Abstract P2-12-12: The effect of Neoadjuvant Chemotherapy in reducing the need for axillary lymph node dissection in HR+/HER2- node positive breast cancers

Abstract Background In recent years, indications for neoadjuvant treatment (NAC) have been extended to patients with operable disease at diagnosis and it is increasingly being used in patients to reduce extent of axillary involvement and allow for more limited surgery in the breast and axilla. The increasing use of this therapy however has raised questions about optimal surgical exploration of the axilla post-chemotherapy. In this study therefore, we aimed to analyze the effect of NAC in reducing the need for axillary lymph node dissection (ALND), regardless of pathologic nodal status, in those who present with clinically node positive disease at diagnosis. Methods We sampled the National Cancer Database (NCDB) (2004-2016) for female patients with hormone receptor (HR) positive [estrogen receptor (ER) positive and/or progesterone receptor) (PR) positive], human epidermal growth factor receptor 2 (HER 2) negative, clinically node positive breast cancers. We then performed a multivariate logistic regression analysis to evaluate associations between chemotherapy regimen, disease, demographic, and geographic characteristics with the patients undergoing ALND. Statistics were performed using SPSS version 28.0 (190). Results N= 134704 female patients were included in the analysis; 79.2% Caucasian, mean age 59.13 years (SD = 13.95). Receiving NAC was associated with lower odds of undergoing ALND (OR = 0.849, 95% CI = 0.822 - 0.879, p <0.001) as compared to adjuvant chemotherapy (AC). On multivariate analysis, patients younger than 50 years old (ref, p = 0.005), black (OR = 0.824, 95% CI = 0.788 - 0.862, p <0.001), and uninsured (ref, p<0.001) were associated with lower odds of undergoing ALND as compared to their counterparts. In contrast, receiving care at Integrated Network Cancer Programs (OR = 1.182, 95% CI = 1.107 -1.261, p < 0.001) and residing in the Pacific region (OR = 1.519, 95% CI = 1.402 - 1.646, p < 0.001) was associated with a higher odds of patients undergoing ALND as compared to their counterparts. Conclusion Our findings indicate that for HR+/HER2-, node positive breast cancer, receiving chemotherapy in the neoadjuvant setting is associated with lower odds of ALND compared to when chemotherapy is received adjuvantly. Further studies exploring the effect of NAC on the nodal status post operatively, would help strengthen our findings. Additionally, while the use of chemotherapy remains a clinical decision, our study highlights that disparities in terms of sociodemographic and geographic factors may influence the receipt of such treatment in this cohort of patients. Citation Format: Iktej Singh Jabbal, Diana Saravia, Marita Yaghi, Nadeem Bilani, Leah Elson, Hong Liang, Zeina Nahleh. The effect of Neoadjuvant Chemotherapy in reducing the need for axillary lymph node dissection in HR+/HER2- node positive breast cancers [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 P2-12-12.