Comparison of clinical characteristics between ACOSOG Z0011-eligible cohort and sentinel lymph node-positive breast cancer patients in Hong Kong.

Introduction: The American College of Surgeons Oncology Group (ACOSOG) Z0011 trial resulted in de-escalation of axillary surgery among early-stage breast cancer patients with low-volume sentinel lymph node (SLN) disease undergoing breast-conserving surgery and radiation therapy. Nevertheless, the mastectomy rate in the Chinese population remains high. This study compared the clinical characteristics of the ACOSOG Z0011-eligible cohort with SLN-positive breast cancer patients in Hong Kong.

Methods: This retrospective analysis of a prospectively maintained database at a university-affiliated breast cancer centre in Hong Kong was performed from June 2014 to May 2019. The database included all patients with clinical tumour (T) stage T1 or T2 invasive breast carcinoma, no palpable adenopathy, one or two positive SLNs on histological examination, and no prior neoadjuvant systemic treatment. Comparisons were made between the mastectomy and breast-conserving treatment groups in our cohort, along with the sentinel-alone arm in the ACOSOG Z0011 trial.

Results: One hundred and seventy-one patients met the inclusion criteria: 112 underwent mastectomy and 59 underwent breast-conserving treatment. Our mastectomy group had higher prevalences of T2 tumours (P<0.001), lymphovascular invasion (P<0.001), and SLN macrometastases (P=0.004) compared with the ACOSOG Z0011 cohort. However, in our patient population, mean pathological size slightly differed between the mastectomy and breast-conserving treatment groups (2.2 cm vs 1.8 cm; P=0.005). Other histopathological features were similar.

Conclusion: This study demonstrated that clinicopathological features were comparable between SLN-positive breast cancer patients undergoing mastectomy and those undergoing breast-conserving treatment. Low-risk SLN-positive mastectomy patients may safely avoid completion axillary lymph node dissection.