Real-world Treatment Patterns and Clinical Outcomes Associated With Palbociclib Combination Therapy: A Multinational, Pooled Analysis From the Ibrance Real World Insights Study

Palbociclib was the first cyclin-dependent kinase 4/6 inhibitor approved by the US Food and Drug Administration for use in combination with aromatase inhibitors (AIs) as initial endocrine-based therapy or with fulvestrant in postmenopausal women who previously received endocrine therapy based on data from randomized clinical trials. Real-world studies examining the effectiveness of palbociclib in large, diverse patient populations in routine clinical practice were needed. Ibrance Real World Insights (IRIS) was a retrospective medical record review study of women with confirmed hormone receptor–positive, HER2-negative advanced/metastatic breast cancer treated with palbociclib plus an AI or with palbociclib plus fulvestrant according to approved indications. Participating physicians reviewed medical records of up to 16 sequentially presenting patients, collecting demographic and clinical data. Outcomes included objective response rates, progression-free rates, and survival rates overall and in patients stratified according to age, race and ethnicity, Eastern Cooperative Oncology Group (ECOG) performance status (PS), disease-free interval, visceral disease, liver metastases, bone-only metastases, and previous lines of therapy. Data were abstracted by 417 physicians for 2954 patients in 13 countries; 1415 patients (47.9%) were ≥65 years of age, 369 patients (12.5%) had an ECOG PS ≥2 at initiation, and 835 patients (28.3%) were races other than White. The 12-month progression-free rate was 88% for palbociclib plus an AI and 79% for palbociclib plus fulvestrant; the 12-month survival rate was 96% in both groups. The objective response rates were 80% for palbociclib plus an AI and 75% for palbociclib plus fulvestrant. Palbociclib was similarly effective in most subgroups examined. Data from IRIS provide in-depth, real-world evidence for the use of palbociclib in a range of breast cancer populations in multiple countries. These data support the findings of the randomized PALOMA-2 and PALOMA-3 studies.