Study finds side effects, complications, mastectomy more likely after partial breast irradiation

Accelerated partial breast irradiation (APBI) brachytherapy, the localized form of radiation therapy growing increasingly popular as a treatment choice for women with early-stage breast cancer, is associated with higher rate of later mastectomy, increased radiation-related toxicities and post-operative complications, compared to traditional whole breast irradiation (WBI), according to researchers from The University of Texas MD Anderson Cancer Center.

The retrospective study was presented in the CTRC-AACR San Antonio Breast Cancer Symposium's press briefing by Benjamin Smith, M.D., assistant professor in the Department of Radiation Oncology, and in the meeting's scientific session by Grace Smith, M.D., Ph.D., a resident in MD Anderson's Department of Radiation Oncology and the study's first author.

"Our study compared the two radiation therapy techniques available to women with early-stage breast cancer. We found that women treated with accelerated partial breast irradiation therapy have a two-fold increased risk for subsequent mastectomy, most likely because of tumor recurrence or local complications, as well as an increased risk for post-operative and radiation-related complications," said Ben Smith, the study's senior author.

There are numerous types of APBI; the MD Anderson study only looked at the brachytherapy technique, in which a form of radiation treatment involving insertion of a catheter containing a radioactive source to kill breast cancer cells that may remain after lumpectomy surgery. A specialized catheter is surgically inserted into the cavity left behind after tumor removal. APBI brachytherapy is performed a few weeks after a lumpectomy, twice daily over a course of five to seven days.

APBI brachytherapy has grown in popularity over the past decade, since earlier studies showed generally low cancer recurrence rates, though most prior studies have not directly compared the outcomes of APBI brachytherapy to traditional radiation therapy, explained Ben Smith.

The first commercially-available single catheter to deliver partial breast irradiation was approved by the FDA in 2002, escalating APBI's use, said Ben Smith.

The MD Anderson study was based on analysis of claim forms filed by 130,535 Medicare beneficiaries nationwide, who were diagnosed with cancer between 2000 and 2007.

"In our study of Medicare patients, we found a consistent increase in APBI brachytherapy, from less than 1 percent in 2000 to 13 percent in 2007. It's our guess that this trend has continued," said Smith.

There are benefits to the practicality APBI offers women, noted Ben Smith.

"For whole breast irradiation, the standard treatment time is between five and seven weeks, but studies have shown that some women experience delays or have obstacles completing their course of radiation. Treatment delays and incompletion are known to increase the risk of cancer recurrence in the breast. APBI brachytherapy is attractive because it has the potential to address those issues, because treatment only lasts one week."