The presence of stromal tumor-infiltrating lymphocytes (STILs) is associated with recurrence-free survival (RFS) in women with human epidermal growth factor receptor 2 (HER2)-positive breast cancer treated with chemotherapy alone; however, this association was not seen in women treated with chemotherapy plus trastuzumab. These study findings were published online first in JAMA Oncology.

The presence of tumor-infiltrating lymphocytes is a prognostic factor in patients with triple-negative breast cancer. 

In this study, the researchers sought to determine the association between presence of STILs and RFS in women with early stage HER2-positive breast cancer who received chemotherapy alone or chemotherapy plus trastuzumab. The women included in this study were clinical trial participants assigned to 2 of the 3 arms of the N9831 trial.

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Using Cox models, the researchers assessed hematoxylin eosin-stained tumor slides from N9831 trial participants who received doxorubicin-cyclophosphamide followed by weekly paclitaxel (489 patients in arm A [standard chemotherapy]) or doxorubicin-cyclophosphamide followed by weekly paclitaxel plus trastuzumab followed by trastuzumab alone (456 patients in arm C [chemotherapy plus trastuzumab]). Assessment for STILs was done at an academic medical center. Mean follow-up was 4.4 years.

The 10-year Kaplan-Meier estimates for RFS in the patients from arm A were 90.9% for those with high levels of STILs and 64.5% for those with low levels of STILs. RFS estimates for the patients from arm C were 80.0% for those with high levels of STILs and 80.1% for those with low levels of STILs.

Interaction between trastuzumab treatment and STIL status was statistically significant, and remained significantly associated with RFS in arm A but not in arm C on multivariable analysis.

Furthermore, these results are in contrast to previous reports of an association between high levels of STILs and increased benefit of trastuzumab treatment in patients with HER2-positive breast cancer.


1. Perez EA, Ballman KV, Tenner KS, et al. Association of stromal tumor-infiltrating lymphocytes with recurrence-free survival in the N9831 adjuvant trial in patients with early-stage HER2-positive breast cancer [published online ahead of print October 15, 2015]. AMA Oncol. doi:10.1001/jamaoncol.2015.3239.