REAL WORLD EVIDENCE ON THE EFFECTIVENESS OF RIBOCICLIB PLUS AROMATASE INHIBITORS AS FIRST-LINE TREATMENT OF BRAZILIAN PATIENTS WITH HORMONE RECEPTOR-POSITIVE/ HER2-NEGATIVE ADVANCED BREAST CANCER (HR+/HER2–ABC): THE BRASILEEIRA STUDY

Cyclin-dependent kinase (CDK) 4/6 inhibitors are the recommended standard of care for the treatment of HR+/HER2-ABC. Ribociclib (Kisqali®) is the only CDK demonstrating clinically and statistically significant overall survival benefit across all three phase 3 MONALEESA trials. As data on effectiveness are scarce and Latin American populations are underrepresented in randomized trials, this study evaluated the effectiveness and safety of ribociclib in a national cohort of Brazilian patients. The study was longitudinal, retrospective, and multicenter, including patients ≥ 18 years of age with HR+/HER2-ABC who had at least 1 year of follow-up after treatment initiation. Data were collected from medical records with an electronic case report form following both Good Clinical and Pharmacoepidemiology Practices. The study was approved by all institutions’ ethics committees. The primary outcome was progression free survival at 12 months. Secondary outcomes included disease progression at 6 and 12 months, death at 6 and 12 months, dose reduction or discontinuation, and safety. All analyses were performed in R software by an independent third-party Academic Research Organization. A total of 76 patients were included by 11 Brazilian institutions. Mean age was 57 years, 28.9% were Black/Brown, and 34.2% had stage IV at diagnosis. About 26.0% were endocrine-resistant and 54.1% had more than 3 metastatic sites. At 12 months, 77.6% (95% confidence interval: 66.3%-86.1%) were alive and progression-free. There were 16 events of disease progression and 3 deaths (patient-year event rate of 20.8 and 3.9, respectively). Dose reduction occurred in 37.7% of patients, and 3 patients discontinued treatment due to adverse events. Side effects were consistent with published literature. The results of the BrasiLEEira study in the real-world setting are consistent with evidence from pivotal MONALEESA trials with ribociclib. This is the first report of ribociclib results in an underrepresented population, and further analyses are planned.