Is partial breast irradiation a step forward or backward?

Partial-breast irradiation (PBI) may prove to be a significant advance in the treatment of selected patients with early-stage breast cancer. However, because PBI treats a much smaller volume of breast tissue than does conventional whole-breast irradiation and the biologic equivalent dose delivered to the tumor may be considerably lower, it is possible that this treatment approach may increase the risk of recurrence. There may also be an increased risk of toxicity using PBI techniques that have significant dose inhomogeneity. Despite these uncertainties, many patients in the United States are currently treated with PBI outside of a clinical study. Showing that PBI is safe and effective requires having results from large clinical trials. If such trials are supported and completed, the benefits and limitations of PBI are likely to be elucidated, and this treatment technique, properly refined, may well prove to be an advance in breast cancer care. If instead PBI is adopted ad hoc within the radiation oncology community without proper testing, it is likely that poor outcomes will be underreported and many patients will receive suboptimal therapy. This would be a big step backward in the role of radiation therapy in breast cancer treatment.