Abstract PS4-11-06: A comparison of mortality in SOUND matched population - A single institution experience

Abstract Introduction: Sentinel lymph node biopsy (SLNB) is the standard of care for axillary staging in early-stage breast cancer (EBC). Nodal positivity in T1 disease remains low. The early results of the SOUND trial have demonstrated that eliminating SLNB in patients with cT1 cN0 disease is not inferior and may potentially lead to further de-escalation of axillary surgery in EBC without compromising the oncological safety. This study aims to compare mortality in the given cohort. Methodology: A retrospective study using single unit data from October 2008 to August 2023. All invasive breast cancer up to 2 cm in diameter, with no involvement of the axillary nodes, and a planned breast-conserving surgery and radiation were included in the study in line with SOUND trial. Pre-operative axillary ultrasonography was performed in all these patients as part of their preoperative assessment to confirm cN0 status and any suspicious nodes were then subjected to FNA. Patients’ demographics, disease distribution, nodal positivity were studied along with breast cancer specific and overall mortality. Results: Out of 662 patients in the given period, 198(29.9%) had Grade 1 disease, 365(55.1%) had Grade 2 and 99(14.9%) Grade 3 disease. Mean age of the entire cohort was 61.1, the mean tumour size was 12.31mm. 65(9.8%) patients had positive sentinel nodes out of which 53(8%) had pN1 disease, 6(0.9%) had pN2 disease, 6 had micro-metastasis only. 41(63.07%) patients were screen detected cancers, and 21(32.3%) patients were symptomatic. 56(86.1%) patients were hormone receptor positive type, 3 (4.61%) patients had triple negative and 3(4.61%) had HER2 positive disease. Most common type of cancer noted was invasive ductal in 58(89.2%) patients and 3(4.61%) of them had invasive lobular carcinoma and remaining 1(1.53%) patient had tubular carcinoma. Mean Follow up of 66.3 months, while 3 out of 65 data lost in follow up. A total of 2 loco-regional recurrence (in breast), 1 had contralateral breast cancer and 2 had distant metastasis. The mortality rate in this subset of patients was 1.9% vs 2.6% in SOUND trial. Conclusion: Our study shows that nodal positivity 9.8% while 14% in SOUND trial with comparable N2 disease (0.9% vs 0.6%). SOUND had a lower proportion of micro-metastasis (5.1% vs 9.2%) than our study with comparable mortality rates (2.6% vs 1.9%). The mortality rates are similar in both node negative and node positive groups adding weight to the argument on further axillary de-escalation in EBC. Our study has limitation of small numbers but aligns well with SOUND and the long-term data of the trial will possibly make way for changes in current practice of routine SLNB in low risk EBC. Citation Format: C. Gavisiddappa, R. Parmeshwar. A comparison of mortality in SOUND matched population - A single institution experience [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS4-11-06.