CLINICO-MORPHOLOGICAL FEATURES OF THE LUMINAL B SUBTYPE OF BREAST CANCER IN YOUNG WOMEN.

Aim: To evaluate the clinical and morphological features of breast cancer (BC) of the luminal B subtype in young women to determine biological aggressiveness, response to neoadjuvant chemotherapy, and prognosis.

Materials and methods: A retrospective study included luminal B subtype BC patients under 40 years of age (n = 108) and over 55 years (n = 101) treated at the National Cancer Institute. All patients received neoadjuvant chemotherapy according to the ddAC-12T regimen. TNM stages, tumor differentiation grade, Ki-67 expression, hormone receptor status, response to the neoadjuvant chemotherapy (NAC) (RECIST 1.1), pathomorphology grade (Miller - Payne), disease-free (DFS) and overall survival (OS) were analyzed.

Results: Patients of the younger age group were more likely to have G3 tumors (68% vs. 45%), high Ki-67 levels >35% (72% vs. 50%), and lymph node involvement (71% vs. 59%). The median estrogen receptor expression was 35% in the young patients vs. 65% in the older patients. Complete histological response to NAC was achieved in 26% of the young patients (vs. 9% in the older group). Five-year RFS in the young women was 82.4% vs. 94.1% in the older group.

Conclusions: The luminal B subtype of BC in the young women is characterized by the higher proliferative activity, lower hormonal sensitivity, and more frequent lymph node involvement. Despite the response to NAC, this group demonstrates the worse DFS. The results confirm the need for personalized treatment strategies and improved early diagnosis programs in young patients.