26 A Nomogram for Predicting High Axillary Disease Burden in Patients With Localized HR+, HER2-Negative Breast Cancer Following Neoadjuvant Chemotherapy

Background

Assessment of cancer burden in the axilla is a critical step in the management of patients with breast cancer. The rate of pathological complete response following neoadjuvant chemotherapy is very low in hormone receptor (HR)–positive, HER2-negative patients. Consequently, subjecting all patients with residual axillary disease on sentinel lymph node biopsy (SLNB) following neoadjuvant chemotherapy to axillary lymph node dissection (ALND) results in overtreatment and morbidities such as lymphedema. Therefore, there is a need to stratify patients based on predicted axillary disease burden to personalize axillary management.

Materials and Methods

A retrospective chart review was conducted of patients with localized HR-positive, HER2-negative breast cancer who received neoadjuvant chemotherapy followed by surgery from 2007 to 2024 (n=167) at UT Southwestern and Parkland hospitals. Variables investigated included age at diagnosis, race, clinical T stage, clinical N stage, clinical grade, posttherapy T stage, posttherapy grade, lymphovascular invasion, Ki-67 value pre- and post treatment, type of surgery, number of sentinel lymph nodes examined, number of positive sentinel lymph nodes, percentage of positive sentinel lymph nodes, whether greater than 50% of sentinel lymph nodes were positive, number of nodes removed by axillary dissection, tumor size, and multicentricity. The outcome variable was whether there were more than 3 total positive lymph nodes (of nodes positive during SLNB and ALND), as a surrogate for high axillary disease burden. Multivariable logistic regression with stepwise selection was performed to identify significant variables.

Results

The 3 variables significantly associated with high axillary disease burden were lymphovascular invasion (OR, 3.38; P = .023), number of positive sentinel lymph nodes (OR, 2.94; P <.001), and having greater than 50% of examined sentinel lymph nodes positive (OR, 15.43; P <.001). Based on the final logistic regression model, we have developed a nomogram for predicting the probability of having more than 3 total positive lymph nodes following neoadjuvant chemotherapy.

Conclusions

Developing nonsurgical approaches for characterization of axillary burden in these patients may enable identification of a subset of patients with low axillary disease burden who may be effectively managed without axillary dissection; such a need is particularly acute in patients with estrogen receptor–positive breast cancer since the probability of achieving nodal complete response following neoadjuvant chemotherapy is very low. This nomogram may serve as an additional aid in identifying patients with HR-positive, HER2-negative breast cancer with high axillary disease burden following neoadjuvant chemotherapy who may need ALND, while patients with low axillary disease burden may be considered for surgical de-escalation. Future studies are warranted to validate this nomogram in independent cohorts.