Predictive and prognostic value of stromal tumour-infiltrating lymphocytes before and after neoadjuvant therapy in triple negative and HER2-positive breast cancer

Aim: Lymphocyte predominant breast cancer (BC) is associated with higher pathological complete response (pCR) rate after neoadjuvant therapy (NAT) and favorable outcome in triple negative breast cancer (TNBC) and HER2+ BC. The predictive and prognostic impact of stromal tumour-infiltrating lymphocytes (TILs) after NAT and the change of TILs before (pre-) and after (post-) NAT are not well studied. We aimed to assess the predictive and prognostic value of pre- and post-NAT TILs, as well as their pharmacodynamics modulation and their change for TNBC and HER2+ BC. Materials and methods: Two-hundred and nine consecutive patients (n = 80 TNBC, n = 129 HER2+ BC) who received NAT between 2001 and 2009 in a single institution were included. We evaluated the association between pre-NAT TILs and pCR, and the association between pre- and post-NAT TILs, as well as their immunodynamics change with relapse-free survival (RFS) for patients with residual disease (RD). Results: Low pre-NAT TILs compared to int/high were significantly associated with lower pCR rate (TNBC: 4.0% vs 43.6%; HER2+ BC: 26.0% vs 51.9%). The median follow-up period was 98 months. In TNBC with RD, low pre-NAT TILs showed significant association with shorter RFS (HR = 3.844 [1.190–12.421], p = 0.024) in multivariate analysis. Low post-NAT TILs showed borderline significant association with shorter RFS (HR = 2.836 [0.951–8.457], p = 0.061). The change in TILs was not associated with RFS. In HER2+ BC, low pre-NAT TILs were not associated with RFS. Conclusion: In TN and HER2+ BCs, low pre-NAT TILs tumours had a low likelihood of achieving pCR. In TNBC with RD, both low pre- and post-NAT TILs were associated with shorter RFS. These results suggest that TILs information should be taken into account when additional therapies may be given in the post-neoadjuvant setting.