Purpose: The present study evaluated whether morphological-measured stromal and intra-tumour tumour-infiltrating lymphocytes (TILs) levels were associated with gene expression profiles, and whether TILs-associated genomic signature (GS) could be used to predict clinical outcomes and response to therapies in several breast cancer subtypes.
Methods: We retrospectively evaluated haematoxylin eosin (HE)-TILs levels and gene expression profiling data from 40 patients with primary breast cancer and extracted the 22 overexpressed genes in cases with high TILs scores as the TILs-GS. The TILs-GS were compared with breast cancer subtype and were evaluated predictive values for prognosis and response to therapies.
Results: Higher TILs-GS expressions were observed for triple-negative and human epidermal growth factor receptor 2 (HER2) positive (+) breast cancers, compared to the luminal types (P < 0.001). With the exception of HER2+, the TILs-GS had no prognostic value in subtypes of breast cancers. The Wilcoxon test revealed significantly different TILs-GS levels between the cases with pathological complete response (pCR) and residual disease after anthracycline and taxane-based neoadjuvant chemotherapy, with the exception of the luminal-low proliferation subtype. In the multivariate analysis, pCR was independently associated with smaller tumour size, higher histological grade, ER negativity, HER2 positivity and higher TILs-GS scores (OR 2.02, 95% CI 1.30-3.14, P = 0.025).
Conclusions: TILs-GS was associated with stromal and intra-tumour TILs levels, as evaluated using HE, which predicted prognosis and chemotherapy response in several breast cancer subtypes. Further studies are needed to perform stratification according to TILs-GS levels and the conventional breast cancer subtypes.
Keywords: Breast cancer; Chemotherapy response; Gene signature; Prognosis; Tumour-infiltrating lymphocytes.