Salvador Bofill, JavierMoreno Anton, FernandoRodriguez Sanchez, Cesar AugustoGalve Calvo, ElenaHernando Melia, CristinaCiruelos Gil, Eva MariaVidal, MariaJiménez-Rodriguez, BegoñaDe la Cruz Merino, LuisMartínez Jañez, NoeliaVillanueva Vazquez, Rafaelde Toro Salas, RubenAnton Torres, AntonioAlvarez Lopez, Isabel ManuelaGavila Gregori, JoaquinQuiroga Garcia, VanesaVicente Rubio, ElenaDe la Haba-Rodriguez, JuanGonzalez-Santiago, SantiagoDiaz Fernandez, NievesBarnadas Molins, AgustiCantos Sanchez de Ibargüen, BlancaDelgado Mingorance, Juan IgnacioBellet Ezquerra, Meritxellde Casa, SoniaGimeno, AsuncionMartin, Miguel2023-05-032023-05-032022-09-24Salvador Bofill J, Moreno Anton F, Rodriguez Sanchez CA, Galve Calvo E, Hernando Melia C, Ciruelos Gil EM, et al. Safety and efficacy of ribociclib plus letrozole in patients with HR+, HER2- advanced breast cancer: Results from the Spanish sub-population of the phase 3b CompLEEment-1 trial. Breast. 2022 Dec;66:77-84http://hdl.handle.net/10668/22065Breast cancer is the most common malignancy and the second leading cause of cancer-related mortality in Spanish women. Ribociclib in combination with endocrine therapy (ET) has shown superiority in prolonging survival in patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) advanced breast cancer (ABC) vs. ET alone. CompLEEment-1 is a single-arm, open-label phase 3b trial evaluating ribociclib plus letrozole in a broad population of patients with HR+, HER2- ABC. The primary endpoints were safety and tolerability. Here we report data for Spanish patients enrolled in CompLEEment-1. A total of 526 patients were evaluated (median follow-up: 26.97 months). Baseline characteristics showed a diverse population with a median age of 54 years. At study entry, 56.5% of patients had visceral metastases and 8.7% had received prior chemotherapy for advanced disease. Rates of all-grade and Grade ≥3 adverse events (AEs) were 99.0% and 76.2%, respectively; 21.3% of patients experienced a serious AE, and 15.8% of AEs led to treatment discontinuation. AEs of special interest of neutropenia, increased alanine aminotransferase, increased aspartate aminotransferase and QTcF prolongation occurred in 77.8%, 14.8%, 11.4% and 4.0% of patients, respectively. Patients aged >70 years experienced increased rates of all-grade and Grade ≥3 neutropenia and anemia. Efficacy results were consistent with the global study. Results from Spanish patients enrolled in CompLEEment-1 are consistent with global data showing efficacy and a manageable safety profile for ribociclib plus letrozole treatment in patients with HR+, HER2- ABC, including populations of interest.enAttribution 4.0 Internationalhttp://creativecommons.org/licenses/by/4.0/Advanced breast cancerCDK4/6 inhibitorPostmenopausalPremenopausalRibociclibÁrea de Gestión Sanitaria de Jerez, Costa Noroeste y Sierra de CádizHumansFemaleMiddle AgedBreast NeoplasmsLetrozoleReceptor, ErbB-2AminopyridinesAromatase InhibitorsProtein Kinase InhibitorsNeutropeniaAntineoplastic Combined Chemotherapy Protocolsresearch article36206609open accessAminopiridinasInhibidores de proteínas quinasasInhibidores de la aromatasaNeoplasias de la mamaProtocolos de quimioterapia combinada antineoplásica10.1016/j.breast.2022.09.0061532-3080PMC9535465http://diposit.ub.edu/dspace/bitstream/2445/190742/1/PIIS0960977622001606.pdfhttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC9535465/pdf