Tumor-infiltrating lymphocytes (TILs)/volume and prognosis: The value of TILs for survival in HER2 and TN breast cancer patients treated with chemotherapy.

Background And Objective: The use of the tumor microenvironment as a target in creating treatment modalities and as a biomarker in predicting treatment response has become increasingly important. Tumor-infiltrating lymphocytes (TILs), located in the tumor microenvironment, are the fundamental elements of the specific immunological response against tumor cells and have prognostic importance in many types of cancer.

Materials And Methods: Between January 2010 and June 2021, 350 patients who were operated on in our hospital and met the study criteria were included in the study. TILs and tumor-infiltrating lymphocyte volume (TILV) were evaluated in hematoxylin-eosin sections of the patients.

Results: Presence of high stromal TILs was associated with improved survival (p = 0.036), distant metastasis (p = 0.009), high nuclear and histological grade (p < 0.001), estrogen receptor (ER) and progesterone receptor (PR) negativity (p < 0.001), high Ki-67 proliferation index (<0.001), HER2 expression (p = 0.026) level, perineural invasion (p = 0.048), adjuvant chemotherapy (p = 0.005) and radiotherapy (p = 0.055) treatment. High TILV was associated with high nuclear and histological grade (p < 0.001), ER and PR negativity (p < 0.001), HER2 positivity (p = 0.013), high Ki-67 proliferation index (p = 0.001) and high tumor size (p = 0.0011). There was no significant relationship between survival (p = 0.343), distant metastasis (p = 0.632), lymph node metastasis (p = 0.141) and sTIL volume.

Conclusion: TILs are an indicator of an anti-tumor immune response, and tumor suppressor efficiency is increased by chemotherapy and immunotherapy treatments. It is one of the factors that determine the success of the treatment. The tumor-infiltrating lymphocyte is an important parameter that can help determine the patient groups to be treated with chemotherapy, prevent unnecessary complications, and be quickly evaluated in all laboratories without any expense.