Abstract P3-05-32: Positive sentinel lymph node does not affect prognosis in T1 breast cancer patients who undergo breast conserving surgery with sentinel lymph node biopsy

Abstract

Backgrounds: The ACOSOG Z0011 trial revealed oncologic outcomes in patients who underwent breast conserving surgery (BCS) and sentinel lymph node biopsy only versus completion axillary dissection to be equivalent. It was also reported that axillary recurrence rate to be not different between axillary dissection group and SLNB only group, despite the positive rate of over 20% in non-sentinel lymph nodes. It led to suspicion that the role of SLNB in local control to be less significant than previously recognized. Currently trials such as SOUND trial and NAUTILUS trial are being conducted in cT1N0 breast cancer undergoing BCS to compare the outcomes between the current standard surgery and no axillary surgery. Purposes: This study aimed to investigate the factors associated with positive SLN in patients with T1 breast cancer, including T substages. We also evaluated the oncologic outcomes according to SLN positivity. Method: We retrospectively reviewed medical records of patients with pT1 breast cancer who underwent BCS including SLNB at Seoul National University Bundang Hospital from 2010 to 2015 (n=986). SLN positive was defined as one or more micro- to macro-metastasis in axillary lymph node specimen. Overall, regional, and systemic recurrence-free survival (RFS, RRFS, SRFS) and overall survival (OS) were estimated by the Kaplan-Meier analysis. Result: Of 986 patients, positive SLN was observed in 116 patients (11.8%). Regarding T substages, T1mic, T1a, and T1b gouprs showed SLN positive rate of 0%, 3.4%, and 8.5% respectively whereas T1c showed 15.3%. Multivariable logistic regression analyses revealed clinical T stage (OR 1.791, 95% CI 1.061-3.023, P=0.029), >C2 finding in preoperative axillary ultrasonograpy (OR 3.021, 95% CI 1.740-5.248, P< 0.001), usual histologic type including invasive ductal carcinoma, invasive lobular carcinoma, and metaplastic carcinoma confirmed in preoperative biopsy (OR 4.406, 95% CI 1.357-14.305, P=0.014) to be independent predictive factors for SLN positivity. The median follow-up period was 103.03 months. The 5 year RFS, RRFS, SRFS, and OS showed no statistical difference between SLN positive group and negative group. In multivariable Cox regression analysis, serum CEA level higher than 5ng/ml at diagnosis (HR 7.534, 95% CI 3.336-17.019, P=0.002) and Ki-67 level higher than 20% (HR 7.534, 95% CI 3.336-17.019, P< 0.001) were shown to be the independent prognostic factors for RFS. Conclusion: Our data implicates that patients with T1c breast cancer should undergo SLNB at all times presently, considering substantially higher SLN positive rate compared to other T1 substages (16.8% vs. 6.1%, P< 0.001) although no survival difference was observed between SLN positive group and negative group. Kaplan-Meier curve of recurrence-free survival and overall survival Kaplan-Meier curve of recurrence-free survival and overall survival Kaplan-Meier analyses revealed no difference of recurrence-free survival, overall survival between SLN-positive and SLN-negative group. Univariable and multivariable model for recurrence-free survival Higher Ki-67 expression, ER negativity, PR negativity, HER2 positivity were shown to be independent risk factors associated with shorter RFS. Multivariable analysis showed higher Ki-67 expression as the sole independent risk factor for shorter RFS. Citation Format: Hyoung Won Koh, Hee-Chul Shin, Eun-Kyu Kim, Eunyoung Kang. Positive sentinel lymph node does not affect prognosis in T1 breast cancer patients who undergo breast conserving surgery with sentinel lymph node biopsy. [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 P3-05-32.