Predictive value of tumor-infiltrating lymphocytes for response to neoadjuvant chemotherapy and breast cancer prognosis.

BACKGROUND Tumor-infiltrating lymphocytes (TILs) are predictive for the response to neoadjuvant chemotherapy (NAC) of breast cancer. However, little is known about the predictive value of TILs for axillary lymph node involvement after NAC. METHODS We analyzed 282 breast cancer patients who were operated following NAC and curative surgery from 2008 to 2018. TILs were assessed in core needle biopsies before NAC, and the biopsies were divided into three groups: low (0%-10% immune cells in stromal tissue within the tumor), intermediate (11%-59%), and high (≥60%). The patients were followed for an average of 63 months (range, 2-116 months). We analyzed retrospectively the predictive value of TILs for the response to NAC, including pathological complete response (pCR) and axillary lymph node involvement (positive lymph node ratio (LNR; the ratio of the number of nodes involved to the total number of nodes dissected)). The prognostic values of TILs and LNR were assessed. RESULTS A pCR was achieved in 27 of 188 patients (14.4%) in the low-TIL group, in 14 of 57 patients (24.6%) in the intermediate-TIL group, and in 13 of 37 (35.1%) in the high-TIL group (p = .007). Among patients who underwent axillary lymph node dissection after NAC, patients with high TILs had lower LNR (p = 0021) compared with the other groups. Kaplan-Meier analysis showed that overall survival (OS; p < .001) and disease-free survival (p < .001) were significantly longer for patients with low LNR (≤0.2). TILs were positively correlated with disease-free survival (p = .028), but TILs did not correlate with OS (p = .171). Moreover, by multivariable analysis, LNR independently affected disease-free survival (p < .001). CONCLUSIONS TILs may be predictive for pCR rate, postoperative residual lymph node involvement, and disease-free survival of breast cancer patients. High TILs may suggest favorable outcomes.