Case Study

Case report: CyberKnife for breast cancer

By Sandra Vermeulen, M.D.

Radiation Oncologist
Co-Director, Seattle CyberKnife Center

Amy is a 44-year-old female who had a screening mammogram in March that showed a new density in the upper outer quadrant of her left breast. An MRI confirmed this lesion to be the only suspicious mass in either breast. An ultrasound core biopsy was consistent with an infiltrating ductal carcinoma.


In April the patient underwent a partial mastectomy and left axillary sentinel node dissection. Final pathology revealed a 0.8-centimeter, high-grade tumor with a Bloom-Richardson score of 8/9. No vascular/lymphatic space invasion was identified. Minimal ductal carcinoma in situ of high nuclear grade without necrosis was present. Surgical margins were free of both the invasive and noninvasive disease components. The infiltrating tumor was ER/PR negative and HER2/Neu 2+ positive for over expression. There was no evidence of disease metastases (cancer cells appearing in another area) in the two sentinel lymph nodes that were removed.

I met Amy to discuss radiation options for local disease control shortly after her surgery while she was still undecided about chemotherapy.

I explained the current standard of care, which includes 6 weeks of daily radiation to the involved breast, as well as the accepted risks of side effects. In response, Amy explained she wanted cutting-edge treatments that promised high local control with reduced risk.

I also told her about using a linear accelerator for 3D-conformal external beam radiation therapy and that it would require a 25-millimeter volume (area receiving radiation) to ensure accurate coverage of the 10-millimeter volume (the area where the cancer was removed, plus some surrounding tissue). This extra volume covers day-to-day variations in set up and corrects for target motion due to breathing during treatment.

In addition, I also explained that CyberKnife treatment of early-stage breast cancer patients was a very new treatment option - in fact she would be one of the first three breast-cancer patients treated in the United States with CyberKnife. With 1-mm accuracy, the treatment volume could be reduced from 25 millimeters to about 12-13 millimeters. Reducing the volume would decrease the risk of side effects by reducing radiation coverage of normal tissue within the high-dose volume.

I explained to Amy that we had written a treatment protocol that had been peer approved by the CyberKnife Society, but we had not yet performed this treatment.

Amy decided on CyberKnife treatment.

Radiation treatment

For one week in June, Amy received CyberKnife treatment to her partial breast at the Seattle CyberKnife Center at Swedish Medical Center. Treatments that were approximately 60 minutes long were delivered once a day for five consecutive days. She felt great during and immediately after treatment and experienced no side effects. She was able to resume her normal activities after each treatment.

I saw Amy in follow up one month after treatment. She had experienced no skin changes or lymphedema. She was very happy with her decision to be treated with the CyberKnife.

Read more about Amy's story.

Read Amy's story and case report in PDF.


  • Bloom-Richardson score: A number that is arrived at by analyzing various characteristics of a tumor. This score helps doctors determine the best treatment.
  • Carcinoma: A harmful, fast-growing tumor of tissue covering internal organs and surfaces Infiltrating ductal carcinoma: One of the most common types of breast cancer, which begins in the ducts of the breast, and then invades and replaces normal breast tissue
  • Lymph node(s): Sponge-like tissue that filters lymphatic fluid (fluid that transports white blood cells) and stores white blood cells to help the body fight infection
  • Lymphedema: Swelling caused by lymph (fluid containing white blood cells) collecting in the tissue
    Malignant tumor: A cancerous tumor that can growth into and destroy nearby tissue or spread to other parts of the body
  • In situ tumor: A tumor that has not spread to other tissue or parts of the body. Mammogram: An X-ray of the soft tissue of the breast.
  • Metastases: Cancer cells have spread to other parts of the body from the original site.
  • MRI: An abbreviation for magnetic resonance imaging. An MRI uses magnetic signals, rather than X-rays, to create higher resolution images
  • Necrosis: Death of cells
  • Sentinel lymph node(s): The lymph node(s) closest to a tumor.
  • Ultrasound: High-frequency sound waves are used to create high definition images of internal tissues and structures