Abstract PO5-23-04: Clinical utility of sentinel lymph node biopsy in women ≥ 70 years with early breast cancer – an international, retrospective multi-center cohort study

Abstract Introduction Traditionally, sentinel lymph node biopsy (SLNB) has been used to stage the axilla in early breast cancer (EBC) to guide adjuvant treatment recommendations. Following advances in tumor biology understanding, targeted systemic therapies and genomic testing, with increasing de-escalation of axillary surgery, its role may be less critical especially in selected groups of women. Aims Evaluate clinical utility of SLNB in adjuvant treatment recommendations for women ≥ 70 years with EBC. Methods Retrospective cohort study of women ≥ 70 years with cT1-2N0 EBC undergoing primary surgery and SLNB between 01/2017-12/2022 at The Royal Marsden Hospital (RMH), University Hospital Zurich (USZ) and Seoul National University Hospital (SNUH) in the United Kingdom, Switzerland and South Korea respectively. Simple descriptive statistics and non-parametric tests were performed as appropriate. Results A total of 884 patients were included in the analysis, with 584 patients from RMH, 148 from USZ and 152 from SNUH. The median age was 75 (IQR 72-79) years. Most cancers were invasive ductal (82.9%), grade 2 (61.4%), hormone receptor (HR) positive/HER2 negative (82.9%) with a median tumor size of 17 (IQR 4-50) mm. SLNB was positive in 116 (13.1%) patients. Of these 116 patients, 20 (17.2%) had completion ALND; 7/20 had further RT up to levels 3 25/96 had no further treatment, and 71/96 patients had loco-regional axillary RT (8/71 had RT to levels 1 0.0001). Axillary RT was more likely to be administered at SNUH and less likely at RMH (p 0.0001). The multidisciplinary team (MDT) recommended adjuvant chemotherapy (AC) in 146 (16.5%) patients and 100 received it. Of those with a positive SLNB (n=116), AC was recommended in 35, and received by 29. Recommendation for AC was significantly associated with younger age (p=0.021), fewer comorbidities (p=0.003), higher tumor grade (p 0.0001), increased tumor size (p 0.0001), HR negative status (p 0.0001), high genomic risk profile (p 0.0001) and positive SLNB status (p 0.0001), but not center (p=0.497). A subgroup analysis of 505 patients with cT1N0, HR+/HER2- EBC, representing a more favorable prognosis group, was performed. Here, 52/505 (10.3%) patients had positive SLNB, of whom 11 had no further axillary treatment, 9 underwent ALND and 32 axillary RT, where 4/9 could have been spared ALND and 28/32 axillary RT as per international guidelines mentioned above. AC was recommended in 26/505 (5.15%) women and 23 received it. AC was not recommended in 39/52 (75%) cases, despite a positive SLNB. MDT recommendation for AC was associated with grade 3 (p 0.0001), multifocal disease (p=0.021), positive SLNB status (p 0.0001), high genomic risk profile (p 0.0001), lower age (p=0.044), fewer co-morbidities (p=0.001) and center (p=0.007) with SNUH being more likely than the other 2, but not ethnicity (p=0.130); AC receipt was associated with the same factors except age (p=0.347). Conclusions Real-world data demonstrates axillary overtreatment despite evidence of the safety of de-escalation of axillary management in EBC. Only a small proportion of women ≥ 70 years with EBC had positive SLNB that may influence adjuvant treatment recommendations, especially with favorable prognosis tumors. In such cases, where clinical morbidity and financial burden of SLNB may outweigh the benefits, a nuanced discussion for opting in SLNB rather than routine performance should be considered. Citation Format: Radhika Merh, Denise Vorburger, Ji-Jung Jung, Han-Byoel Lee, Marios Tasoulis. Clinical utility of sentinel lymph node biopsy in women ≥ 70 years with early breast cancer – an international, retrospective multi-center cohort study 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 PO5-23-04.