Background: The axillary status after neoadjuvant chemotherapy (NACT) is an important prognostic factor. Complete axillary downstaging (CAD) occurs in up to 20-30% of the patients, however, sentinel node biopsy after NACT is not recommended in patients with initial axillary nodal involvement and complete axillary response after NACT. Our aim was to investigate predictive factors of CAD after NACT to identify patients who could avoid an unnecessary axillary dissection. Patients and methods: From January 2004 to December 2008, 256 consecutive patients were diagnosed with invasive breast cancer and received NACT and breast surgery at our institution. Patients were eligible for this analysis if they met the following inclusion criteria: clinically and/or cytologically proven metastatic axillary nodes; complete axillary response after NACT; and complete axillary dissection after systemic treatment. CAD was defined as pN0 (isolated tumor cells and micrometastasis were excluded). Univariate and multivariate analyses were performed to assess the association between CAD and either tumor characteristics or intrinsic cancer subtypes.

Results: 84 patients were included. Median age was 51.64 years. 75 (89,3%) received anthracyclines-and taxanes-based CT and 11 (13%). 38 (45,2%) had cytologically proven metastatic axillary nodes at diagnosis. According to intrinsic cancer subtypes, 22 (26%) were classified as HER2 positive, 17 (20,2%) as triple negative (ER, PR, and HER2 -), 6 (7,1%) as luminal A [estrogen receptor positive and/or progesterone receptor positive and (Ki67 < 20% and histological grade 1 or 2)], and 23 (27,4%) as luminal B [estrogen receptor positive and/or progesterone receptor positive and (Ki67 ≥20% or histological grade 3)]. In the univariate analysis, HER2 positivity (p=0,002) and neoadjuvant treatment with trastuzumab (p=0,019) were significantly associated with CAD. In the multivariate analysis only HER2 status maintained statistical significance (p=0,003). Among luminal A, luminal B, and triple negative tumors, complete axillary response after NACT did not significantly predict CAD.

Conclusions: In our cohort of breast cancer patients, HER2 status is an independent predictive factor of CAD after NACT. Clinical trials, probably according to specific breast cancer subtypes, are required to identify patients with initial axillary metastatic involvement who could avoid an axillary dissection after systemic therapy.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P2-09-27.