Prospective feasibility study on delayed selective sentinel node biopsy for patients undergoing mastectomy for ductal carcinoma in situ.

e12567 Background: In patients with ductal carcinoma in situ (DCIS) undergoing total mastectomy, sentinel lymph node biopsy (SLNB) is typically performed during primary surgery to address the potential risk of invasive cancer. However, the likelihood of DCIS upgrading to invasive cancer is only 10–20%, leading to unnecessary SLNBs in most cases. This study evaluated the feasibility of SLN localization during primary surgery and its detection in secondary surgery if invasive cancer is diagnosed. Methods: This prospective study enrolled patients diagnosed with DCIS and scheduled for mastectomy between June 2023 and January 2025. Exclusion criteria included suspicious invasive findings on biopsy or imaging, suspected lymph node metastasis, prior axillary surgery, or pregnancy. Preoperative SLN mapping was performed using dye ± isotope, followed by intraoperative SLN localization with tagging sutures (Vicryl, later changed to Maxon) and surgical titanium clips (small, later changed to medium size). If invasive cancer was diagnosed postoperatively, secondary surgery was performed, and the primary outcome was the detection rate of localized SLNs during the second surgery. This feasibility study reports interim results due to impending deadlines. The study does not require a predefined sample size, as the primary goal is to assess practicality and safety. Results: A total of 66 patients were enrolled in the study between June 2023 and January 2025. Among them, 4 patients underwent intraoperative SLNB due to suspicious lymph node findings during surgery, but all were ultimately diagnosed with DCIS. Of the 66 patients, 6 (9.1%) were diagnosed with microinvasive cancer, and 9 (13.6%) were diagnosed with invasive cancer. During the primary surgery, SLN localization was performed on 1 node in 53 patients (85.5%) and on 2 nodes in 9 patients (14.5%). For the 9 patients diagnosed with invasive cancer, secondary surgery was performed with a median interval of 22 days from the primary surgery. In the initial two secondary surgeries, localized SLNs could not be identified. Upon review, it was determined that the Vicryl 3-0 sutures used for tagging might have been absorbed during the interval between surgeries. Subsequently, the protocol was adjusted to use Maxon, a slow-absorbing suture, and medium-sized surgical titanium clips. After this modification, the detection rate for localized SLNs in the remaining 7 secondary surgeries was 100%. No lymph node metastasis was observed in any of the secondary surgeries. Conclusions: This study demonstrates that SLN localization using simple and accessible techniques is a feasible approach in patients with DCIS undergoing total mastectomy. Although the detection rate in this single-center study was promising, further multicenter studies with larger sample sizes are warranted to confirm the reproducibility and generalizability of this approach. Clinical trial information: NCT05912569 .