Radiation therapy after lumpectomy or breast-conserving surgery (BCS) is generally administered to the entire breast, regardless of the cancer location. Partial breast irradiation (PBI) is a method of administering radiation therapy that treats only the part of the breast from which the cancer was removed—the part at greatest risk of recurrence.

What is the Purpose of PBI?

The purpose of PBI is to reduce the risk of cancer recurrence while also limiting the side effects of radiation on the remaining breast. PBI also reduces the overall treatment time. Traditional whole-breast radiation therapy is typically administered as a 3- to 6-week course of daily radiation treatment. PBI is generally administered in only 5 days, beginning after recovering from surgery. The exception is intraoperative radiotherapy, which is administered as a single treatment entirely during surgery at the time of lumpectomy.

How is PBI Administered?

There are 4 commonly used techniques for administering PBI:

• Single-entry intracavitary catheter-based techniques (such as, Mammosite®, Contoura®, and SAVI® devices) require insertion of the PBI device into the cavity created by removal of the cancer.
• Multicatheter interstitial brachytherapy involves placement of 15-20 catheters through the breast, surrounding the surgical cavity. In each of the catheter-based approaches, radiation is administered using a radioactive seed briefly inserted into each catheter twice a day for 5 days.
• 3D-conformal radiation does not require placement of catheters, but utilizes radiation that is passed through the skin of the breast, similar to having an X-ray performed.  3D-conformal radiation therapy is administered in twice daily treatments for 5 days.
• IORT (Intraoperative Radiation Therapy) uses a device that is inserted into the surgical cavity at the time of lumpectomy. The radiation therapy is delivered in the Operating Room. When the radiation treatment is completed, the device is removed before the wound is closed.

Who is Appropriate for PBI?

PBI is generally considered appropriate for patients age 40 and older with smaller tumors (less than 3 cm), negative lymph nodes, and a desire to be treated with lumpectomy.

What are the Advantages and  Disadvantages of PBI?

The main advantages of PBI are the convenience of receiving breast radiotherapy over a shorter time period of time (5 days or less), and the ability to limit the side effects of radiation to the part of the breast most at risk of a recurrence.

The main disadvantage of PBI is that there are no long-term (meaning >10 years) studies comparing its effectiveness and safety to traditional whole breast radiotherapy. However, short-term results show similar effectiveness and safety. PBI is also not appropriate for patients with larger tumors, more extensive breast cancers, and for women that require radiation after mastectomy.