Accelerated partial breast irradiation, or APBI, is a localized form of radiation treatment (brachytherapy) that involves the insertion of a radioactive "seed" to kill breast cancer cells that may remain after lumpectomy surgery. APBI delivers a highly effective dose of radiation while greatly reducing treatment time. This procedure requires close collaboration between the surgeon who removes the breast tumor, and the radiation oncologist who treats the tumor area after surgery.
Accelerated partial breast irradiation is performed about one to four weeks after a lumpectomy. A specialized catheter is inserted into the cavity left behind after removal of the tumor. The device remains in place during the course of APBI treatment, usually about 8-10 days.
There are currently three types of single-entry breast brachytherapy devices. Which one to use for the given patient is chosen by the surgeon and radiation oncologist based on the size and shape of the lumpectomy cavity. Each brachytherapy device is designed to hold the radioactive “seed” in designated positions within the device for defined lengths of time to insure radiation of the targeted breast tissue immediately surrounding the lumpectomy cavity:
- Strut Assisted Volume Implant (SAVITM): this device has 7-11 "struts" or catheters through which the iridium seed travels (see photo above). The struts are expanded after the device is inserted into the lumpectomy cavity.
- Mammosite®: a balloon is inserted into the lumpectomy cavity and inflated. The original Mammosite balloon had a single lumen (catheter). The Mammosite ML has four lumens through which the iridium seed travels.
- ConturaTM MLB: This is also a balloon device with five lumens (catheters) within the balloon through which the iridium seed travels. Contura also has vacuum ports on either end of the balloon, to remove air or fluid between the balloon and the targeted breast tissue.
During treatment, the iridium seed, about the size of a grain of rice, is inserted into the catheters (lumens). The seed is within the device in various dwell positions for a total of 5-10 minutes. The seed is withdrawn and then re-inserted six hours later, for a total of two treatments a day.
Who is eligible for APBI?
Partial breast irradiation is best for women who:
- Are 50 years of age or older
- Have small tumors of three centimeters or less that are confined to the breast
- Have clear margins
- Have no lymph nodes involved
Benefits of Accelerated Partial Breast Irradiation
When compared with standard radiation treatment, APBI offers several benefits:
- APBI is given twice a day over a period of 5-7 days, while external beam radiation treatment involves 5 treatments a week for 4-6 weeks
- The radiation dose is concentrated to the tissue surrounding the lumpectomy cavity, sparing normal tissue and critical organs such as the heart and lungs from unnecessary radiation
Since the introduction of accelerated partial breast irradiation in 2002, oncologists have been gathering data on cancer recurrence and survival rates in APBI patients. Although the data is still maturing, the results are encouraging, and accelerated partial breast irradiation is poised to become a standard treatment in the future for certain breast cancer patients.
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