Clinical outcomes in patients receiving palbociclib + fulvestrant as first line treatment for ABC/MBC in real world settings in the United States.

e13041 Background: Palbociclib in combination with fulvestrant is approved in women with HR+/HER2- advanced/ metastatic breast cancer (ABC/ MBC) with disease progression following prior endocrine therapy. In this analysis we seek to assess the real world effectiveness of palbociclib + fulvestrant in women who had failed endocrine therapy in adjuvant settings and had received Palbociclib + fulvestrant as first line treatment for ABC/ MBC. Methods: Medical records of adult female patients in the US with HR+/HER2- ABC/MBC who received palbociclib + fulvestrant were reviewed by their treating physicians as part of the Ibrance Real World Insights (IRIS) study. Data on demographic and clinical characteristics, treatment patterns, and clinical outcomes were abstracted. Progression free rate and survival at 6 and 12 months were estimated via Kaplan-Meier analysis. Results: Medical records of 652 patients receiving palbociclib were abstracted by 65 physicians, of which 63.1% were from community settings. Of the 292 patients who received palbociclib + fulvestrant, 106 patients (36.3%) received it as first line treatment for ABC/ MBC. The mean (SD) age of patients at palbociclib initiation was 60.8 (13.2) years (median, 62.0 years) and ECOG performance status was mostly 0 (37.7%) or 1 (42.5%). Visceral disease was seen in 40.8% of patients and 78.9% of patients had bone metastases. The median duration between initial breast cancer diagnosis and ABC/ MBC diagnosis was 42.9 months. Most patients (77.4%) started at an initial dose of 125 mg/ day, while 12.3% and 10.4% started at 100 mg/ day and 75 mg/ day respectively. Dose reductions were seen in 14 patients (13.2%). Based on physician assessment, the majority of patients (75.9%) had partial response or stable disease. The 6 and 12 month progression free rates were 97.1% and 89.6% respectively. The survival rates at 6 and 12 months were 100% and 91.1% respectively. Conclusions: Rate of dose reductions for palbociclib in clinical practice was found to be low. Palbociclib + fulvestrant appears to be effective and well tolerated in first line ABC/ MBC settings in women who have previously failed endocrine therapy. Funding: Pfizer, Inc