Are the American Society for Radiation Oncology guidelines accurate predictors of recurrence in early stage breast cancer patients treated with balloon-based brachytherapy?

The American Society for Radiation Oncology (ASTRO) consensus statement (CS) provides guidelines for patient selection for accelerated partial breast irradiation (APBI) following breast conserving surgery. The purpose of this study was to evaluate recurrence rates based on ASTRO CS groupings. A single institution review of 238 early stage breast cancer patients treated with balloon-based APBI via balloon based brachytherapy demonstrated a 4-year actuarial ipsilateral breast tumor recurrence (IBTR) rate of 5.1%. There were no significant differences in the 4-year actuarial IBTR rates between the "suitable," "cautionary," and "unsuitable" ASTRO categories (0%, 7.2%, and 4.3%, resp., P = 0.28). ER negative tumors had higher rates of IBTR than ER positive tumors. The ASTRO groupings are poor predictors of patient outcomes. Further studies evaluating individual clinicopathologic features are needed to determine the safety of APBI in higher risk patients.