Abstract P4-14-17: Prognostic value of tumor-infiltrating lymphocytes in residual tumors after neoadjuvant chemotherapy concomitant with trastuzumab for HER2-positive breast cancer

Background: Neoadjuvant chemotherapy (NAC) with taxanes, followed by fluorouracil, epirubicin, and cyclophosphamide (FEC), with concurrent trastuzumab is known to achieve a high pCR rate of more than 60% for HER2-positive breast cancer (BC) as well as good prognoses in those obtaining pCR. On the other hand, the prognostic significance of tumor-infiltrating lymphocytes (TILs) has recently been described in triple-negative BC. However, the prognostic and predictive values of TILs in HER2-positive BC remain unclear. In the present study, we examined the grades of TILs in pre-treatment cancer tissues and residual tumors after NAC with trastuzumab, and also investigated its predictive utility for pCR and prognostic power for HER2-positive BC. Patients and Methods: A total of 128 Japanese women with HER2-positive BC received either paclitaxel or docetaxel followed by FEC, with concomitant trastuzumab. The proportional grades of stromal (Str)-TILs in pre-treatment biopsy specimens and residual tumors after NAC with trastuzumab were determined as follows: low grade (0-10%), intermediate grade (10-40%), and high grade (40-90%), using the criteria of the International Working Group for TILs in BC. Analysis 1: The relationship between the grades of Str-TILs in pre-treatment tumors and pCR rates was investigated. Relapse-free survival (RFS) and cancer-specific survival (CSS) were analyzed for a correlation with pre-treatment Str-TILs. Analysis 2: Alterations in the grade of Str-TILs were examined in the residual tumors of non-pCR patients, and RFS and CSS were analyzed for a correlation with residual Str-TILs. Results: pCR was achieved in 83 out of the 128 patients (pCR rate, 64.8%) who received NAC with trastuzumab, and RFS was significantly better in the pCR group than in the non-pCR group (p = 0.0071). Analysis 1: The patient distribution of the Str-TILs grade in pre-treatment tumors was as follows: high: 24 (18.8%); intermediate: 38 (29.7%); and low: 66 (51.6%). pCR rates correlated with the Str-TILs grade in pre-treatment tumors: 83.3% in the high group, 71.1% in the intermediate group, and 54.5% in the low group (p = 0.026); however, the Str-TILs grade in pre-treatment tumors did not correlate with survival. Analysis 2: In 45 non-pCR patients, the distribution of the Str-TILs grade in residual tumors was as follows: high: 9 (20.0%); intermediate: 8 (17.8%); and low: 28 (62.2%), respectively. In non-pCR patients, the rate of a high Str-TILs grade was greater in residual tumors than in pre-treatment tumors (residual, 20.0%, pre-treatment, 8.9%). RFS was significantly better with a high grade than with a low grade of residual Str-TILs (p = 0.033). Conclusions: The status of TILs in pre-treatment tumors predicted responses to NAC concomitant with trastuzumab in HER2-positive BC. The grade of TILs was higher in residual tumors than in pre-treatment tumors, and, among non-pCR patients, the prognosis of patients with a high residual-TILs grade was better prognosis than that of patients with a low residual-TILs grade. We speculate that an examination of TILs in residual tumors after NAC with trastuzumab may be necessary for selecting patients with a good prognosis from non-pCR patients. Citation Format: Kurozumi S, Inoue K, Matsumoto H, Hayashi Y, Tozuka K, Kubo K, Komatsu K, Takai K, Nagai SE, Oba H, Horiguchi J, Takeyoshi I, Kurosumi M. Prognostic value of tumor-infiltrating lymphocytes in residual tumors after neoadjuvant chemotherapy concomitant with trastuzumab for HER2-positive breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-14-17.