The Effectiveness of Neoadjuvant Therapy in the Treatment of Patients with Locally Advanced Breast Cancer

Aim: to assess the severity of the pathomorphological response according to the classification of Residual Cancer Burden (RCB) in patients with breast malignancies depending on the surrogate molecular biological subtype after neoadjuvant drug therapy (chemotherapy ± anti- HER2 therapy). Design: Retrospective comparative study. Materials and methods. The retrospective study included 90 patients with breast cancer (T0-3, N0-1, M0) with luminal In HER2-negative, luminal In HER2-positive, HER2-positive non-luminal, thrice negative subtypes who were on complex treatment. The age of women ranged from 26 to 39 years (median age — 36 years). A retrospective analysis of the evaluation of residual tumor load in 85 patients according to the RGB system after neoadjuvant drug therapy and subsequent surgical treatment was performed. Results. In patients with luminal B HER2-negative breast cancer, a complete pathomorphological response was noted in 20% of cases, in 16% — RCB-I, in 36% — RCB-II, in 28% — RCB-III. Among women with luminal B HER2-positive breast cancer, a complete response was achieved in 26.67%, RCB-I was noted in 33.33%, RCB-II — in 13.33%, and RCB-III — in 26.67%. Among the patients with HER2-positive breast cancer, 46.16% had RCB-0, 23,08% had RCB-I, 15.38% each had RCB-II and RCB-III. In participants with thrice negative breast cancer, a complete response was achieved in 41.94% of cases, RCB-I was noted in 22.58%, RCB-II — in 19.35% and RCB-III — in 16.13%. The frequency of complete pathomorphological response (RCB-0) after neoadjuvant chemotherapy significantly differed among the more aggressive subtypes of breast cancer (thrice negative and HER2-positive), compared with HER2-negative (p < 0.0001). Conclusion. The unified assessment of the residual tumor after neoadjuvant therapy makes it possible to clearly identify prognostic groups of patients with different treatment responses and plan additional drug therapy for them. Keywords: neoadjuvant chemotherapy, targeted therapy, breast cancer, HER2.