Ductal carcinoma in situ treated with breast-conserving surgery and accelerated partial breast irradiation: comparison of the Mammosite registry trial with intergroup study E5194.

Background: The purpose of this study was to determine the ipsilateral breast tumor recurrence (IBTR) in ductal carcinoma in situ (DCIS) patients treated in the American Society of Breast Surgeons MammoSite Breast Brachytherapy Registry Trial who met the criteria for E5194 treated with local excision and adjuvant accelerated partial breast irradiation (APBI).

Methods: A total of 194 patients with DCIS were treated between 2002 and 2004 in the Mammosite registry trial; of these, 70 patients met the enrollment criteria for E5194: 1) low to intermediate grade (LIG)-pathological size >0.3 but <2.5 cm and margins ≥3 mm (n = 41) or 2) high grade (HG)-pathological size <1 cm and margins ≥3 mm (n = 29). All patients were treated with lumpectomy followed by adjuvant APBI using MammoSite. Median follow-up was 52.7 months (range, 0-88.4). SAS (version 8.2) was used for statistical analysis.

Results: In the LIG cohort, the 5-year IBTR was 0%, compared with 6.1% at 5 years in E5194. In the HG cohort, the 5-year IBTR was 5.3%, compared with 15.3% at 5 years in E5194. The overall 5-year IBTR was 2%, and there were no cases of elsewhere or regional failures in the entire cohort. The 5-year contralateral breast event rate was 0% and 5.6% in LIG and HG patients, respectively (compared with 3.5% and 4.2%, respectively, in E5194).

Conclusions: This study found that patients who met the criteria of E5194 treated with APBI had extremely low rates of recurrence (0% vs 6.1% in the LIG cohort and 5.3% vs 15.3% in the HG cohort).