Results showed that the 10-year actuarial risk of an ipsilateral breast tumor recurrence was 7.6%, which were “in line” with the 10% reported in the Early Breast Cancer Trialists’ Group meta-analysis after lumpectomy and WBI. Regional failure was 2.3%, distant metastasis was 3.8%; cause-specific survival was 96.3%, overall survival was 86.5%, and new contralateral cancers was 4.6%.
The only two significant variables associated with an increased risk of local recurrence on multivariate analysis were high grade (hazard ratio=2.81) and positive margin status (hazard ratio=18.42). In 116 patients with 5 or more years of follow-up, physician-reported cosmesis was excellent or good in 84% of patients.
In the United States, high-dose rate brachytherapy (HDR) is preferred to low-dose rate because “a temporary source enters the applicator for treatment and then the source goes back into a vault and so the patient is just left with an applicator with no source in it,” Dr. Kamrava said.
“It allows the woman to be treated as an outpatient without exposing anyone else to radiation.” Standard HDR is 3.4 Gy x 10 treatments and in Europe “many will also do 4 Gy x 8 treatments.”
He added that “multicatheter tube and button is the most versatile technique and can be used regardless of the shape, size, or location of the seroma cavity.” He said it is difficult to know exactly what percentage of women with breast cancer are being treated with adjuvant APBI. A publication from 2012 suggests it is about 15% of those older than 66.2
In the study, “cautionary” and “unsuitable” women under ASTRO guidelines were treated with APBI. When asked whether this suggests that the ASTRO guidelines are not that closely adhered to, or rather, represents a change in treatment over the past 2 decades, Dr. Kamrava told Cancer Therapy Advisor that “women on this study were treated well before there were any guidelines. When the guidelines came out, they were based on the data that were available at that time, but also on expert opinion. In many cases, there weren’t data available to guide decision-making. Placing a patient in a ‘cautionary’ group didn’t mean that there were necessarily any data to suggest that their outcomes were actually worse with partial breast, but that the panel thought people should be cautious with those features.”
RELATED: Modest Association Between C-reactive Protein, Breast Cancer Risk
Dr. Kamrava explained that as more data have been collected since the publication of the guidelines, multiple studies show that the guidelines are likely too conservative and do not seem to predict for groups of women that have a higher risk of recurrence after partial breast radiation.
The group is currently using the registry data to examine outcomes by breast cancer subtypes (eg, luminal A, luminal B), outcomes by ASTRO consensus guidelines groupings (ie, suitable, cautionary, unsuitable), and factors influencing long-term cosmetic outcomes.
- Kamrava M, Kuske RR, Anderson B, et al. Outcomes of breast cancer patients treated with accelerated partial breast irradiation via multicatheter interstitial brachytherapy: the Pooled Registry of Multicatheter Interstitial Sites (PROMIS) experience. [published online ahead of print April 28, 2015]. Ann Surg Oncol. doi: 10.1245/s10434-015-4563-7.
- Presley CJ, Soulos PR, Herrin J, et al. Patterns of use and short-term complications of breast brachytherapy in the national Medicare population from 2008-2009. J Clin Oncol. 2012;30(35):4302-4307.