de la Cruz-Merino, LuisGion, MaríaCruz-Jurado, JosefinaQuiroga, VanesaAndrés, RaquelMoreno, FernandoAlonso-Romero, Jose LRamos, ManuelHolgado, EstherCortés, JavierLópez-Miranda, ElenaHenao-Carrasco, FernandoPalazón-Carrión, NataliaRodríguez, Luz MCeballos, IsaacCasas, MaribelBenito, SaraChiesa, MassimoBezares, SusanaCaballero, RosaliaJiménez-Cortegana, CarlosSánchez-Margalet, VíctorRojo, Federico2025-01-072025-01-072021-10-292072-6694https://hdl.handle.net/10668/24740The PANGEA-Breast trial evaluated a new chemo-immunotherapeutic combination that would synergistically induce long-term clinical benefit in HER2-negative advanced breast cancer patients. Treatment consisted of 21-day cycles of 200 mg of pembrolizumab (day 1) plus gemcitabine (days 1 and 8). The primary objective was the objective response rate (ORR). The tumor infiltrating lymphocytes (TILs) density and PD-L1 expression in tumor, and the myeloid-derived suppressor cells (MDSCs) level in peripheral blood, were analyzed to explore associations with treatment efficacy. Considering a two-stage Simon's design, the study recruitment was stopped after its first stage as statistical assumptions were not met. A subset of 21 triple-negative breast cancer (TNBC) patients was enrolled. Their median age was 49 years; 15 patients had visceral involvement, and 16 had ≤3 metastatic locations. Treatment discontinuation due to progressive disease (PD) was reported in 16 patients. ORR was 15% (95% CI 3.2-37.9). Four patients were on treatment >6 months before PD. Grade ≥3 treatment-related adverse events were observed in 8 patients, where neutropenia was the most common. No association was found between TILs density, PD-L1 expression or MDSCs levels and treatment efficacy. ORR in TNBC patients also did not meet the assumptions, but 20% were on treatment >6 months.enAttribution 4.0 Internationalhttp://creativecommons.org/licenses/by/4.0/MDSCsPD-L1TILsbiomarkersbreast cancerimmunotherapypembrolizumabphase IItriple-negativeresearch article34771596open access10.3390/cancers13215432PMC8582406https://www.mdpi.com/2072-6694/13/21/5432/pdf?version=1635504667https://pmc.ncbi.nlm.nih.gov/articles/PMC8582406/pdf