Comparison of survival and regional failure between accelerated partial breast irradiation and whole breast...

To compare rates of regional recurrence (RR) and overall survival (OS) between a pooled set of 1400 patients treated on the American Society of Breast Surgeons MammoSite (Hologic, Inc., Bedford, MA) Registry Trial to a cohort of 3600 patients treated with whole breast irradiation (WBI).

A total of 1440 women underwent accelerated partial breast irradiation (APBI) between 2002 and 2004 as part of the American Society of Breast Surgeons Registry Trial and a total of 3593 patients who received WBI were evaluated from the Surveillance Epidemiology and End Results database with treatment received between 1980 and 2009. A matched-pair analysis was performed based on age, receipt of hormonal therapy, chemotherapy, nodal status, and tumor size (1051 patients per arm). Rates of RR and OS were then analyzed for each group.

After the match, no differences in patient characteristics were noted when tumor size was evaluated as a continuous variable. Rates of RR and OS were similar between the WBI and APBI groups. A Cox regression model found no difference between WBI and APBI with regard to RR; however, OS was improved in the APBI cohort (hazard ratio 0.008, p<0.0001).

With one of the largest patient populations to date comparing WBI and APBI, no difference in RR or OS was noted between WBI and APBI treatment. Until the publication of prospective Phase III trials, these data support the continued use of APBI on protocol and off protocol in appropriately selected patients.