Accelerated Partial Breast Irradiation

Investigational procedure may make radiation therapy accessible to more women.

After undergoing a lumpectomy to remove the part of the breast affected by breast cancer, most women must undergo radiation therapy treatments to eliminate microscopic cancer cells that might remain undetected by clinical examination or breast imaging. The standard course delivers radiation to the entire breast, and consists of six to seven weeks of therapy, five days a week. For women who live far from their radiation facilities, the burden associated with daily trips for almost two months can be too much to bear. As a result, some women have curtailed therapy, or even foregone radiation therapy altogether, despite the increased risk of their cancers recurring.

A new kind of radiation therapy may now alleviate this travel burden and allow more women to complete this highly important therapy, according to Sandra Russo, MD, PhD, MPH, Attending Radiation Oncologist. Accelerated partial breast irradiation, or APBI, is a new form of radiation therapy under investigation for preventing recurrences in women who have undergone surgery for breast cancer. "APBI may be able to shorten the course of radiation from six or seven weeks to just one week," Dr. Russo explains.

APBI is delivered directly to the cavity from which the breast cancer was removed rather than to the entire breast, and at a much higher daily dose compared to that used during the standard whole breast radiation therapy. Because the cumulative amount of radiation given during one week of high dose APBI is approximately equal to that delivered during six to seven weeks of daily low dose irradiation therapy, it is believed that the two methods may be equally effective overall at decreasing the risk of recurrence at the lumpectomy cavity.

There are several methods by which radiation oncologists may deliver APBI to the lumpectomy site. These include an intracavity balloon brachytherapy (MammoSite®),multicatheter interstitial brachytherapy, intraoperative radiation therapy (IORT), and three-dimensional conformal external beam radiation (3DCRT), which involves targeting external beam radiation therapy towards the lumpectomy cavity. All four methods may be used to deliver APBI and are under investigation to determine the optimal dose of radiation needed to achieve the lowest risk of recurrence with the least toxicity. Currently, the radiation oncologists at Columbia University are using 3D-CRT as part of a national clinical trial that is comparing lumpectomy followed by whole breast irradiation to APBI.

Acute effects after external beam radiation include local redness, swelling and tenderness, and occasionally, fatigue, while chronic side effects may include skin changes in the treated area, scar tissue formation in the treated area, and the risk of a local recurrence. According to Dr. Russo,most women undergoing either whole-breast radiation therapy or APBI continue their normal activities during their treatments since the acute side effects are well tolerated. "Although the chronic side effects of whole breast irradiation are well known, it will take years to assess the long term side effects of each APBI technique and the risk of 'elsewhere' recurrences."

"It is hoped that by alleviating the time burden associated with breast irradiation, more women will complete the recommended course of radiation after lumpectomy," Dr. Russo continues. "This could make it possible for more women to undergo breast preservation surgery (lumpectomy) instead of mastectomy, especially in areas where radiation facilities are not available."

Although standard irradiation and APBI should both reduce the risk of local recurrence at the lumpectomy cavity, one concern with APBI is the risk of 'elsewhere' breast recurrence (i.e., in locations other than the lumpectomy cavity). A Phase III multicenter randomized clinical trial comparing whole breast irradiation to APBI is currently underway to evaluate the risk of local recurrence, acute and chronic toxicities, and quality of life associated with APBI compared to whole breast irradiation.

It should be noted that APBI is not offered to women with BRCA gene mutations, because of their increased risk of developing breast cancer.

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