Sentinel Lymph Node Positivity by Tumour Grade in Older Women With Breast Cancer: A Cross-Verified Retrospective Cohort Study

Abstract

Background: The Choosing Wisely campaign and several randomised trials have questioned the routine use of sentinel lymph node biopsy (SLNB) in older women with early-stage, hormone receptor-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer, given the low rate of axillary nodal involvement and its limited impact on adjuvant management in this population. Objective: To determine the rate of SLNB positivity in women aged ≥70 years with Grade 1, T1-T2, estrogen receptor (ER)-positive, HER2-negative invasive breast cancer, to compare this rate against Grade 2 and Grade 3 disease of similar stage and receptor profile, and to assess whether the data support selective omission of SLNB in this specific subgroup. Methods: We conducted a retrospective cohort study at a single UK breast unit. Patients who underwent SLNB between January 2015 and December 2020 were identified from hospital coding records and cross-linked, via hospital identifier, to a separate histopathology database, with age at surgery independently verified using linked admission dates rather than assumed from the histopathology record alone. Patients meeting Grade 1, T1-T2, ER-positive, HER2-negative criteria - including mucinous carcinoma and invasive ductal carcinoma (IDC) with a papillary component, given their comparably favourable low-grade biology - formed the primary study subgroup. Proportions are reported with 95% Wilson score confidence intervals. Results: Of 420 patients identified via hospital coding, 323 tumours in 319 patients formed the final, age-verified analytic cohort after cross-linkage and per-tumour verification. Within the ER-positive/HER2-negative population (n=243), the primary study subgroup - Grade 1, T1-T2 disease - comprised 39 patients (32 T1, 7 T2). SLNB was positive in 3 of 39 patients (7.7%; 95% CI 2.7-20.3%). Restricted to the same T1-T2, ER+/HER2- criteria, SLNB positivity rose with tumour grade: 7.7% in Grade 1 versus 19.8% (95% CI 13.9-27.5%) in Grade 2 and 13.7% (95% CI 6.8-25.7%) in Grade 3. All 39 patients were followed up for a minimum of five years and a maximum of eight years, with no axillary or locoregional recurrences observed. Conclusion: In women aged ≥70 years with Grade 1, T1-T2, ER-positive, HER2-negative breast cancer, SLNB positivity is low (7.7%) and notably lower than in Grade 2 or 3 disease of similar stage and receptor profile. These findings suggest that tumour grade should be incorporated into SLNB omission criteria, rather than relying on age and receptor status alone, and identify Grade 1 disease specifically as the most favourable candidate for selective SLNB omission. As a retrospective, single-arm estimate of nodal positivity rather than a comparative safety study, this work is best regarded as hypothesis-generating, and the case for omission should be confirmed in larger, prospective, multicentre cohorts with an appropriate comparator.