Accelerated partial breast irradiation (APBI) is radiation therapy that is only given to the area of the breast that has the cancer. Like whole-breast irradiation, it is done to prevent recurrence by ensuring that any cancer cells that may remain in the tumor area are destroyed. However, accelerated partial breast irradiation delivers more radiation in a shorter treatment period, and it can be done either internally or externally, offering patients several benefits.

APBI is becoming a more common choice for women who’ve had a lumpectomy for early-stage breast cancer, or for some women with ductal carcinoma in situ (DCIS). It is not recommended for every case of breast cancer.

Indications

APBI is only considered appropriate for certain cases of early-stage breast cancer and DCIS. Guidelines may change over time, as more research is done.

Early-Stage Breast Cancer

According to 2017 guidelines put out by The American Society for Radiation Oncology, women with early-stage breast cancer are considered candidates for APBI if they:

  • Are age 50 or olderHave clean surgical margins of at least 2 millimeters (mm)

It may be considered as a “cautionary” treatment for women who:

  • Are between 40 and 49 years oldHave clean surgical margins that are close to 2 mm

APBI is not recommended for women under 40.

Ductal Carcinoma in Situ

Women with DCIS are considered candidates only if they meet all criteria for the definition of low-risk DCIS, including:

  • Screening-detected diseaseTumor size of 2.5 centimeters or smallerClean surgical margins of 3 mm or greater

Types of APBI

APBI is actually an umbrella term for different radiation methods. Two of these are internal radiation therapies (brachytherapy), which means they irradiate a tumor from inside the body via implants:

  • Multi-catheter internal radiationBalloon internal radiation

The newest type of accelerated treatment, on the other hand, uses external irradiation. That is, radiation is targeted with a beam from outside the body.

  • 3-D conformal external beam radiation (3DCRT)

Because of this, it can be easy to initially mix 3DCRT up with the long-used standard form of radiation, external beam radiation therapy (EBRT). But unlike 3DCRT, EBRT involves irradiating the whole breast, rather than a targeted area of it (which is why EBRT is referred to as whole-breast irradiation, or WBI).

Multi-Catheter Internal Radiation

Multi-catheter internal radiation—a.k.a. multi-catheter interstitial brachytherapy, or MIB— involves several small tubes (catheters) or sometimes a single device that deploys multiple catheters after it’s inserted into the area where your tumor used to be.

The catheters are stitched into place and the ends stick out through your skin. A machine then puts small bits of radioactive material, called seeds, into the catheters. They’re left in until the desired amount of radiation is delivered, then they are removed.

Low-dose treatments require longer exposure, so the seeds are left in for anywhere from a few hours to a few days. You have to be in the hospital for the duration because of the radioactivity inside you. Once your treatment is over, the catheters and seeds are removed and you’ll be released.

For high-dose treatments, the typical course is twice a day (about an hour each time) for five days. The seeds deliver a quick blast of radiation for 10 minutes or less and are then removed. It’s safe for you to leave the hospital immediately after each treatment. The catheters are removed at the end of the five days.

Several devices are on the market for multi-catheter internal radiation, including one called SAVI.

Balloon Internal Radiation

In balloon internal radiation (also called balloon catheter radiation), the radioactive seeds are delivered into your breast via a catheter attached to a balloon or a device that expands like a balloon once it’s placed inside you.

Balloon catheters are available in two models:

  • Single-source, where one catheter contains the radiation doseMultiple-source, where several catheters contain the radiation doses

A typical course of treatment is twice a day for five to seven days. Sessions generally take about half an hour. As with multi-catheter radiation, a machine inserts the seed (or possibly multiple seeds, depending on the model), the radiation is delivered, and the seed is removed. You can go home in between treatments.

Once your treatment is completed, the balloon(s) and the catheter(s) are removed.

Multiple balloon devices are in use, including MammoSite and ClearPath.

3-D Conformal External Beam Radiation

3DCRT is a form of APBI in which magnetic resonance imaging (MRI) or a computed tomography (CT) scan of the breast maps out small at-risk areas for treatment. These are designed to maximize radiation to those specific areas while minimizing exposure to the healthy surrounding tissues.

A machine called a linear accelerator then delivers the radiation externally. This is the same machine used for whole-breast irradiation.

Treatment with 3DCRT generally is given twice a day for a week. You can leave the facility in between treatments.

Effectiveness

The standard form of whole-breast irradiation is proven to be effective at reducing the risk of recurrence. Partial-breast treatments are newer and the medical community is just beginning to get a look at long-term outcomes.

The results of two long-term follow-up studies comparing outcomes of WBI and APBI were presented at the San Antonio Breast Cancer Symposium in December of 2018.

One study, conducted in the United States, followed more than 4,000 breast cancer survivors who had a lumpectomy followed by either WBI or APBI. Ten years after treatment, outcomes for both groups were considered good, with 95% not having a recurrence.

Of the 161 participants who did have a recurrence of breast cancer:

  • 90 had received APBI71 had received WBI

So while the APBI group had a slightly higher recurrence rate, the difference is extremely small.

Researchers involved in this study said they had not yet analyzed the recurrence risk by type of breast cancer at the time of the presentation. It was a varied group of participants, including:

  • DCIS in 25%Stage 1 breast cancer in 65%Stage 2 breast cancer in 10%Hormone receptor-positive cancer in 81%Postmenopausal cases in 61%

The other study included more than 2,000 participants from Canada, Australia, and New Zealand and compared WBI to APBI with 3DCRT. In this group, 18% had DCIS and 82% had invasive breast cancer.

The five-year recurrence rates were:

  • 2.3% for APBI1.7% for WBI

The eight-year recurrence rates were:

  • 3% for APBI2.8% for WBI

Again, the differences were extremely small, leading researchers to conclude that APBI is an acceptable choice for many women.

Potential Advantages

Several advantages lead women and their healthcare providers to consider APBI, such as:

  • Shorter treatment duration (five to seven days versus five to seven weeks with whole-breast irradiation): This means less disruption of your schedule, less travel time, and fewer co-payments.
  • Fewer side effects: With whole-breast radiation, healthy cells in the radiation area are affected along with the cancer cells, causing issues like skin burns and tissue thickening. APBI is more precise in terms of the area it targets, which minimizes harm to surrounding tissues.
  • Less fatigue: Standard radiation may cause fatigue, but with brachytherapy, you should be able to go about life as usual.

Disadvantages

The disadvantages are due to the catheters used in internal forms. They include:

  • The need to avoid showers during the duration of treatmentThe possibility of infection around the catheter insertion siteFinding a bra that doesn’t interfere with the cathetersPossibly needing to adjust your sleeping position for comfort

Side Effects

You may have some side effects during or after internal APBI treatments. These should clear up with proper care, but make sure to go to your follow-up appointments and let your healthcare provider know if you have concerns about your recovery.

You can expect some redness or bruising around the insertion site. There may also be some pain or drainage from the scar before it heals. Take care to keep this area clean and dry. Some women may develop a skin reaction or rash.

A Word From Verywell

Healthcare providers are learning more about APBI all the time, so information may be changing rapidly. Make sure you know the advantages and disadvantages of the types of radiation available to you and consider the latest research. Work closely with your healthcare provider to weigh the options and make the right decision for protecting your long-term health.

If skin redness persists, or the area becomes puffy or looks inflamed, see your healthcare provider right away to determine if you may have an infection.