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Radiation Therapy for Breast Cancer

Radiation therapy is recommended for most breast cancer patients, particularly those undergoing breast conservation therapy (BCT). Multiple clinical trials have demonstrated the equivalence of BCT compared to more radical surgery (mastectomy) in terms of both local tumor recurrence and survival. Consequently, BCT has become the treatment of choice for most breast cancer patients treated in the United States.

Radiotherapy is also commonly used after mastectomy, especially in patients with certain risk factors, including tumor involvement in regional lymph nodes. In these patients, radiation has been found to reduce the chance of a local recurrence and improve patient survival. For more about radiation therapy at UC San Diego Health, see Radiation Oncology.


Radiation therapy in women who undergo breast-conserving surgery may be delivered to the entire breast. Treatment often consists of two angled (tangential) beams designed to minimize dose to the underlying normal lung tissues. A similar approach may be used in women treated to the chest wall following mastectomy.

In women found to have lymph node involvement, radiation is also often delivered to the regional lymph nodes (axillary, supraclavicular regions and internal mammary nodes). In these women, additional radiation beams are matched to the tangential (breast) fields.

Whole breast irradiation is typically delivered in two phases with a high dose administered over three to five weeks, possibly followed by an additional “boost” delivered over five days to the lumpectomy cavity alone. Your physician will discuss if you are best suited to a three- to four-week course or a five- to six-week course.

Breast Radiation Image

An early-stage, right-sided breast cancer treated with two tangential radiation beams.

Breast Radiation Image

A breast cancer patient receives regional lymph node irradiation. The shoulder joint is shielded to minimize toxicity.

Partial Breast Irradiation (PBI)

PBI is another treatment option for early breast cancer. As the name implies, PBI involves irradiating only a portion of the breast (the lumpectomy cavity plus 1 to 1.5 centimeters of surrounding tissue) to attack remaining pre-cancerous cells that, if left untreated, may grow into a new tumor. Because a smaller volume of breast tissue is irradiated, treatment periods are significantly shorter, typically two to five days, but often treatment is twice a day.


A SAVI catheter in the breast (upper right hand corner) with colored concentric circles representing levels of radiation dose around the lumpectomy cavity.

For select patients, PBI has been shown to be comparable to whole breast irradiation.

The best candidates for PBI appear to be post-menopausal women with small tumors (less than 2 to 3 centimeters), negative resection margins, and no cancer cells in regional lymph nodes.

Other High Dose Rate Techniques

PBI is only one type of high dose rate (HDR) brachytherapy offered at UC San Diego Health.

Other HDR techniques that may a part of your treatment plan include: 

  • AccuBoost: A non-invasive, image-guided breast-conservation therapy that delivers a measured dose of radiation that matches the size, shape and location of the target site. This so-called "boost" dose is delivered directly to the tissue surrounding the surgical excision site. This machine can also be used for partial breast irradiation.
  • Strut Assisted Volume Implant (SAVI): A multi-channel catheter system. Each individual channel can be loaded with a brachytherapy source for varying lengths of time to better conform the dose to the shape of the lumpectomy cavity. Lower doses can be delivered to the overlying skin, chest wall, lung and heart. UC San Diego Health was the second center in the world to offer SAVI to patients. Patients typically receive treatment twice daily for two to five days.
  • Contura: A balloon catheter is inserted into the site of the lumpectomy and inflated with saltwater to snugly fit the excision cavity, improving radiation delivery to the site. Patients typically receive treatment twice daily for two to five days.
  • Mammosite: A multi-lumen balloon catheter with three offset lumen and one central lumen is placed within the lumpectomy cavity. The arrangement is designed to optimize dosimetric coverage, while minimizing radiation exposure to the skin and ribs. Patients typically receive treatment twice daily for two to five days.

Prone Breast Treatment

Typically, a breast cancer patient is treated in the supine position, lying face-up. UC San Diego Health also offers prone breast treatment, in which the patient is treated lying face-down with the breast hanging away from the body. This approach is used to direct radiation beams at an angle that spares healthy heart and lung tissue. Prone breast treatment is particularly valuable in large breasted individuals or individuals with a tumor on the left breast near the heart.

Deep Inspiration Breath-Hold

In this approach, the patient is asked to inhale and hold the air in the lungs to position the heart away from the radiation field. Deep inspiration breath-hold is standard practice but at UC San Diego Health, we use an advanced imaging system known as AlignRT to ensure that the patient's inhalations are consistent each time. 

Proton Therapy

Proton therapy is a type of radiosurgery that uses protons, instead of photons or electrons, to kill cancer cells. Because of the basic physics of protons vs. photons or x-rays, the approach may spare some normal tissues. It may also have lower long-term toxicity for patients with anatomy that makes photon treatment less desirable. Proton therapy, however, is a relatively new therapy and not widely available. Because of this, there is not yet the clinical data to support the expected theoretical benefits. When appropriate, UC San Diego physicians offer proton therapy for breast cancer patients at  California Protons Cancer Therapy Center, the only proton therapy center in the region.


More Information

Appointments & Referrals

Radiation Oncology Locations

La Jolla


Chula Vista

4S Ranch

  • 16918 Dove Canyon Rd, Ste 103

Patient Guide

Radiation Oncology Patient Handbook 

Radiation Oncology Patient Handbook Spanish 

Patient Education

Learn more about these topics at our Health Library: