Peritumoral FOXP3⁺ regulatory T cell is sensitive to chemotherapy while intratumoral FOXP3⁺ regulatory T cell is prognostic predictor of breast cancer patients.

It has been reported that the prognostic significances of tumor-infiltrating FOXP3(+) regulatory T cells (Tregs) in breast carcinoma depend on their relative density and tissue locations. We here assessed the changes of Tregs before and after neoadjuvant chemotherapy (NC) and their relationships with tumor response and patient survival. Intratumoral and peritumoral infiltration of FOXP3(+) Tregs were evaluated by immunohistochemistry in 132 cases of invasive breast carcinomas before and after NC. After NC, the density of infiltrated Tregs within tumor bed remained stable, whereas it decreased significantly (P = 0.015) in the tissue surrounding tumor. The changes were significant in those tumors that usually response to NC, including the HER2-enriched and basal-like subtypes (P = 0.035; P = 0.004). Univariate and multivariate analyses identified the decreased peritumoral Tregs were an independent predictor for pathologic complete response (pCR), while the intratumoral Tregs after chemotherapy was proved to be associated with overall survival and progression-free survival of the patients. The findings of the study indicated that peritumoral Treg was sensitive to chemotherapy and associated with pCR, while intratumoral Treg was an independent prognostic predictor of breast cancer patients.