The Era "or Error" of Second Localization Procedures

Background: Clips placed after core needle biopsy are often several millimeters to centimeters from the biopsy cavity. Radiofrequency and radar (R) localization involve a second localization procedure based on the prior clip placement, potentially compounding the distance from the area localized to the original biopsy site. Fluoroscopic intraoperative neoplasm detection (FIND) obviates the need for a second localization by using intraoperative fluoroscopy to localize the original biopsy clip. We hypothesized that intraoperative localization using FIND is feasible and may result in fewer positive margins. Methods: A retrospective review was performed of patients with nonpalpable malignancy who underwent partial mastectomy from September 2016 to August 2023. Results were compared between patients who underwent R localization vs. FIND. The Pythagorean theorem was used to calculate the distance in space between the biopsy clip and the R localization device. Chi-square was used to calculate the two-tailed p value. Results: We identified 219 patients: 161 localized with FIND and 55 with R. Three percent (6 out of 161) of the patients with FIND and 12% (7 out of 55) of the patients with R had positive margins (p=0.01). The average distance between the R device and biopsy clip in patients with positive margins was 19.1 mm, and with negative margins, it was 12.45 mm (p=0.09). Conclusions: The positive margin rate with R localization was significantly greater than with FIND. The positive margin rate trended toward increased distance from the localization device to the biopsy clip. Eliminating the second localization decreases painful procedures for the patient and may result in improved tumor-free margins.