What Is a Radiation Boost for Breast Cancer?

A radiation boost for breast cancer sounds like what it is—an extra radiation dose given after the regular sessions of radiation are complete. While the bulk of radiation therapy focuses on the whole breast, a boost targets the area where the primary tumor was located. The goal is to reduce the likelihood of breast cancer recurrence.

When and How It's Done

Breast cancer is often treated with surgery, either a lumpectomy or mastectomy. In addition to surgery, other treatments may be given, such as chemotherapy and radiation therapy, which is treatment with high-energy rays or particles that kill cancer cells. The most common type of radiation therapy given after a lumpectomy (breast-conserving surgery), is external beam radiation of the whole breast. Radiation to the chest wall may also be given after a mastectomy, particularly if lymph nodes are positive.

If you receive radiation treatment and a radiation boost is planned, it will be administered after your whole breast irradiation treatment sessions are complete.

More specifically, a radiation boost includes one or more extra treatments targeted at the tumor bed, which is a small area of breast tissue where the original cancer was removed. Surgeons usually mark this area with surgical clips (made out of titanium) that remain in the body so that the boost can be delivered to this critical area.

Effect on Recurrence and Survival

A radiation boost may be given either after a lumpectomy or a mastectomy, though the focus of the boost is different.

Radiation Boost After Lumpectomy

Research has shown that women who undergo a radiation boost have fewer local breast cancer recurrences than women who do not undergo a boost, with a reduction in recurrence most likely among women 50 or younger who are diagnosed with ductal carcinoma in situ (DCIS).

That said, even though a radiation boost significantly reduces the risk of breast cancer recurrence, it does not appear to have any effect on overall survival up to 20 years out after treatment. 

Radiation Boost After Mastectomy

The same has been noted when a radiation boost has been used for women who had a mastectomy. While a radiation boost reduces local chest wall recurrence of breast cancer, this hasn't been found to translate into longer survival.

From a different angle, however, a radiation boost after mastectomy does appear to influence the success of reconstruction, with those who have a boost being more likely to have unsuccessful surgery. What this means is that each woman will need to weigh the lower risk of a chest wall recurrence against the higher risk that reconstruction won't be successful when making a decision.

Side Effects

A radiation boost is generally tolerated quite well, carrying the same side effects as whole breast radiation, including fatigue, swelling of the breast, and skin changes like redness, blistering, peeling, and darkening of the skin. 

In terms of long-term effects, radiation fibrosis of the breast may occur. This is the formation of scar tissue in the area that was radiated, potentially altering the appearance of the breast.

A 2015 study found that women who had a radiation boost were at an increased risk of developing moderate to severe breast fibrosis. In general, though, research supporting this finding is not robust.

There is some concern with left sided breast cancer that radiation could have negative long-term effects on the heart. A newer technique of breath-holding is used by some cancer centers to reduce this risk. If you will be having radiation therapy, you may wish to talk to your radiation oncologist about this option.

A Word From Verywell

While receiving an extra dose of radiation may seem scary or unnecessary, you can take comfort knowing that the goal of this boost is to minimize the chances of your breast cancer returning. If your doctor suggests one, but you are uncertain about moving ahead with it, have an open discussion about your concerns and ask the specific reasons behind the recommendation in your case.