Abstract P3-11-08: Population characteristics and utilization patterns of patients treated with palbociclib over 2 years of post-approval
Authors: Xu W , Mardekian J , Wang Y , Harnett J , Bell TJ , McRoy L 
Published: February 2018

Background: Palbociclib (PAL) was the first-in-class cyclin dependent kinase (CDK) 4/6 inhibitor approved in the United States (US) in combination with an aromatase inhibitor [AI] or fulvestrant for the treatment of HR+/HER2- advanced/metastatic breast cancer (ABC/MBC) as initial or later-line endocrine therapy (ET). Over 60,000 patients have been treated in the US with PAL since its approval (02/2015). We described population characteristics and utilization patterns in patients who initiated treatment with PAL, using a real-world oncology electronic health record (EHR) database.

Methods: This was a retrospective observational study using de-identified Flatiron (FI) EHR data. As of study cutoff, the FI provider network comprises over 265 community cancer clinics and 3 academic cancer centers across 2500 clinicians and more than 1.5 million active cancer patients throughout the 50 states in the US. Adult MBC patients with a record of initiation with PAL on or after 02/03/2015 (drug approval) and prior to 03/31/2017 (study cutoff) were identified. The line of therapy (LOT) in the metastatic setting was assigned by evaluating systemic treatments (including chemotherapy) pre-and post-PAL initiation. The combination ET was defined as having a record of an ET within 28 days of the recorded order of PAL.

Results: Overall, 1871 patients were identified as having initiated PAL: 1841 (98.4%) are females and 30 (1.6%) are males. Of those females, 1057 (57.4%) received PAL with an AI and 752 (40.8%) received PAL with FUL. Mean follow-up from PAL initiation was 10.2 mos (SD: 6.7) and 36.8% were followed up for &gt;12 mos. Mean age was 64.5 yrs (12.2% ≤50 yrs, 53.1% ≥65 yrs and 21.9% ≥75 yrs). Confirmed HR+/HER2- was observed in 85.1% of patients. Of patients with available ECOG-performance score (PS) at PAL initiation (n=1062), 82.1% had score 0/1, 14.6% had score 2, and 3.3% had score 3/4. Of patients with a known PAL starting dose (n=765), 90.6% initiated at 125mg, 6.7% at 100mg and 2.7% at 75mg. Among patients who initiated PAL with an AI, 45.7% initiated at LOT1, 23.8% at LOT2, 30.6% at LOT3+. Among patients who initiated PAL with FUL, 22.3% initiated at LOT1, 32.5% at LOT2, 45.2% at LOT3+. Among all patients who initiated PAL at LOT1 (regardless of combination partner; n=726), 65.7% used PAL with an AI. A total of 26.3% of patients received chemotherapy before PAL initiation among all females in the metastatic setting, and the most frequent ET regimen following PAL treatment is FUL alone (15.6%).

Conclusions: This study described the palbociclib population and utilization over 2+ years post-approval. Patients who initiated PAL represent the spectrum of those with HR+/HER2- MBC, including both females and males (1.6% of all PAL users). Among female patients, 12.2% were ≤50 yrs of age and 21.9% ≥75 yrs, and 17.9% had ECOG score≥2 at initiation of PAL. Among all females treated with PAL in combination with an AI, more than 45% of patients initiated the regimen at the first line in the metastatic setting. Results with additional follow-up for the same cohort and data on real-world clinical outcomes (provided data become available) will be presented at the conference.

Citation Format: Xu W, Mardekian J, Wang Y, Harnett J, Bell TJ, McRoy L. Population characteristics and utilization patterns of patients treated with palbociclib over 2 years of post-approval [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P3-11-08.