Preoperative Predictive Factors of Positive Margin Status After Breast Conserving Therapy (BCT) with Intraoperative Radiation Therapy (IORT): A Retrospective Study of 400 Patients.

ABSTRACT

INTRODUCTION: Single-fraction intraoperative radiation therapy (IORT) has emerged as a therapeutic option in patients undergoing breast conserving therapy (BCT) for early stage breast cancer, often eliminating the need for postoperative external beam radiation therapy. However, if a positive margin is encountered after BCT, the patient will ultimately require external beam radiation therapy. The purpose of this study was to identify preoperative factors from patient demographics, preoperative workup, or biopsy results that may be predictive of postoperative margin status. MATERIALS AND METHODS: A retrospective chart review was performed on 396 patients who underwent BCT with IORT. Logistic regression models were utilized for statistical analysis. RESULTS: The majority of studied variables were similar; however, differences were noted for high-grade tumors, in situ status, and progesterone receptor-negative (PR-) tumors. Grade 3 tumors were significantly associated with positive margin status when compared with Grade 1 (odds ratio, 2.30; P = .036). PR- status tumors were found to be approximately 2 times more likely to have a positive margin (P = .028). Patients with in situ (stage 0) status tumors were 1.986 times more likely to have positive margins when compared with those with an invasive tumor (P = .030). CONCLUSIONS: Higher grade PR- tumors are at increased risk of having a positive margin, which should be taken into consideration when considering treatment with IORT.