Pathologic complete remission of cytologically proven axillary node metastases may be a strong prognostic factor in HER2-positive breast cancer

21149 Background: Preoperative chemotherapy has become one of the standard modes of treatment in patients with breast cancer, and pathologic complete remission (pCR) thus obtained has become an important prognostic factor. However, the number of cells in the main lesion is enormous and changes over time in a heterogeneous manner. Thus, time and individual differences in sensitivity influence the acquisition of pCR, and questions about the coincidence with the effects of metastatic lesions also remain. On the other hand, although pCR of axillary lymph node metastasis lesions with relatively lower numbers of the cells is considered one of the best surrogate prognostic markers, evaluation criteria have not yet been established because definitive preoperative diagnosis is difficult. In our department, preoperative axillary cytodiagnosis has been conducted in all surgical breast cancer cases. In this study, we investigated pCR of the axillary lymph nodes (ALN- pCR) in cytologically proven axillary node metastasis cases. Subjects and Methods: ALN-pCR, DFS, and OS were investigated in 52 surgical breast cancer cases (observation period: 15–52 months; medial level: 28 months) positive for cytological axillary metastasis and received preoperative chemotherapy (AC-Paclitaxel) during the period from 2002 to 2005. Results: ALN-pCR was found in 21 of 52 cases (40.4%). Rates of disease-free survival (DFS) at 36 months in ALN-pCR and non-ALN-pCR cases were 85.0% and 42.3% (P=0.031) and those of overall survival (OS; 48 months) were 100% and 87.9% (P=0.353), respectively. DFS (36 months) was very favorable 100% in ALN-pCR cases that obtained the effect of 1b or higher on evaluation of the main lesion effect and ALN-pCR cases with Her2-positive results on sub-type analysis. Conclusions: ALN-pCR of cytologically proven axillary node metastasis was indicated to be a prognostic factor in cases of breast cancer. Especially, its importance was demonstrated in HER2-positive breast cancer. From these findings, HER2-positive and cytologically axillary lymph node-positive cases were considered the best indications for preoperative chemotherapy. No significant financial relationships to disclose.