When comparing treatments designed to enable long-term breast preservation for older women with invasive breast cancer, researchers found that those treated with brachytherapy were at higher risk for a later mastectomy, compared with women treated with standard radiation therapy.

The findings, published in the International Journal of Radiation Oncology*Biology*Physics (2014; doi:10.1016/j.ijrobp.2013.07.011), are the first to provide a direct comparison of breast brachytherapy against a lumpectomy-alone control group and an external-beam radiation therapy (EBRT) control group. They also conducted additional analysis of the American Society for Radiation Oncology’s (ASTRO’s) criteria for selecting treatment options.

Brachytherapy delivers radiation to a specific region within the breast through the insertion of a catheter, which decreases treatment periods to 1 or 2 weeks compared with EBRT’s 4- to 6-week regimen. The authors noted that brachytherapy is an increasingly popular breast cancer treatment used following lumpectomy.

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However, questions remain whether this treatment should be the standard of care based on the uncertainty of which patients may benefit and which patients might incur potential harms.

“We were interested in comparing how well different treatment strategies work to enable long-term breast preservation,” said lead author Benjamin Smith, MD, of The University of Texas MD Anderson Cancer Center in Houston. “Our results could impact care by helping patients and providers understand the tradeoffs between these two treatment strategies in greater detail.”

To conduct the study, researchers used the Surveillance, Epidemiology and End Results Medicare database (SEER), compiled by the National Cancer Institute, to identify 35,947 women age 66 years and older who were treated with lumpectomy for breast cancer between 2002 and 2007.

The 5-year subsequent mastectomy risk was 4.7% after lumpectomy alone, 2.8% after brachytherapy, and 1.3% after EBRT. Researchers concluded that, within each ASTRO group, EBRT consistently showed the lowest subsequent mastectomy risk versus lumpectomy alone, whereas brachytherapy consistently showed some benefit versus lumpectomy alone, but not as much as EBRT.

However, the authors found that, among patients who were deemed suitable for brachytherapy by the ASTRO consensus statement on partial breast radiation, long-term breast preservation rates were similar for EBRT and brachytherapy. Specifically, in this group, the incidence of subsequent mastectomy was 1.6% for brachytherapy versus 0.8% for EBRT.

Smith said that the data provide some support of the ASTRO guidelines, while indicating that, for patients who do not meet stringent criteria of ASTRO, offering brachytherapy must be done more carefully. He concluded, “The takeaway message to both physicians and older breast cancer patients is that, in general, all of these patients did well with very high likelihood of breast preservation. However, likelihood of breast preservation was best with external beam radiation, worst with no radiation, and in between with brachytherapy.”