Abstract OT1-20-01: SentiNot 2.0: Avoid unnecessary Sentinel Lymph Node Biopsies in women with DCIS

Abstract Background Approximately 15-30% of women with a preoperative diagnosis of ductal carcinoma in situ (DCIS) will be diagnosed with invasive cancer (IBC) on specimen pathology. Risk of upgrade, and impairment of lymphatic outflow after breast surgery, mainly mastectomy, are drivers for upfront sentinel lymph node dissection (SLND). In the SentiNot feasibility study, marking the SLN by superparamagnetic iron oxide nanoparticles (SPIO) injection during primary surgery minimized unnecessary SLNDs, allowing for delayed SLND (d-SLND) only in those with IBC up to 50 days after primary surgery. This policy resulted in that 78.3% study participants avoided upfront SLND. In the d-SLND setting, SPIO detection outperformed the isotope (98.5 vs 60.6%), regardless of type of breast procedure. Incremental healthcare costs were reduced by 8.5% (485 USD per patient) for the entire trial population (ref 1). Prospective Clinical Trial Design SentiNot 2.0 (ClinicalTrials.gov Identifier: NCT04722692), is currently accruing data, powered to examine the detection rate of SPIO over isotope±blue dye during d-SLND. Trial candidates are: patients with a diagnosis of high-risk DCIS/pLCIS (mass-lesions, microinvasion, grade 3, grade 2 >20mm) regardless of type of breast surgery, and patients with planned breast surgery that precludes safe and accurate axillary mapping at a d-SLND (extensive oncoplastic breast conservation, tumors of the axillary tail and mastectomy). In d-SLND, study patients receive isotope±blue dye and within-patient-randomization is performed for which detection method to start with (SPIO-first vs. isotope-first). The trial is stratified for mastectomy and breast conservation. Secondary outcomes are nodal concordance (SPIO vs. isotope) at d-SLND, quality-of-life and health-economy outcomes. Present and Planned Accrual Total target accrual is 500 d-SLNDs. Insofar, 360 women have been included at six different sites in Sweden, Hong Kong, and the USA. Currently, data accrual and institution recruitment is active and expanding. For more information about the trial please refer to ClinicalTrials.gov Identifier: NCT04722692. For discussion regarding potential participation contact dr Andreas Karakatsanis (andreas.karakatsanis@surgsci.uu.se). Citation Format: Eirini Pantiora, Staffan Eriksson, Lida Pistiolis, Roger Olofsson Bagge, Gyula Nagy, Alastair M. Thompson, Vivian Man, Ava Kwong, Andreas Karakatsanis, Fredrik Wärnberg. SentiNot 2.0: Avoid unnecessary Sentinel Lymph Node Biopsies in women with DCIS [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT1-20-01.