Review of Variables Associated With Positive Surgical Margins Using Scout Reflector Localizations for Breast Conservation Therapy

Objective To evaluate factors contributing to positive surgical margins associated with reflector guidance for patients undergoing breast conserving therapy for malignancy. Materials and Methods A retrospective IRB-approved review of our institutional database was performed for malignant breast lesions preoperatively localized from January 1, 2018 to December 31, 2020. The following data was recorded using electronic medical records: lesion type and grade, lesion location, reflector and wire placement modality, use of intraoperative ultrasound, margin status, patient age, family history, BMI, and final pathology. Statistical analysis was performed with univariate summary statistics and logistic regression. P Results A total of 606 image-guided pre-surgical localizations were performed for lumpectomies of breast malignancies. A total of 352 of 606 (58%) wire localizations and 254 of 606 (42%) SCOUT reflector localizations were performed. Sixty out of 352 (17%) of wire-localized patients had positive surgical margins, whereas forty-eight out of 254 (19%) of reflector-localized patients had positive surgical margins. (OR = 1.12, P value: .59). For reflector guided cases, the use of intraoperative ultrasound (IOUS) was associated with decreased positive margin status (OR = 0 .28, 95% CI = [0.14, 0.58]) while in situ disease was associated with increased positive margin status (OR = 1.99, 95% CI = [1.05, 3.75]). No association between modality used for localization (mammography vs. ultrasound) and positive margin status was observed (OR = 0.63, 95% CI = [0.33, 1.19]). No association between positive margins and age, family history, tumor location and BMI was observed. Conclusion For reflector guided surgeries, the use of IOUS was associated with decreased positive margins, by contrast the presence of ductal carcinoma in situ was associated with increased positive margins. There was no statistically significant difference in surgical outcomes for reflector-guided localization compared to wire localizations of the breast.