<![CDATA[Background: Triple-negative breast cancer (TNBC) is a uniquely aggressive molecular subtype associated with poor prognosis, high proliferation rates, and significant genomic instability. Objective: This study aimed to determine the clinicopathologic characteristics, pathological response, and safety profile of TNBC patients in a local clinical setting. Method: A retrospective cohort study was conducted on 50 female patients at a private hospital in Yogyakarta (2019–2022). Chemotherapy regimens were categorized into platinum-based (carboplatin and taxane) and non-platinum-based (anthracycline-taxane, capecitabine, or methotrexate) groups. Pathological complete response (pCR) was defined as the total absence of residual invasive carcinoma in both the breast tissue and sampled regional lymph nodes (ypT0/Tis ypN0). Data were extracted from medical records and analyzed using bivariate statistical tests. Results: The mean age was 48.48 years (95% CI: 46.24–50.72), with 76% of patients aged 40-59. Most patients presented with cT2 tumor size (38%) and cN0 nodal status (58%). The mean Ki67 index was 24.96 (95% CI: 19.29–30.63), with 44% of patients exhibiting high proliferation (? 30%). The overall pCR rate was 20% (10/50). The platinum group achieved a higher numerical pCR rate (25%, 6/24) compared to the non-platinum group (15.4%, 4/26), though the difference was not statistically significant (OR = 1.833, 95% CI: 0.448–7.511, p = 0.490). A high Ki67 index (? 30%) was significantly associated with superior pCR achievement (OR = 7.428, 95% CI: 1.365–40.413, p = 0.014). Adverse drug reactions (ADRs) occurred in 66% (33/50) of patients, predominantly chemotherapy-induced nausea and vomiting (22%) and neurological disorders (20%). Conclusion: High Ki67 expression was associated with therapeutic response in this cohort. No statistically significant difference in pCR or total ADR incidence was observed between regimens in this sample. The study is limited by its single-center design and small sample size (n=50)]]>
