Factors associated with optimal cosmetic results at 36 months in patients treated with accelerated partial breast irradiation (APBI) on the American Society of Breast Surgeons (ASBrS) MammoSite Breast Brachytherapy Registry Trial.

PURPOSE: To evaluate factors associated with optimal cosmetic results at 36 months for early-stage breast cancer patients enrolled on the American Society of Breast Surgeons (ASBrS) MammoSite Breast Brachytherapy registry trial.

MATERIALS AND METHODS: 1,440 patients (1,449 cases) with early-stage breast cancer undergoing breast-conserving therapy were treated with the MammoSite radiation therapy system (RTS) brachytherapy catheter to deliver adjuvant accelerated partial breast irradiation (APBI) (34 Gy in 3.4-Gy fractions). Cosmetic outcome was evaluated at each follow-up visit and dichotomized as excellent/good or fair/poor. Median follow-up for surviving patients was 43.0 months (range 0-73.0 months).

RESULTS: The percentage of patients with good/excellent cosmetic results at 12, 24, 36, and 48 months were as follows: 94.5% (n = 950/1,005), 93.8% (n = 781/833), 93.1% (n = 683/734), and 90.4% (n = 520/575), respectively. Three-year absolute rates of good/excellent cosmesis were as follows: breast-related wound infection (BWI) (83.3%) versus no BWI (94%), <7 mm skin spacing (87.5%) versus >or=7 mm skin spacing (93.6%). Using multiple regression analysis, factors predictive of worse cosmetic outcome at 36 months included smaller skin spacing [odds ratio (OR) 1.06, confidence interval (CI) 1.01-1.12] and BWI (OR 0.33, CI 0.16-0.70). A predictive model developed showed that presence of a BWI, use of chemotherapy, and skin spacing had the most effect on cosmetic outcomes. However, in patients that did not develop a breast infection, skin spacing and use of chemotherapy had the most effect on cosmesis.

CONCLUSION: APBI delivered by MammoSite brachytherapy lead to good/excellent cosmesis in 93% of patients with 3-year follow-up. Breast wound infection, use of chemotherapy, and skin spacing were found to be the three most important predictors of cosmesis at 36 months in our cohort of patients.