Objective  To analyze the predictive value of tumor-infiltrating lymphocyte (TIL) fraction in patients with breast cancer treated with neoadjuvant chemotherapy.

  Methods   Clinicopathological data of 156 female patients with breast cancer diagnosed using core needle biopsy and treated with neoadjuvant chemotherapy and surgery between November 2015 and April 2017 in Tianjin Medical Uninvertity Cancer Institute and Hospital were retrospectively analyzed. Patients were assigned into 3 groups based on the TIL fractim, namely high, intermediate and low TIL fractin gronp. The response to neoadjuvant chemotherapy was evaluated using the histopathological criteria for assessment of therapeutic response in breast cancer. The relation between TIL fraction and response to neoadjuvant chemotherapy was then analyzed.

  Results   Neoadjuvant chemotherapy was effective in 78.2% (122/156) of the patients. Patients harboring tumors with a higher TIL fraction were more likely to achieve a better response to neoadjuvant chemotherapy than those harboring tumors with a lower TIL fraction (P < 0.01). Patients harboring hormonal receptor (HR)-negative tumors generally exhibited a higher TIL fraction than those harboring HR-positive tumors (P < 0.01). The TIL fraction, but not HR status, human epidermal growth factor receptor 2 (HER-2) status, or Ki-67 index, correlated with response to neoadjuvant chemotherapy.

  Conclusion  TIL fraction is an independent predictive factor of response to neoadjuvant chemotherapy in patients with breast cancer. Patients with breast cancer exhibiting higher TIL fraction achieve better response to neoadjuvant chemotherapy than those exhibiting lower TIL fraction.