Survival in ER-positive/HER2-negative non-metastatic invasive breast cancer.

e12631 Background: Non-metastatic invasive breast cancer, estrogen receptor positive (ER+) and human epidermal growth factor receptor 2 negative (HER2-), is one of the most common subtypes, 70-80% of diagnosed cases. It is characterized by a favorable prognosis, with a 5-year survival rate of over 90%. However, there is a high risk of long-term recurrence, so it is crucial to better understand the factors that influence its survival. Methods: Retrospective and observational longitudinal study, using data from medical records of women with breast cancer (2012-2022) at SOLCA Hospital, Guayaquil-Ecuador. Simple random sampling yielded 504 patients. Definitions: Luminal A-like subtype exhibits ER+, PR+ (≥20%), HER2- and Ki-67 <14%; Luminal B-like exhibits ER+, HER2- and at least one of these criteria: Ki-67 ≥14 or PR- or <20%; ER low positive refers to 1-10% expression. Kaplan-Meier estimated overall survival, Log-Rank compared groups, and Cox regression analyzed associated factors. Analyses used SPSS v29, with significance set at p <0.05. Results: Of the 504 medical records reviewed, 156 (HER2+), 100 (ER- or unknown) and 4 (stage IV) were excluded, leaving 244 patients with ER+ and HER2- for analysis. Mean overall survival was 88.3 months (95% CI: 84.1-92.5), with a 5-year survival rate of 80%. According to the Log-Rank method, there was a trend towards longer survival in patients without nodal invasion (p=0.07), progesterone receptor positive (PR+) vs. PR- (p=0.05) and with right vs. left laterality (p=0.14). There were significant differences in survival, being higher in earlier stages (p<0.01), in ER+ vs. ER low positive (p<0.01), in Ki-67 <14 vs. Ki-67 ≥14 (p<0.01) and in Luminal A vs. Luminal B (p=0.04). Survival did not differ significantly across treatment protocols. In Cox regression analysis adjusted for age and those variables, patients with low positive ER showed a 4.8-fold higher risk of death (95% CI: 1.6-14.2) than those with ER+. Conclusions: The 5-year survival rate was lower than in previous studies. Key factors linked to better outcomes include earlier stage, Ki-67 <14 and Luminal A subtype. ER Low positive significantly increases mortality risk, highlighting its prognostic importance. Small sample was a weakness. Baseline characteristics of patients n=244; results in frequency and (%). Age years, mean (s.d.) 56.1 (12.8) Initial Clinical Stage I 27 (11.1) II 133 (54.5) III 61 (25.0) Lymph Nodes Invasion Yes 110 (45.1) No 106 (43.4) Treatment Protocol FAC 30 (12.3) TAC 62 (25.4) AC/T 71 (29.1) Others 47 (19.3) Progesterone receptors Positive 218 (89.3) Negative 26 (10.7) Estrogen receptors Low Positive 12 (4.9) Positive 232 (95.1) Ki-67 < 14 78 (32.0) ≥ 14 165 (67.6) Molecular classification Luminal A 60 (24.6) Luminal B 181 (74.2) s.d.: standard deviation; FAC: 5-Fluorouracil, Adriamycin and Cyclophosphamide; TAC: Docetaxel, Adriamycin and Cyclophosphamide; AC/T: Adriamycin, Cyclophosphamide and Paclitaxel.