Subpopulation structure of tumor-infiltrating lymphocytes in early and locally advanced triple negative breast cancer and its effect on the efficiency of neoadjuvant chemotherapy

Recent studies have shown that triple-negative breast cancer (TN BC) is characterized by the highest mutational load and immunogenicity compared to other subtypes, as well as the degree of tumor-infiltrating lymphocytes (TILs) infiltration, which play an important role in the development of antitumor immunity and treatment response. A significant disadvantage of the standard immunohistochemical method for determining TILs is the inability to fully assess the subpopulation structure of the immune infiltration, including minor populations.
Aim: The evaluation of the subpopulations of breast cancer lymphoid infiltration in patients receiving neoadjuvant chemotherapy (NACT) and its influence on achieving a complete pathomorphological response (pCR = RCB 0).
Materials and methods: The study included 90 patients who received NACT in following regimen: AC (doxorubicin 60 mg/m²  + cyclophosphamide 600 mg/m² ) every 2 weeks, followed by 12 weekly infusions of paclitaxel 80 mg/m²  + carboplatin AUC2. The TILs subpopulations were evaluated in core-biopsy samples prior to the NACT in all patients. The analysis performed by flow cytofluorimetry. Clinical and immunological analysis was performed for the following 9 lymphocyte subpopulations: CD3+CD4+, CD3+CD8+, CD4+CD25^highCD127^{– / low}, CD3–CD19+, CD3–CD16+CD56+, CD3+CD16+CD56+, CD4+CD25+, CD8+CD279+, CD4+CD279+.
Results: The frequency of pCR was 51,1 %. The total TILs content in groups with pCR and non-pCR (RCB 0 vs RCB I–III) did not differ statistically (p = 0.271). The subpopulations analysis for CD3+CD8+, CD3–CD16+CD56+, CD3+CD16+CD56+, CD3+CD4+, CD3–CD19+, CD4+CD25+, CD4+CD25^highCD127^{– / low} and CD4+CD279+ revealed no statistically significant differences between the median values in the groups with pCR and non-pCR. A study of the CD8+CD279+ population showed a higher level of these cells in patients achieved pCR / RCB 0 (median 18,6 % vs 12,3 % with RCB I–III) (p = 0.033). With CD8+CD279+ above the median (high, > Me), the pCR frequency was 61 % vs 35 % in the subgroup with CD8+CD279+ less than or equal to the median (low, ≤Me). Despite the absence of statistically significant differences in the content of CD3+CD16+CD56+(NKT-cells) in groups with pCR and non-pCR (p = 0.091), numerical differences in medians were revealed: 9,9 % and 8,3 %, respectively. At the same time, with CD3+CD16+CD56+(NKT) > Me (high), the pCR frequency was 63 % vs 36 % in the subgroup with CD3+CD16+CD56 + ≤Me (low). When selecting a narrow subgroup (CD8+CD279+ high and CD3+CD16+CD56+ high), the frequency of pCR was 87,5 % vs 27,3 % in the group with both low indicators.
Conclusion: The high content of CD8+CD279+ and CD3+CD16+CD56+ in the tumor sample before the treatment start was a predictor of high sensitivity to NACT and is associated with a higher frequency of pCR.

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