To present guidance for patients and physicians regarding the use of accelerated partial-breast irradiation (APBI), based on current published evidence complemented by expert opinion.

A systematic search of the National Library of Medicine's PubMed database yielded 645 candidate original research articles potentially applicable to APBI. Of these, 4 randomized trials and 38 prospective single-arm studies were identified. A Task Force composed of all authors synthesized the published evidence and, through a series of meetings, reached consensus regarding the recommendations contained herein.

The Task Force proposed three patient groups: (1) a "suitable" group, for whom APBI outside of a clinical trial is acceptable, (2) a "cautionary" group, for whom caution and concern should be applied when considering APBI outside of a clinical trial, and (3) an "unsuitable" group, for whom APBI outside of a clinical trial is not generally considered warranted. Patients who choose treatment with APBI should be informed that whole-breast irradiation (WBI) is an established treatment with a much longer track record that has documented long-term effectiveness and safety.

Accelerated partial-breast irradiation is a new technology that may ultimately demonstrate long-term effectiveness and safety comparable to that of WBI for selected patients with early breast cancer. This consensus statement is intended to provide guidance regarding the use of APBI outside of a clinical trial and to serve as a framework to promote additional clinical investigations into the optimal role of APBI in the treatment of breast cancer.