The majority of patients with early stage breast cancers choose breast conserving treatments for their breast cancer. This involves removing the tumor through a procedure called a “lumpectomy.” In order to reduce the risk of recurrence within the breast, radiation therapy is often recommended to be delivered either to the entire breast or to the lumpectomy cavity.
In this video, Dr. Lawenda discusses a technology called accelerated partial breast irradiation (“APBI”.) APBI is one of the most convenient radiation therapy approaches in the management of breast cancer, as it takes only 5-days to deliver the entire course of treatment. Most radiation therapy treatments for breast cancer require a significantly longer course, often 3-to-7 weeks of daily treatment.
APBI can be delivered with either a radiation isotope based technology (such as the catheter systems demonstrated in the video) or with external beam irradiation (although some studies indicate that the cosmetic outcomes may not be as good with external beam radiation.) Intra-operative radiation can also be used at centers that offer this technique (although the long-term data on this approach are limited.)
Who Needs Radiation Therapy After Lumpectomy?
The NCCN guidelines (an academic breast cancer expert consensus panel) indicate that all patients treated with a lumpectomy should also be offered radiation therapy to reduce the risk of recurrence. There are caveats to this, as some patients are at sufficiently low-risk of recurrence after surgery that the benefit of adding radiation therapy may be very small. This requires a nuanced conversation with your radiation oncologist to assess your individual risk.
Who Is A Good Candidate For Accelerated Partial Breast Irradiation (APBI)?
Studies of APBI inform us that the rates of local control in selected patients with early-stage breast cancer may be comparable to those treated with standard whole breast radiation therapy.
Suitable candidates for APBI include (The American Brachytherapy Society consensus statement 2017):
- 45 years or older
- All invasive histologies and DCIS
- Tumors 3 cm or less in size
- Negative lymph nodes
- No lymphovascular space invasion
- Negative margins (widths of ≥2mm)
- ER-positive or negative
- BRCA negative
- Intraoperative radiation therapy (IORT) and electronic brachytherapy should not be offered regardless of technique outside of clinical trial
ASTRO 2017 APBI Guidelines (see the table, below):
The “suitability” row (top row) indicates which patients can be recommended to receive APBI outside of a clinical trial setting. The “update” column (on the right) shows us the current indications that meet this criteria for treatment. Intraoperative radiation therapy (IORT) is an APBI option for patients who meet the criteria for this group. Patients in the “cautionary” (bottom row) can still receive APBI, but IORT is not recommended. Patients in the “unsuitable” row should not be offered APBI.
APBI Radiates Significantly Less Normal Tissue Than Whole Breast Radiation
The image below (upper left: “whole breast radiation”) shows the typical external beam radiation therapy field, which treats a tangential volume of breast tissues, chest wall and small portion of the underlying lung. The image below (upper right: partial breast irradiation), is an example of using an external beam approach to treat the lumpectomy cavity (the red lined volume.) The high-dose volumes in the two treatment techniques illustrate the marked difference in amount of tissues treated to this dose. The device in the photo at the bottom is called a “SAVI” brachytherapy catheter, which is used for partial breast irradiation. Brachytherapy catheters deliver the least amount of radiation to the normal tissues away from the lumpectomy cavity, which is why this technique is preferred over external beam techniques whenever feasible.
