Background: The American Society for Radiation Oncology (ASTRO) consensus statement (CS) for the application of accelerated partial breast irradiation (APBI) was applied to patients who were treated with this technique on the American Society of Breast Surgeons MammoSite Registry Trial to determine potential differences in clinical outcome based on classification group.
Methods: Patients were classified based on the CS groups of "suitable," "cautionary," and "unsuitable." Rates of ipsilateral breast tumor recurrence (IBTR), regional lymph node failure, distant metastases, disease-free survival, cause-specific survival, and overall survival were assessed.
Results: Of the 1449 cases who were treated, 1025 patients (71%) could be classified according to the CS groupings, including 419 patients (41%) who fit the "suitable" criteria, 430 patients (42%) who fit the "cautionary" criteria, and 176 patients (17%) who fit the "unsuitable" criteria. At a median follow-up of 53.5 months, the 5-year actuarial rates of IBTR for the "suitable," "cautionary," and "unsuitable" groups were 2.59%, 5.43%, and 5.28%, respectively (P = .1884). Univariate analysis of factors potentially associated with IBTR indicated that negative estrogen receptor status was the only variable associated with IBTR among patients with invasive breast cancer (odds ratio [OR], 4.01; P = .0003). Larger tumor size was associated with a greater risk of distant metastasis (OR, 3.05; P = .0001). Among patients with ductal carcinoma in situ, only age <50 years and close-positive margins were associated with IBTR (OR, 1.12 [P = .0079] and OR, 7.81 [P = .0131], respectively).
Conclusions: The ASTRO CS groupings did not differentiate a subset of patients with a significantly worse rate of IBTR when they were treated with the MammoSite breast brachytherapy catheter to deliver APBI.
© 2010 American Cancer Society.