High baseline tumor-infiltrating lymphocytes (TILs) are associated with a higher likelihood of achieving a pathologic complete response (pCR) in HER2-positive breast cancer regardless of the neoadjuvant chemotherapy regimen, according to a meta-analysis published in Cancer Treatment Reviews.1

High baseline TILs were previously associated with higher pCR rates after neoadjuvant anthracycline- or taxane-based chemotherapy. This analysis evaluated whether patients with high baseline TILs would benefit more from the immune-modulating effects of trastuzumab rather than chemotherapy.

The meta-analysis included data from 5 randomized controlled trials including 1256 women with HER2-positive breast cancer who received neoadjuvant chemotherapy plus trastuzumab and/or lapatinib.

High baseline TILs were associated with a significantly greater pCR rate (odds ratio [OR], 2.46; 95% CI, 1.36-4.43; P = .003), though high heterogeneity was noted (I2 = 74.8%; P = .003), indicating inconsistency across the trials.

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This benefit was observed regardless of the neoadjuvant regimen, with no significant difference between regimens. The OR for pCR was 1.90 with trastuzumab, 1.79 with lapatinib, and 3.06 with the combination. The OR for pCR with an anthracycline plus taxane chemotherapy and anti-HER2 agent(s) was 2.84.

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According to the authors, this study “confirmed the association between high TIL at baseline and increased pCR rates after neoadjuvant treatments with chemotherapy and anti-HER2 agent(s).” They noted that more studies are needed to determine the role of TILs in biopsies and residual disease for guiding treatment decisions.


  1. Solinas C, Ceppi M, Lambertini M, et al. Tumor-infiltrating lymphocytes in patients with HER2-positive breast cancer treated with neoadjuvant chemotherapy plus trastuzumab, lapatinib or their combination: a meta-analysis of randomized controlled trials. Cancer Treat Rev. In press.