Ductal carcinoma in situ treated with breast-conserving surgery and radiotherapy: a comparison with ECOG study 5194.

Background: Recent data from Eastern Cooperative Oncology Group (ECOG) Study 5194 (E5194) prospectively defined a low-risk subset of ductal carcinoma in situ (DCIS) patients where radiation therapy was omitted after lumpectomy alone. The purpose of the study was to determine the ipsilateral breast tumor recurrence (IBTR) in DCIS patients who met the criteria of E5194 treated with lumpectomy and adjuvant whole breast radiation therapy (RT).

Methods: A total of 263 patients with DCIS were treated between 1980 and 2009 who met the enrollment criteria for E5194: 1) low to intermediate grade (LIG) with size >0.3 cm but <2.5 cm and margins >3 mm (n = 196), or 2) high grade (HG), size <1 cm and margins >3 mm (n = 67). All patients were treated with lumpectomy and whole breast RT with a boost to a median total tumor bed dose of 6400 cGy. Standard statistical analyses were performed with SAS (v. 9.2).

Results: The average follow-up time was 6.9 years. The 5-year and 7-year IBTR for the LIG cohort in this study was 1.5% and 4.4% compared with 6.1% and 10.5% in E5194, respectively. The 5-year and 7-year IBTR for the HG cohort was 2.0% and 2.0% in this study compared with 15.3% and 18% in E5194, respectively.

Conclusions: Adjuvant whole breast radiation therapy reduced the rate of local recurrence by more than 70% in patients with DCIS who met the criteria of E5194 (6.1% to 1.5% in the LIG cohort and 15.3% to 2% in the HG cohort). Additional follow-up is necessary given that 70% of IBTRs occurred after 5 years.