBI at Providence Saint John’s Health Center is done using Intensity Modulated Radiotherapy (IMRT) External Beam Radiation Therapy or with High Dose Rate Brachytherapy (HDR) internal catheters/balloons.


Radiation treatments today are very precise, resulting in little harm to surrounding skin or underlying healthy tissues. Radiation is generally very well tolerated, but after approximately three weeks there may be some side effects, such as a sunburn-like condition on the skin, fatigue, discoloration of the skin, or swelling and heaviness in the breast.

Your Margie Petersen Breast Center Nurse Navigator, radiation oncology nurse, and physicians will provide education and details about your personalized care prior to you beginning treatment.

Learn More About our Vasek Polak Radiation Therapy Center

Webinar: Intraoperative Radiation Therapy for Breast Cancer – Sometimes Less Can Be Best

Watch our webinar to learn about intraoperative radiation therapy treatment for breast cancer from our experts at the Margie Petersen Breast Center at Providence Saint John’s.

Doctors and Specialists Who Treat Breast Cancer

The Margie Petersen Breast Center at Providence Saint John’s Health Center brings you some of the finest breast health and cancer care in Southern California.

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Margie Petersen Breast Team


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