Clinicopathological significance of the immunologic signature (PDL1, FOXP3+ Tregs, TILs) in early stage triple-negative breast cancer treated with neoadjuvant chemotherapy

Patients with breast cancer are appropriate candidates for neoadjuvant chemotherapy (NAC) to facilitate conservative surgery. The chemotherapeutic agents may exert their action by inducing the anti-tumor immune response. This study aimed to evaluate the tumor immune microenvironment including PD-L1, Foxp3+ Tregs, and TILs count in early stages TNBC patients (stage T1, T2) before and after neoadjuvant chemotherapy and their correlation with the clinical and pathological response. Fifty patients of TNBC patients were enrolled in this study; all of them received neoadjuvant chemotherapy. TILs count, Foxp3+ Tregs, and PD-L1 immunohistochemical expression were investigated in all cases before NAC and then evaluated in residual masses after surgery. Data on the clinical and pathological response to NAC were collected and then statistically analyzed. PDL1 expression was detected in 24% of all studied cases, all of them were node-positive (P < 0.002); while Foxp3+ Tregs expressed in 50% and high TILs in 28%. Pathological complete response (pCR) was achieved in 40% of patients and was associated with high TILs expression (P < 0.02) and absence of Foxp3+ Tregs and PDL1 (P < 0.001 for each). In conclusion, Pathologic complete response to NAC was associated with the immunological profile of TNBC. High TILs expression with concomitant decreased PD-L1 expression and low FOXP3+ Tregs is associated with favorable tumor prognosis. Combined therapeutic approaches aiming to PD-L1 block and Tregs depletion might improve treatment efficacy in TNBC.