Outcomes of selective whole breast irradiation following lumpectomy with intraoperative radiation therapy for hormone receptor positive breast cancer.

Background: For low risk breast cancer, the TARGIT-A randomized trial supported lumpectomy with intraoperative radiation therapy (IORT) and selective whole breast radiation (WBXRT). Selection criteria for WBXRT vary.

Methods: Women with hormone-receptor positive, clinically node-negative breast cancer were categorized retrospectively as suitable for IORT alone or also needing WBXRT by TARGIT-A or expanded TARGIT criteria (TARGIT-MCC). We evaluated local recurrence (LR) by selection criteria and receipt of WBXRT.

Results: Among 194 cases followed a median of 44 months, 54 (27.8%) met TARGIT-MCC criteria for WBXRT (34 met TARGIT-A criteria). Thirty patients were recommended and 21 (10.8%) received WBXRT. Of 13 patients with LR, none received WBXRT. LR was 10.5% in patients meeting TARGIT-MCC criteria who did not receive WBXRT versus 0% after WBXRT (p = 0.299).

Conclusions: Selective WBXRT may have mitigated LR. Nearly all LR were in patients not recommended WBXRT. Further work should refine criteria for WBXRT after IORT.

Summary: Prior work among women with early breast cancer supported lumpectomy with intraoperative radiation therapy and selective adjuvant radiation using a risk-adapted approach. An expanded set of criteria for adjuvant radiation appear to further mitigate local recurrence risk. Local recurrence after lumpectomy with IORT could be further minimized by identification of additional high-risk features, as well as greater adherence to adjuvant endocrine therapy.