Real-World Treatment Patterns and Clinical Outcomes in Patients Receiving Palbociclib for Hormone Receptor–Positive, Human Epidermal Growth Factor Receptor 2–Negative Advanced or Metastatic Breast Cancer in Argentina: The IRIS Study

PURPOSE: The selective cyclin-dependent kinase 4/6 inhibitor palbociclib was approved in Argentina in 2015 for postmenopausal women with hormone receptor (HR)–positive, human epidermal growth factor receptor 2 (HER2)–negative advanced breast cancer (ABC) or metastatic breast cancer (MBC) based on phase III study results. The Ibrance Real World Insights (IRIS) study aims to evaluate palbociclib in patients with HR-positive/HER2-negative ABC or MBC in the real-world setting in multiple countries globally. Here we report results from patients enrolled in the IRIS study in Argentina. PATIENTS AND METHODS: This retrospective medical chart review study included postmenopausal women with confirmed HR-positive/HER2-negative ABC or MBC who were treated with palbociclib plus letrozole as first-line endocrine-based therapy or with palbociclib plus fulvestrant in women with disease progression after endocrine therapy. Participating physicians reviewed medical records of up to six patients each, collecting demographic and clinical data. Outcomes included progression-free and overall survival rates. RESULTS: Records were extracted for 162 patients in Argentina (palbociclib plus letrozole, n = 105 [65%]; palbociclib plus fulvestrant, n = 57 [35%]). The 6-month progression-free survival rate was 94% for patients treated with palbociclib plus letrozole and 95% for patients treated with palbociclib plus fulvestrant; 85% and 80% of patients treated with palbociclib plus letrozole were progression free at 12 and 18 months, respectively. Six-month survival rates were 98% for palbociclib plus letrozole and 98% for palbociclib plus fulvestrant; 93% and 89% of patients treated with palbociclib plus letrozole were alive at 12 and 18 months, respectively. CONCLUSION: Results from this first real-world evaluation of clinical outcomes in Argentina suggest that palbociclib plus letrozole or fulvestrant delivers favorable effectiveness, as measured by progression-free and overall survival rates.