Risk-Stratified Intraoperative Radiation Therapy as a Definitive Adjuvant Radiation Therapy Modality for Women With Early Breast Cancer.

Radiation therapy is an integral component of adjuvant therapy in women who undergo breast conservative surgery, decreasing the likelihood of tumor recurrence and extending survival. The likelihood of tumor recurrence is highest within a proximity of the lumpectomy cavity, which prompted the idea of partial breast irradiation in place of the usual standard-of-care treatment with external beam whole breast radiation therapy. Targeted intraoperative radiation therapy (TARGIT-A) is a multicenter trial initially developed in 1999 and designed as a randomized clinical trial comparing whole breast radiation therapy to risk-adapted intraoperative radiation therapy (IORT). TARGIT-A recruited its first patient in March 2000, with the study concluding in 2012. At a median follow-up of 8.6 years, the prepathology TARGIT-A trial noted results to be noninferior to external beam radiation therapy, with no statistically significant difference in ipsilateral breast tumor recurrence, mastectomy-free survival, distant disease-free survival, or breast cancer-specific mortality. These results are consistent with the majority of retrospective and prospective trials. Risk-adapted IORT, as performed in the prospective randomized TARGIT-A trial, gives level 1 evidence that this approach is a standard option in the treatment of breast cancer.