Аннотация:Background: Breast cancer (BC) is the most common cancer in women worldwide. The purpose of the study was to analyze immediate and long-term results of treatment in patients with locally advanced primarily inoperable HER2-negative breast cancer depending on the time of progression. Methods: The study included 104 women with locally advanced primarily inoperable HER2-negative breast cancer who developed an early disease progression within 6 to 12 months after standard combination treatment. The blood levels of circulating tumor cells (CTCs) were measured in all patients during the progression stage. Results: An analysis of the overall (OS) and event-free (EFS) survival showed that median EFS in patients with luminal B subtype was 9 months, in patients with triple-negative (TNBC) subtype 8 months. EFS at 6 months was 87.5% in luminal B subtype and 79.4% in TNBC, p = 0.37985. Median OS in patients with luminal B subtype was 25 months, in patients with TNBC 26 months. One-year OS was 100% in luminal B subtype and 93.9% in TNBC, p = 0.138. 2-year OS was 54.2% in luminal B subtype and 55.9% in TNBC, p = 0.697. 3-year OS was 37.5% in luminal B subtype and 41.2% in TNBC, p = 0.639. CTCs were detected in all patients, with higher levels in patients with luminal B subtype than in TNBC patients. HER+ CTCs were found in 30% of patients with luminal B subtype but not registered in patients with TNBC. Such results were obtained for the first time. Conclusions: The absence of significant differences demonstrated the aggressive disease course in patients with luminal BC with identified primary hormone resistance, similar to the TNBC course. The results should be taken into account when predicting the course of the disease and developing further treatment tactics.