Abstract PS1-14: Impact of axillary dissection and patterns of care in patients with ypN1 triple negative breast cancer receiving regional nodal irradiation

Abstract

Abstract Background: The benefit of axillary lymph node dissection (ALND) in patients with pN1 disease on sentinel lymph node biopsy (SLNB) following neoadjuvant chemotherapy for invasive breast cancer in patients receiving regional nodal irradiation (RNI) is unclear, even in patients with high risk histologic features such as triple negative disease. We sought to determine any association of ALND with improved survival, as well as patterns of care in this cohort using the National Cancer Database (NCDB). Methods: The NCDB was queried for women ages 18-75 with cT1-3N1 and ypT0-T3N1M0 breast cancer that underwent definitive surgical resection with axillary staging followed by adjuvant regional nodal irradiation, with triple negative receptor status. Only patients who were treated from 2012 - 2015 were included for appropriate coding of the extent of axillary surgery. Overall survival was estimated using the Kaplan-Meier method and Cox proportional hazards models. An analysis of the number of lymph nodes removed, rate of RNI utilization, and rate of ALND was performed using the Wilcoxon rank-sum test, proportions of RNI utilization compared using the Chi-squared test, and correlation of these to year of diagnosis was evaluated with the Pearson correlation coefficient. Results: A total of 572 women were identified that met inclusion criteria. The median age was 53 (range 24-75) years. 67 (11.7%) of women had SLNB alone and 505 (88.3%) had ALND with or without SLNB. Four year OS was 66.7% in patients undergoing ALND compared to 70.6% in those that had SLNB alone (p = 0.47). Charlson-Deyo comorbidity index (CDCC) (p = 0.01) and clinical T3 stage (p = 0.03) were significantly associated with survival. After adjusting for age, histology, clinical and pathologic T-stage, and CDCC, there was no significant relationship between receipt of ALND and overall survival (OS), however CDCC (p = 0.01) and cT3 or pT3 (p = 0.02 and p =0.01) remained significantly associated with OS. The mean number of lymph nodes sampled from 2012 to 2015 increased from 11.68 to 13.46 (p = 0.07). The rate of RNI increased from 55.6% in 2012 of patients to 58.4% in 2015 (p = 0.6). The rate of ALND increased from 83.9% in 2012 to 90.8% in 2015 (p = 0.2). Pearson correlation coefficients between mean number of lymph nodes sampled, rate of RNI, and rate of ALND were 0.83. 0.13, and 0.95 respectively. Conclusions: There was no difference in overall survival between patients with cT1-3N1M0 and ypT0-3N1M0 triple negative breast cancer receiving SLNB compared to ALND with adjuvant RNI, even when adjusting for tumor size and comorbidities, which remained significant risk factors. There was a trend towards an increase in the mean number of lymph nodes sampled and increased utilization of ALND, though these failed to reach statistical significance. We await the results of the Alliance 011202 randomized trial to provide prospective guidance of the utility of ALND in this high risk subgroup. Table 1. Baseline Characteristics For Triple-Negative PatientsSLNB (n=67)ALND (n=505)Median Age (Years)5353Histology (n, %)Ductal61 (91%)452 (90%)Lobular2 (3%)15 (3%)Other4 (6%)38 (7%)T-Stage (n,%)cT111 (16%)73 (15%)cT234 (51%)290 (57%)cT322 (33%)142 (28%)CDCC (n,%)054 (81%)441 (87%)19 (13%)51 (10%)24 (6%)8 (2%)30 (0%)5 (1%)Mean CDCC0.250.16Facility Type (n,%)Community5 (7%)36 (7%)Comprehensive Community27 (40%)171 (34%)Academic/Research13 (19%)160 (32%)Integrated Network13 (19%)72 (14%)Other/Unknown9 (14%)66 (13%)Lymphovascular Invasion (%)32.84%32.48%Median Tumor Size (cm)3.63.3Median Nodes Examined412Median Nodes Positive12 Citation Format: Michael Kharouta, Nicholas Damico, Megan Miller, Eleanor Harris, Janice Lyons. Impact of axillary dissection and patterns of care in patients with ypN1 triple negative breast cancer receiving regional nodal irradiation [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS1-14.