Factors Influencing Axillary pCR in HER2+ Breast Cancer Undergoing NAC

Overview

This retrospective cohort study analyzed factors influencing axillary pathological complete response (pCR) in HER2-positive breast cancer patients undergoing neoadjuvant chemotherapy (NAC). The study highlights the potential to reduce unnecessary axillary lymph node dissections by identifying predictors of axillary pCR, enabling less invasive surgical approaches.

Background

Axillary management in breast cancer has shifted from radical lymph node dissection to more conservative techniques such as sentinel lymph node biopsy (SLNB) to reduce morbidity. In HER2-positive breast cancer, neoadjuvant chemotherapy combined with anti-HER2 agents achieves high rates of axillary pCR, allowing for the possibility of avoiding extensive axillary surgery. Recent guidelines recommend targeted axillary dissection (TAD) in selected patients, but criteria continue to evolve, especially for those with higher initial nodal burden. Identifying clinical and radiological predictors of axillary pCR is crucial to optimize surgical management and improve patient outcomes.

Data Highlights

The study included 60 women with HER2-positive breast cancer and axillary involvement treated with NAC followed by surgery. Imaging modalities used pre- and post-NAC included mammography/tomosynthesis, ultrasound, and MRI. Axillary radiologic complete response (rCR) was assessed primarily by ultrasound criteria. The cohort was stratified by initial axillary burden: low (≤3 positive nodes) and high (≥4 positive nodes). Key variables analyzed included age, tumor size, tumor grade, Ki-67 proliferation index, and radiologic response.

Key Findings

• Neoadjuvant chemotherapy combined with anti-HER2 therapy induced axillary pCR in a substantial proportion of patients, supporting less invasive axillary surgery.
• Axillary radiologic complete response assessed by ultrasound was a strong predictor of achieving axillary pCR.
• Patients with low initial axillary burden (≤3 positive nodes) had higher rates of axillary pCR compared to those with high burden (≥4 nodes), but selected high-burden patients achieving radiologic response may also avoid extensive dissection.
• Other factors influencing axillary pCR included younger age, smaller initial tumor size, higher tumor grade, and elevated Ki-67 index.
• Targeted axillary dissection (TAD) after NAC is feasible and may safely replace complete axillary lymph node dissection (ALND) in selected HER2-positive patients.

Clinical Implications

These findings support the use of comprehensive imaging assessment, particularly ultrasound, to evaluate axillary response after NAC in HER2-positive breast cancer. Incorporating radiologic response and clinical factors can guide surgical decision-making, potentially reducing the need for ALND and its associated morbidity. Adoption of less invasive techniques like SLNB or TAD in patients with favorable response may improve quality of life without compromising oncologic safety.

Conclusion

Axillary pCR in HER2-positive breast cancer patients undergoing NAC is influenced by initial nodal burden, radiologic response, and tumor biology. Careful patient selection based on these factors can facilitate less invasive axillary surgery, minimizing morbidity while maintaining effective cancer control.

References

1. García-Tejedor et al 2022 -- Axillary management in HER2+ breast cancer after NAC
2. ACOSOG Z1071 Study 2017 -- Avoiding ALND in patients with axillary pCR
3. Caudle et al 2016 -- Targeted axillary dissection feasibility
4. Zhang et al 2020 -- Axillary surgery omission in selected breast cancer cases