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Background: Tumor-infiltrating Lymphocytes (TILs) have prognostic value on HER2 positive breast cancer (BC). The absence of standardized method for evaluating TILs causes variations in results of previous studies. This study is performed to evaluate the prognostic value of TILs in HER2 positive BC treated with trastuzumab-based adjuvant therapy using standardized method recommended by the International TILs Working Group.
Aim: To analyze the prognostic value of TILs in HER2 positive BC patients receiving trastuzumab-based adjuvant therapy at Dr. Sardjito General Hospital, Yogyakarta and to analyze proportion differences between high TILs (≥30%) and low TILs (<30%).
Methods: This is a retrospective cohort study on HER2 positive, stage 1-3 BC patients who received trastuzumab-based adjuvant therapy. Histopathology slides from 6 hospitals/laboratories were analyzed by two pathologists.
Results: 73 data were available for analysis. TILs stroma <30% was 65,8% and most patients received combination of anthracyclines, taxanes and trastuzumab (67,1%). There was no difference of overall survival between high and low TILs (p log rank: 0,331).
Conclusion: The proportion of HER2 positive breast cancer with high TILs was lower than those with low TILs. HER2 positive BC with high TILs did not show better overall survival compared to those with low TILs. Our study did not support the theory that different TILs score has prognostic value in HER2 positive breast cancer. Since no formal recommendation for a clinically relevant TIL threshold has been given, further study with bigger samples and better concordance rate among pathologists should be done.
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