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Background and Importance Triple-negative breast cancer (TNBC) is an aggressive subtype with limited treatment options and poor prognosis. Adding immune checkpoint inhibitors such as pembrolizumab to neoadjuvant chemotherapy has improved pathological response and survival in pivotal trials, becoming a new standard of care. Real-world data are needed to confirm these results in broader patient populations.Aim and Objectives To evaluate the effectiveness of neoadjuvant pembrolizumab plus chemotherapy in patients with early-stage TNBC in a real-world setting and compare outcomes with the pivotal clinical trial (PCT).Material and Methods This retrospective observational study included patients with stage II/III TNBC treated between June-22 and Aug-25. Sex, age, performance status, and stage at diagnosis were collected. The neoadjuvant regimen was pembrolizumab (200 mg/3 weeks, eight cycles) plus chemotherapy: paclitaxel (80 mg/m 2 weekly) and carboplatin (AUC 5 every 3 weeks) for four cycles, followed by doxorubicin (60 mg/m2) and cyclophosphamide (600 mg/m2) every 3 weeks for four cycles. Primary outcome was effectiveness, assessed by pathological response using the Residual Cancer Burden (RCB) classification: pCR (pathological complete response), RCB-I (minimal residual disease), RCB-II (moderate residual disease), and RCB-III (extensive residual disease). Safety was evaluated by treatment-related adverse events (TRAEs).Results Thirty-three women were included, median age 55 years (range 30–78), all with performance status 0. Stage: IIA, n=18 (54.5%); IIB, n=9 (27.3%); IIIA, n=4 (12.1%); IIIB, n=2 (6.1%). Pathological response: pCR, n=16 (48.5%); RCB-I, n=13 (39.4%); RCB-II, n=4 (12.1%); RCB-III, n=0. Most frequent TRAEs: fatigue (87.8%), nausea (60.6%), neutropenia (45.4%), infection (36.3%), diarrhoea (27.2%), anaemia (24.2%), fever (21.2%), dysgeusia (21.2%). In the PCT, pCR rate was 64.8%. Reported TRAEs included nausea (62.7%), alopecia (60.3%), anaemia (55.1%), neutropenia (46.7%), fatigue (41.1%), and diarrhoea (29.4%).In the PCT, efficacy outcomes showed a pCR rate of 64.8% in the pembrolizumab-chemotherapy arm. Reported TRAEs included nausea (62.7%), alopecia (60.3%), anaemia (55.1%), neutropenia (46.7%), fatigue (41.1%), and diarrhoea (29.4%), among others.Conclusion and Relevance In this real-world cohort, neoadjuvant pembrolizumab plus chemotherapy achieved a slightly lower pCR rate than in the PCT, though many patients had minimal residual disease. Safety results were consistent with pivotal data, supporting the clinical value of this regimen in early-stage TNBC.Conflict of Interest No conflict of interest