Mastectomy risk reduced by external beam radiation for invasive breast cancer

Standard external beam radiation therapy (EBRT) provided a higher breast preservation rate than brachytherapy in women 66 years and older with invasive breast cancer, according to new research.

Brachytherapy after lumpectomy is an increasingly popular treatment protocol for breast cancer; however, there is conflicting data regarding its effectiveness. In addition, published suitability criteria directing patient selection for brachytherapy have not been empirically validated. This study compared the long-term likelihood of breast preservation, risks of postoperative complications and local toxicities, and validity of suitability categories of three treatment strategies after lumpectomy: EBRT, brachytherapy, and no radiation. 

This study, published in the International Journal of Radiation Oncology ● Biology ● Physics (2014;88[2]:274-284), used the Surveillance, Epidemiology and End Results (SEER)–Medicare-linked database to identify 35,947 women, age 66 years and older, with invasive breast cancer (79.9%) or ductal carcinoma in situ (DCIS; 20.1%) between 2002 and 2007, and treated with lumpectomy alone (23%), lumpectomy followed by brachytherapy (3.6%), or lumpectomy followed by EBRT (73.4%). Patients with invasive breast cancer were also classified as suitable (34.7%), cautionary (17.6%), or unsuitable (35.2%) for brachytherapy based on the American Society for Radiation Oncology's (ASTRO's) Accelerated Partial Breast Irradiation Consensus Statement. The patients with DCIS in this study were analyzed separately. For this study, patients age 70 years and older were classified as older suitable. 

The median follow-up for patients was 3.5 years. The 5-year cumulative incidence of subsequent mastectomy for patients with invasive breast cancer was 4.7% for those treated with lumpectomy alone, 2.8% for those treated with lumpectomy followed by brachytherapy, and 1.3% for those treated with lumpectomy followed by EBRT. In patients with DCIS, 2.2% underwent subsequent mastectomy during follow-up. The 5-year cumulative incidence of subsequent mastectomy in patients with DCIS was 3.2% for those treated with lumpectomy alone, 4.6% for those treated with brachytherapy, and 1.6% for those treated with EBRT. 

In this study, brachytherapy was associated with a greater likelihood of breast preservation than lumpectomy alone, while EBRT showed more likelihood of breast preservation than brachytherapy. When stratified into the ASTRO-defined suitability groups, the study found that patients in the suitable group were the least likely to undergo subsequent mastectomy and had the smallest absolute difference when comparing those treated with brachytherapy and those treated with EBRT. The small number of patients with DCIS treated with brachytherapy in this cohort does not allow definitive conclusions on the effectiveness of brachytherapy for these patients. 

“Brachytherapy offered a breast preservation benefit, although in general this benefit was slightly less than the benefit derived from standard external beam radiation therapy,” said coauthor Benjamin D. Smith, MD, of The University of Texas MD Anderson Cancer Center in Houston. “Our findings suggest that certain patients with very favorable tumors do just as well with either brachytherapy or standard external beam radiation therapy, whereas other patients with higher-risk tumors seem to do better with standard external beam radiation th
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