Abstract PO3-12-09: De-Escalating Extent of Sentinel Lymph Node Biopsy in Patients with Ductal Carcinoma in Situ Undergoing Mastectomy

Abstract Background: Sentinel lymph node (SLNB) biopsy for axillary staging in patients (pts) with ductal carcinoma in situ (DCIS) undergoing mastectomy is debated due to low positivity rate and potential morbidity. Standard SLNB entails removing all LNs with a radioactive count 10% of the most radioactive node, contain blue dye or are palpably suspicious. In this study, we hypothesize that judicious SLNB with attempt to remove only the SLN with the highest radioactive count provides sufficient pathologic information while minimizing morbidity. Method: A single institution prospective database was retrospectively reviewed to identify women with core biopsy showing DCIS (cTis) who underwent mastectomy and SLNB between 2010–22. Pt characteristics, number of SLNs retrieved, pathologic results and long-term upper extremity complications were collected. Results: A total of 743 LN's were removed in 324 pts. Median IQR age was 62 51–70 years. Dual tracer technique, with Technetium-99m labeled radiocolloid and blue dye, was used in 311 (96%) pts, whereas single agent (radioisotope or blue dye alone) was utilized in 9 (2.8%) and 4 (1.2%) pts respectively. Median IQR number of SLN removed was 2 1-3 (range 1-9). In 99% of cases, the SLN with the highest radioactive count was identified among the first 3 dissected LNs. Final pathology revealed upstaging to invasive cancer in 27.5% (n=89) of the breasts and nodal positivity in 1.9% (n=6) of the patients. In all 6 cases, metastatic disease was identified in the LN with highest radioactive count among the LNs retrieved. No additional metastatic nodes were identified after 3 SLN had been removed. At median follow-up of 57 (range 28-87) months, 8.3% (n=27) of pts complained of long-term upper extremity symptoms. 7.1% (23 pts) were referred to physical therapy for symptoms such as swelling, fullness, heaviness, stiffness or sensory discomfort in the upper extremity and/or axillary cording. Long-term upper extremity complications were higher when 3 SLNs compared to 3 SLNs were removed (10.4% vs 6.5%, p=0.005). Conclusion: In this cohort of pts with DCIS (cTis) undergoing mastectomy who had upstaging on final pathology to invasive cancer with LN involvement, the SLN with the highest radioactive count provided sufficient information for axillary staging. Acknowledging that the “hottest” LN is not always the first one removed, these data support an increased likelihood of developing long-term complications when more than three SLNs are removed. Rather than comprehensive removal of all SLNs meeting the standard “10% rule,” prioritizing the sequence of removal to the highest count provides the same prognostic information with reduced morbidity. Patient and lymph node characteristics Citation Format: Adil Ayub, Kazim Senol, Makris Eleftherios, Michael Cowher, Ronald Johnson, Kristin Lupinacci, Qurat Ul Ain Sabih, Jennifer Steiman, Emilia Diego, Priscilla McAuliffe, Atilla Soran. De-Escalating Extent of Sentinel Lymph Node Biopsy in Patients with Ductal Carcinoma in Situ Undergoing Mastectomy 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 PO3-12-09.