Differences in patterns of failure in patients treated with accelerated partial breast irradiation versus whole-breast irradiation: a matched-pair analysis with 10-year follow-up.

PURPOSE: To examine 10-year results of a single institution's experience with radiotherapy limited to the region of the tumor bed (i.e., accelerated partial breast irradiation, [APBI]) in selected patients treated with breast-conserving therapy (BCT) and compare them with results of matched BCT patients who underwent whole-breast irradiation (WBI).

PATIENTS AND METHODS: A total of 199 patients with early-stage breast cancer were treated prospectively with BCT and APBI using interstitial brachytherapy. To compare potential differences in local recurrence rates on the basis of the volume of breast tissue irradiated, patients in the APBI group were matched with 199 patients treated with WBI. Match criteria included tumor size, nodal status, age at diagnosis, margins of excision, estrogen receptor status, and use of adjuvant tamoxifen therapy. Local-regional control, disease-free survival, and overall survival were analyzed between treatment groups.

RESULTS: Median follow-up for surviving patients was 9.6 years (range, 0.3-13.6 years). Eight ipsilateral breast tumor recurrences (IBTRs) were observed in patients treated with APBI. The cumulative incidence of IBTR at 10 years was 5%. On matched-pair analysis, the rate of IBTR was not statistically significantly different between the patient groups (4%, 95% confidence interval [CI] 1.3-6.7% for WBI therapy patients vs. 5%, 95% CI 1.5-8.5% for APBI patients; p = 0.48).

CONCLUSIONS: Radiation therapy limited to the region of the tumor bed (APBI) produced 10-year local control rates comparable to those from WBI in selected low-risk patients.