Comparison of Tumor Microenvironments Between Primary Tumors and Brain Metastases in Patients With NSCLC

INTRODUCTION: This study investigates the immune profile of the primary lung tumors and the corresponding brain metastasis from patients with NSCLC using multiplex fluorescence immunohistochemistry. METHODS: The study evaluated 34 patients who underwent autopsy or surgical resection for brain metastasis and autopsy, surgical resection, or core biopsy for primary lung cancer. We compared the densities of various immune cells in the primary tumors and the brain metastases by multiplex fluorescence immunohistochemical analysis. RESULTS: The density of CD4-positive (CD4(+)) T-cells, CD8-positive T-cells, and CD4(+) Foxp3-positive T-cells were statistically higher in both tumor and stromal areas in primary lung cancer specimens when compared with brain metastases samples (p < 0.0001). Only CD204-positive cells were statistically higher in the tumor areas of the brain metastases (p = 0.0118). Tumor-infiltrating lymphocytes associated with brain metastases positively correlated with overall survival, but primary lung tumor-infiltrating lymphocytes did not. The density of CD4(+) and CD4(+) Foxp3-positive T-cells in brain metastases with radiation was statistically higher in the carcinoma and stromal areas compared with those without radiation (p = 0.0343, p = 0.0173). CONCLUSIONS: Our findings that CD204-positive cells were higher in brain metastases may have broader implications for treatment as these macrophages may be immunosuppressive and make the immune environment less reactive. Furthermore, the finding that the density of CD4(+) T-cells was higher in cancer and stroma areas of brain metastases after radiotherapy supports the addition of immunotherapy to radiation therapy in the treatment of brain metastases in NSCLC.