The presence of stromal tumor-infiltrating lymphocytes (STILs) was prognostically associated with recurrence-free survival (RFS) in patients treated with chemotherapy alone but not in patients treated with chemotherapy plus trastuzumab. This according to a study of 945 women with early-stage HER2-positive breast cancer treated with chemotherapy or chemotherapy plus trastuzumab. Researchers found:

• 10-year Kaplan-Meier estimates for RFS in patients treated with chemotherapy alone were 90.9% and 64.5% for patients with high and low levels of STILs, respectively.

• 10-year Kaplan-Meier estimates for RFS in patients treated with chemotherapy plus trastuzumab were 80.0% and 80.1% for patients with high and low levels of STILs, respectively.

• Interaction between trastuzumab and STIL status was statistically significant.

• In multivariable analysis, STIL status remained statistically significant in patients treated with chemotherapy alone, but not in patients treated with chemotherapy plus trastuzumab.

Citation: 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]. JAMA Oncol. doi: 10.1001/jamaoncol.2015.3239.