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.