5PSQ-092 Immunotherapy in neoadjuvant triple-negative breast cancer: effectiveness and safety

<h3>Background and Importance</h3> Pembrolizumab is an anti-PD1 monoclonal antibody that is indicated in combination with chemotherapy as neoadjuvant treatment in triple-negative breast cancer (TNBC). <h3>Aim and Objectives</h3> To evaluate the effectiveness and safety of pembrolizumab in TNBC in a tertiary care hospital. <h3>Material and Methods</h3> Retrospective observational study, in which patients with TNBC who started neoadjuvant treatment from April 2023 to August 2024 were included. The variables collected were: age, sex, quality of life status according to the Eastern Cooperative Oncology Group (ECOG) scale, menopause, tumour size and nodes affected at diagnosis, surgery and number of cycles administered. Effectiveness was determined by the pathological complete response (PCR), evaluated at surgery according to the Miller and Payne scale. Safety was determined by collecting adverse events (AEs) and classifying the degree of toxicity according to the Common Terminology Criteria for Adverse Events v. 5.0 scale. Sources of information: application of electronic prescription and computerised clinical history. The data were analysed with SPSS statistical software v.29. <h3>Results</h3> Thirty-six patients (100% female) were analysed, with a median age of 51.5 years (28–77). All patients presented an ECOG: 0. Fifty percent were premenopausal. Tumour size was: T1 (5.6%), T2 (77.8%), T3 (11.1%), T4 (5.6%) and the affected nodes were: N0 (72.2%), N1 (16.7%), N2 (8.3%) and N3 (2.8%). The median number of cycles received was 6 (1–8). Twenty-two (61.1%) underwent surgery and 14 (38.9%) were still under neoadjuvant treatment. Among these patients who underwent surgery, 86.36% (95% CI, 66.67–95.25) obtained PCR. AEs were recorded in 86.1% of patients. Toxicity grades were: 1–2 (84.8%) and 3 (15.2%). The most frequent AEs were: alopecia (38.8%), nausea (36.1%), neutropenia (22.2%), mucositis (19.4%), skin rash (11.1%), hypertransaminasaemia (9.7%) and neurotoxicity (9.7%). Two patients required hospitalisation for febrile neutropenia and one for immune-mediated hepatitis, both grade 3 AEs. <h3>Conclusion and Relevance</h3> Our PCR results were superior to that demonstrated in the pivotal KEYNOTE 522 trial: 86.36% versus 64.8% respectively. Thus, it is demonstrated that the association of pembrolizumab to neoadjuvant chemotherapy in TNBC is effective to obtain complete response. Regarding the safety profile, toxicity was well-tolerated, except for hypertransaminasemia and neutropenia, which were the most severe. <h3>References and/or Acknowledgements</h3> <h3>Conflict of Interest</h3> No conflict of interest