Prediction of Response to Neoadjuvant Chemotherapy in Egyptian Patients with Locally Advanced Breast Cancer: The Evolving Role of Tumour Infiltrating Lymphocytes (TILs)

Background & objectives: Presence of TILs in breast cancer indicates better therapeutic responses to neoadjuvant chemotherapy (NAC), increased pCR and improved outcome. We aim at evaluation of TILs in breast cancer biopsies in correlation with pathological response after NAC in locally advanced breast cancer Methods. This study was conducted at Ain Shams university hospital and Maadi Military hospital in Egypt. 45 Female patients with locally advanced breast cancer were treated with NAC; pathological response was assessed. Tumours were categorized into: luminal A, luminal B, Her2 enriched and TNBC. Assessment of TILs (CD4 and CD8 lymphocytes) was based on Immuno-Oncology Biomarker Working Group guidelines. Results: Tumours were classified into high and low TIL groups using the interquartile range cutoff (29%). High CD4 group showed increased pCR (p = 0.003) and smaller residual tumours (p = 0.04). High CD8 group showed a significant association with smaller residual tumours (p = 0.003). At follow-up of 24-months, CD4 and CD8 high groups showed significantly higher 2-years DFS. The difference between CD4 high and low groups was significant in regards to estrogen receptor status, showing higher levels in hormone-negative tumors (p = 0.029). Patients with Her2 subtype showed higher CD4 (p = 0.007) and CD8 expression (p = 0.018). In CD4 & CD8 low groups, more patients developed local recurrence and distant metastasis (p = 0.025). Conclusion: We concluded that TILs may predict response to NAC and overall prognosis of breast cancer. The evaluation of TILs in correlation with morphological or genomics-based parameters helps to stratify patients of breast cancer.