Four-year clinical update from the American Society of Breast Surgeons MammoSite brachytherapy trial.

BACKGROUND: We present a 4-year update on the efficacy, cosmetic results, and complications of MammoSite breast brachytherapy in patients enrolled in the American Society of Breast Surgeons registry trial. METHODS: A total of 1,449 breasts in 1,440 patients with early stage breast cancer undergoing breast-conserving therapy were treated with adjuvant, accelerated partial breast irradiation (APBI) (34 Gy in 3.4-Gy fractions) delivered with the MammoSite device. The median follow-up period for the entire group was 36.1 months. RESULTS: The 3-year actuarial rate of ipsilateral breast tumor recurrence was 2.15%. The 3-year actuarial rate of axillary recurrence was .36%. Complication rates were as follows: infection, 9.5%; seroma, 26.8% (symptomatic seroma, 12.7%); and fat necrosis, 2.0%. The percentages of breasts with good or excellent cosmetic results were as follows: 12 months, 95%; 24 months, 94%; 36 months, 94%; and 48 months, 91%. CONCLUSIONS: Locoregional control, complications, and cosmetic outcomes from MammoSite APBI at the 4-year update are acceptable and similar to results seen with other forms of APBI