Omission of Sentinel Lymph Node Biopsy in Breast Cancer: A Real-World Validation of the Patient Populations of the SOUND and INSEMA Trials.

backgroundTreatment guidelines recommending omission of axillary surgery in breast cancer are largely based on the SOUND and INSEMA trials. However, the extent to which their study populations represent real-world patients remains unclear. We aimed to evaluate the real-world applicability and external validity of these trial populations. MATERIALS AND

methodsAll consecutive patients treated for early breast cancer at a single university hospital between 2010 and 2018 were included. Patients with clinically node-negative disease were identified, and eligibility according to the SOUND and INSEMA inclusion criteria was determined. Clinicopathologic characteristics were compared between trial-eligible real-world patients and published trial populations.

resultsA total of 2787 consecutive patients with clinically negative axilla were included; 71% (1982/2787) fulfilled the INSEMA and 52% (1461/2787) the SOUND trial eligibility criteria. Patients eligible in the SOUND trial were largely representative of real-world patients in terms of clinicopathologic characteristics. In contrast, the INSEMA trial appeared more selected, with a higher proportion of biologically favorable tumors. Both trials predominantly included patients with small (< 2 cm) luminal breast cancers. Patients with larger tumors and more aggressive subtypes were underrepresented.

conclusionThe SOUND and INSEMA eligibility criteria are broadly applicable to real-world patients with small luminal breast cancers. However, differences between trial populations and real-world patients highlight the need for careful consideration when applying SLNB omission beyond these lower-risk subgroups.