Abstract P1-01-07: Factors predicting a lower likelihood of residual nodal disease in clinically-node positive patients undergoing sentinel node surgery after neoadjuvant chemotherapy for breast cancer
Authors: Cabioglu Neslihan , Karanlık Hasan , Igci Abdullah , Muslumanoglu Mahmut , Tukenmez Mustafa , Emiroglu Selman , Ozkurt Enver , Onder Semen , Saip Pinar , Eralp Yesim , Aydiner Adnan , Yavuz Ekrem , Ozmen Vahit 
Published: March 2022

Background: Residual nodal disease at the completion axillary lymph node dissection (ALND) has been reported in over 60% in patients with a positive sentinel lymph node biopsy (SLNB) after neoadjuvant chemotherapy (NAC). This study aimed to explore whether any clinical or histopathological characteristics of patients may be associated with a lower likelihood of having non-SLN metastasis at ALND. Methods: Between January 2004 to January 2021, 459 patients with cT1-4/N1-3 underwent ALND due to a positive SLNB after NAC. Demographic, clinical and histopathological characteristics of patients were analyzed to predict the non-SLN metastasis at ALND. Sentinel lymph node ratio was defined as the ratio of the number of positive SLN to the total excised SLNs. Results: Median age was 47 (21-84). Of those, the majority of the patients had cT1-2 (67.8%) and cN1 disease (78.1%), whereas 76.5% of tumors were invasive ductal carcinoma. The frequency of non-SLN metastases according to the tumor subtypes were 59.5% in luminal A, 73.8% in HER2(-) luminal B, 60.3% in HER2(+) luminal B, 66.7% in non-luminal HER2(+), and 66.7% in triple negative breast carcinoma. Of those with removal more than 2 SLNs, having 1 positive SLN, or breast pathologic complete response, or cT1-2 disease , or a SLN ratio &lt;50% or low volume metastatic disease including isolated tumor cell (ITC)/micrometastasis were statistically less likely found to have a non-SLN metastasis (p&lt;0.05). Factors associated with a non-SLN involvement less than 40% were a SLN ratio &lt;50% (39.2%) and low volume metastatic disease (36.4%). Multivariate logistic regression analysis revealed a decreased likelihood for non-SLN metastasis at ALND for patients with cT1-2 (OR= 0.45; 95% CI: 0.25-0.82; p=0.009), ITC and micrometastasis (OR=0.24; 95% CI: 0.09-0.65; p=0.006), and a SLN-ratio &lt;50% ((OR=0.15; 95% CI: 0.08-0.26; p&lt;0.001). A subgroup of patients with cT1-2/N1 having a SLN ratio &lt;50% or ITC/micrometastasis were found to have 25.9% and 28.6% non-SLN positivity at ALND, respectively. Conclusions: In patients with a positive SLN after NAC, the likelihood of having residual disease at ALND was high across all tumor subtypes and clinical patient and tumor characteristics. However, the residual nodal disease rate was found to be lower than 30% in carefully selected patient subgroups with cT1-2/N1 along with ITC/micrometastasis or a SLN ratio &lt;50% (Table 1) . These results suggest omission of ALND could be considered in meticulously selected patients with cT1-2 and low volume metastatic disease as long as axillary radiation and effective systemic treatment provided Table 1. Factors associated with non-SLN metastasis at ALND

FactorsOR(95%CI)p-valuecT0.009*1&20.45(0.25-0.82)3&4Reference (1)SLN Status0.006*ITC and micrometastasis0.24(0.09-0.65)MacrometastasisReference (1)SLN-Ratio (%)&lt;0.001*&lt;50%Reference(1)≥50%0.15(0.08-0.26)*:p&lt;0.05, Logistic regression(enter method), OR:Odds Ratio; Dependent variable:Non-SLN positivity

Citation Format: Neslihan Cabioglu, Hasan Karanlık, Abdullah Igci, Mahmut Muslumanoglu, Mustafa Tukenmez, Selman Emiroglu, Enver Ozkurt, Semen Onder, Pinar Saip, Yesim Eralp, Adnan Aydiner, Ekrem Yavuz, Vahit Ozmen. Factors predicting a lower likelihood of residual nodal disease in clinically-node positive patients undergoing sentinel node surgery after neoadjuvant chemotherapy for breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-01-07.