Abstract PO4-23-05: Magnetic lymphatic tracing for omission of sentinel lymph node biopsies in mastectomy patients: a community cancer center experience

Abstract

Abstract Background Patients with ductal carcinoma in situ (DCIS) and patients undergoing risk reduction mastectomy traditionally undergo sentinel lymph node biopsy (SLNB) at the time of mastectomy to complete axillary staging were invasive malignancy to be identified on final pathology. About 10% of patients with DCIS undergoing mastectomy will have invasive disease on final pathology; thus, about 90% would be able to avoid SLNB. Standard lymphatic mapping for SLNB includes a combination of radioisotope and blue dye, which have a short half-life. Superparamagnetic tracers, such as Magtrace®, are non-inferior to this standard and remain active for several weeks, allowing many patients to avoid SLNB in the setting of mastectomy. Reducing SLNB may also reduce associated risks with SLNB such as hematoma, seroma, and subsequent lymphedema. Objective We hypothesized using Magtrace® would reduce the number of SLNB in patients undergoing mastectomy for DCIS or risk reduction. Consequently, this would reduce the number of SLNB-associated complications. We report a community cancer center experience with Magtrace® for omission of SLNB in select mastectomy patients. Methods This was a retrospective review of 52 female patients with DCIS or known genetic predisposition undergoing mastectomy. Magtrace® was injected ipsilateral to DCIS or bilateral for prophylactic mastectomy patients. Our primary outcome was rate of return to the OR for delayed SLNB. Secondary outcomes included post operative complications within 30 days of surgery and OR time. We compared outcomes to a control group of 28 women undergoing mastectomy for DCIS or risk reduction who underwent SLNB at their index operation. Continuous variables were reported using median and interquartile range (IQR) and were compared using the Mann-Whitney U-test. Categorical data were reported using frequency and percent; they were compared using Pearson’s Chi-Square or Fisher’s Exact test, as appropriate. Alpha was set to 0.05 to determine statistical significance. Results There were a total of 80 patients (52 Magtrace®, 28 control). Median age of Magtrace patients was 49.5 (IQR 40-60.75) vs. 54.5 (IQR 48-65) years for the controls. 57.7% of Magtrace® patients underwent mastectomy for DCIS vs. 89.3% in the control group. 8 Magtrace® patients (15.4%) had invasive ductal carcinoma on final pathology and 7 of those patients underwent SLNB and none were positive for metastatic disease. Of these, 6 patients underwent mastectomy for DCIS. Average number of sentinel lymph nodes was 1.57 in Magtrace® patients and 1.60 in the control patients. Rates of post operative complications were similar between the groups, including hematoma, seroma, surgical site infection, skin necrosis. OR times were also similar with median OR time 202 minutes (min) for the Magtrace® group vs. 195 min for the control group. Conclusion Use of Magtrace® avoided SLNB in 84.6% of our patients. We found no difference in rates of postoperative complications or operative times in patients using Magtrace® for omission of SLNB at time of mastectomy compared to the control group. Our findings suggest SLNB can be avoided in a majority of patients undergoing mastectomy for DCIS or risk reduction in the setting of genetic predisposition. Table. Citation Format: Mia Samaha, Barbara Wexelman, Anne Kurtizky, Kathleen Raque, Angie Fellner. Magnetic lymphatic tracing for omission of sentinel lymph node biopsies in mastectomy patients: a community cancer center experience [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-23-05.