Possibility of avoiding axillary lymph node dissection by immune microenvironment monitoring in preoperative chemotherapy for breast cancer

BACKGROUND: The diagnosis of metastasis by sentinel lymph node biopsy (SLNB) in early breast cancer surgery provides an accurate view of the state of metastases to the axillary lymph nodes, and it has now become the standard procedure. In the present study, whether omission of axillary lymph node dissection (ALND) after neoadjuvant chemotherapy (NAC) is possible by evaluation of tumor-infiltrating lymphocytes (TILs) before NAC in cases without metastasis on diagnostic imaging, but with metastasis on SLNB, was retrospectively investigated. METHODS: A total of 91 patients with resectable, early-stage breast cancer, diagnosed as cT1–2, N0, M0, underwent SLNB and were treated with NAC. A semi-quantitative evaluation of lymphocytes infiltrating the peritumoral stroma as TILs in biopsy specimens of primary tumors prior to treatment was conducted. RESULTS: In cases with a low number of TILs, estrogen receptor expression was significantly higher (p = 0.044), and human epidermal growth factor receptor 2 (HER2) expression was significantly lower than in other cases (p = 0.019). The number of TILs was significantly lower in cases in which the intrinsic subtype was hormone receptor-positive breast cancer (HRBC) (p = 0.044). Metastasis to axillary lymph nodes was significantly more common in HER2-negative cases and cases with a low number of TILs (p = 0.019, p = 0.005, respectively). CONCLUSIONS: Even if macrometastases are found on SLNB in cN0 patients, it appears that ALND could be avoided after NAC in cases with a good immune tumor microenvironment of the primary tumor. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12967-018-1692-3) contains supplementary material, which is available to authorized users.