Increased Stromal Infiltrating Lymphocytes are Associated with Circulating Tumor Cells and Metastatic Relapse in Breast Cancer Patients After Neoadjuvant Chemotherapy

BACKGROUND: Circulating tumor cells (CTCs) intravasate into the bloodstream throughout early cancer stages, promoting metastasis. The tumor microenvironment plays a crucial role in disease progression and outcome. The aim of this prospective study was to investigate the associations of intratumoral and stromal tumor-infiltrating lymphocytes (TILs) with CTCs among patients receiving neoadjuvant chemotherapy (NAC). METHODS: We analyzed CTCs in 30 patients with primary breast cancer before and after NAC. The numbers of intratumoral TILs (iTILs) and stromal TILs (sTILs) from pre-NAC formalin-fixed paraffin-embedded core biopsies and post-NAC surgical samples were analyzed. The associations of TILs with pathologic complete response (pCR) and outcome were also evaluated. RESULTS: Of the 30 patients, pCR was achieved in nine (30.0%) patients. A total of 25 (83.3%) patients were CTC-positive before NAC, and eight (26.7%) patients were CTC-positive after NAC. Neither CTC detection before NAC nor CTC after NAC was predictive of pCR. Nevertheless, the presence of CTCs after NAC was significantly associated with early metastatic relapse (P = 0.049) and worse disease-free survival (P = 0.009). After NAC, total sTILs, CD4(+) T cells, and CD8(+) T cells were significantly correlated with CTC detection. Increased infiltration of sTILs and CD4(+) T cells was also an unfavorable prognostic factor as measured by the rate of metastatic relapse. CONCLUSION: Detection of CTCs after NAC was positively associated with the metastatic relapse of breast cancer patients. Increased infiltration of sTILs after NAC was correlated with CTCs and was found to be an unfavorable prognostic factor.