Evaluation of the demographic, pathological and clinical characteristics of patients diagnosed with metastatic breast cancer at their initial presentation to the medical oncology clinic

Objective: This study aimed to evaluate the demographic, clinical, pathological, and survival characteristics of 100 patients with de novo metastatic breast cancer (dnMBC) diagnosed at the Department of Medical Oncology, Trakya University Faculty of Medicine. Materials and Methods: A total of 100 female patients diagnosed with dnMBC between 2014 and 2024 were retrospectively analyzed. The diagnosis of metastatic disease was confirmed by imaging methods (CT, PET-CT, etc.), and demographic, clinical, and treatment data were obtained from hospital records. Survival outcomes were assessed using the Kaplan-Meier method and prognostic factors were evaluated with Cox regression analysis. Results: The median age was 54 years and 66% of the patients were postmenopausal. The most frequent molecular subtype was Luminal B (HER2 negative, 30%). Among 64 hormone receptor (HR) positive patients, 59 received endocrine therapy as first-line treatment; 43 were treated with aromatase inhibitors plus CDK4/6 inhibitors and 20 peri/premenopausal patients received LHRH analogs. In cases of endocrine resistance, in the second line treatment 30 patients received fulvestrant and 15 received everolimus. A total of 46 patients received first-line chemotherapy, of whom 44 were treated with taxane-based regimens. All 28 HER2-positive patients received trastuzumab + pertuzumab + taxane; after progression, 16 were treated with T-DM1 and 8 with capecitabine + lapatinib. 4 PD-L1-positive TNBC patients received pembrolizumab. Median OS was not reached, with 1-, 3-, and 5-year OS rates of 86.0%, 70.2%, and 58.6%, respectively. Median PFS was 21.0 months, and TNBC and HER2-positive/HR-negative subtypes showed the worst prognosis. Patients with bone-only metastases had significantly better OS and PFS. In Cox regression, HER2-positive/HR-negative subtype, TNBC, and visceral metastases were independent adverse prognostic factors, whereas HR positivity and low Ki-67 index were associated with better survival. Early treatment response was significant in univariate analysis but was not confirmed as an independent prognostic factor in multivariate analysis, suggesting it may have prognostic value but requires cautious interpretation. Conclusion: dnMBC is a heterogeneous disease. Our findings demonstrate that biological subtype, metastatic pattern, hormone receptor status, proliferation index, and early treatment response play decisive roles in survival and emphasize the importance of personalized treatment approaches. Keywords: De novo metastatic, breast cancer, molecular subtype, survival analysis, prognostic factors.