2920 - Evaluating the Safety and Short-Term Outcomes of Adjuvant Partial Breast Irradiation Following Breast-Conserving Surgery with Adjacent Tissue Transfer
Presenter(s)
D. Brown1, K. Walker2, S. Gehr2, D. R. Penberthy2, D. R. Brenin3, L. T. Dengel3, A. T. Schroen3, S. Showalter3, S. R. Khandelwal2, and E. M. Janowski2; 1School of Medicine, University of Virginia, Charlottesville, VA, 2Department of Radiation Oncology, University of Virginia, Charlottesville, VA, 3Department of Surgery, University of Virginia, Charlottesville, VA
Purpose/Objective(s): Oncoplastic breast surgery (OBS) following breast-conserving surgery (BCS) improves patient-reported aesthetic outcomes, and techniques can vary from adjacent tissue transfer (ATT) to breast reduction and volume replacement. While partial breast radiation (PBI) is typically contraindicated in patients receiving OBS, there is no data evaluating safety in patients receiving OBS with ATT.
Materials/Methods: In this single-institution retrospective study, all patients underwent hypofractionated external beam PBI (30 Gy in 5 fractions) following BCS. Whole-breast volumes were collected on computer tomography (CT) scans. BCS cavity and planning tumor volumes were generated using CT visualization of surgical clips placed intraoperatively with routine PBI expansions. Adverse events were prospectively recorded and graded using the CTCAE v4.0. Adherence to endocrine therapy was self-reported during follow-up.
Results: A total of 122 patients were analyzed: 96 with ATT and 26 controls without ATT. Cohorts did not differ significantly in median age (68 vs. 70, p = 0.42), tumor sizes (8.0 mm vs. 6.5 mm, p = 0.84), or histology (ER-positivity: 97% vs 96%, PR-positivity: 63% vs. 73%, p = 0.32, and HER2-overexpression: 1% vs. 0%). Distributions of Tis/T1/T2 disease were similar between groups (p = 0.87), and ATT was not associated with an increased incidence of final surgical margins <2 mm (17% vs. 19%). 50% of the control group and 67% of the ATT group were considered suitable for PBI (p = 0.12). Median planning tumor volumes (118 cc vs. 121 cc) were similar, although the control group had greater median ipsilateral breast volumes (734 cc vs. 1126 cc, p < 0.001). The frequencies of overall adverse events (74% vs. 77%) and grade = 2 events (16% vs. 15%) were similar at four months of follow-up. Control patients experienced higher rates of breast pain (14% vs. 35%, p = 0.04). While the two groups had no difference in adjuvant endocrine therapy initiation (61% vs. 62%), patients in the control group spent a greater proportion of the total follow-up time on endocrine therapy (49% vs. 59%, p < 0.001). Over a median follow-up of 15.6 months, the rates of locoregional control (99% vs. 100%) and overall survival (99% vs. 100%) were similar between the two groups.
Conclusion: In this retrospective study with short follow-up, ATT followed by PBI produced comparable short-term adverse event profiles and recurrence rates, suggesting that PBI is a reasonable option following limited OBS.