Limitations of the American Society of Therapeutic Radiology and Oncology Consensus Panel guidelines on the use of accelerated partial breast irradiation.

PURPOSE We applied the American Society of Therapeutic Radiology and Oncology (ASTRO) Consensus Panel (CP) guidelines for the use of accelerated partial breast irradiation (APBI) to patients treated with this technique to determine the ability of the guidelines to differentiate patients with significantly different clinical outcomes. METHODS AND MATERIALS A total of 199 patients treated with APBI and 199 with whole-breast irradiation (WBI) (matched for tumor size, nodal status, age, margins, receptor status, and tamoxifen use) were stratified into the three ASTRO CP levels of suitability ("suitable," "cautionary," and "unsuitable") to assess rates of ipsilateral breast tumor recurrence (IBTR), regional nodal failure, distant metastases, disease-free survival, cause-specific survival, and overall survival based on CP category. Median follow-up was 11.1 years. RESULTS Analysis of the APBI and WBI patient groups, either separately or together (n = 398), did not demonstrate statistically significant differences in 10-year actuarial rates of IBTR when stratified by the three ASTRO groups. Regional nodal failure and distant metastasis were generally progressively worse when comparing the suitable to cautionary to unsuitable CP groups. However, when analyzing multiple clinical, pathologic, or treatment-related variables, only patient age was associated with IBTR using WBI (p = 0.002). CONCLUSIONS The ASTRO CP suitable group predicted for a low risk of IBTR; however, the cautionary and unsuitable groups had an equally low risk of IBTR, supporting the need for continued refinement of patient selection criteria as additional outcome data become available and for the continued accrual of patients to Phase III trials.