Changes in morphological and immunohistochemical parameters of tumors during neoadjuvant hormone therapy in postmenopausal patients with luminal type of breast cancer.

Objective: Aim: Breast cancer (BC) remains the most common malignant disease among women in Ukraine and worldwide. The indication for neoadjuvant hormone therapy (NAHT) is HR+/HER2- breast cancer of stage II-III. However, there are currently insufficient data on its impact on the IHC biological characteristics of tumors and clinical outcomes.

Patients and methods: Materials and Methods: The study was conducted at the Uzhhorod Treatment and Diagnostic Oncology Center during 2015-2023. At the diagnostic stage, morphological verification and IHC profile were determined based on trephine biopsy material. The study included 28 patients with HR+/HER2- BC, aged from 38 to 75 years old. All patients were prescribed NAHT with the use of aromatase inhibitors for 6.10±2.23 months. The expression levels of ER, PR, Ki-67, category G were assessed before and after NAHT using histological and IHC analyses.

Results: Results: After NAHT, we observed a decrease in Ki-67 levels from 25.31% to 10.25%, ER expression levels from 97% to 84%, and PR expression levels from 87% to 11%. There were changes in category G: G1 was observed in 45.83% of patients, G2 in 54.17%. The staging of BC also decreased. A moderate degree of curative tumor pathomorphosis was achieved in 76.47% of patients, and complete regression (pCR) in 5.88%.

Conclusion: Conclusions: Neoadjuvant hormone therapy demonstrated high efficacy in the treatment of patients with luminal HR+/HER2- BC of stage II-III. In most cases, it was possible to reduce the proliferative activity of the tumor, which was accompanied by a decrease in tumor staging. This made it possible to perform organpreserving surgeries in 60.71%, which confirms the feasibility of using NAHT as an alternative to chemotherapy in certain groups of patients.