Real clinical practice patterns of palbociclib usage in Russian Federation

Introduction. Current treatment of metastatic luminal Her2-negative breast cancer includes combination of endocrine therapy (ET) with CDK4/6 inhibitors. This type of therapy demonstrated impressive efficacy over mono ET in early lines of treatment in phase III randomized clinical trials. Treatment patterns in real clinical practice (RCP) are of great interest. We represent the first available local data for all CDK 4/6 inhibitors in RCP in Russian Federation in accordance with the number of patients (pts).Aim. Analysis of the patterns of palbociclib administration in RCP.Materials and methods. One hundred and 5 pts from 12 regions of Russian Federation were included in this analysis and received palbociclib in combination with ET from 2017 to 2020. Median age was 57 years (29-75), 31/105 (29.5%) of pts were < 50. De novo metastatic disease was observed in 16 (15.2%) pts, 89 pts progressed after radical treatment. Visceral metastases (mts) at palbociclib initiation had 61/105 (58.1%) of pts.Results. Only 22/105 (21%) of pts received palbociclib as 1st line treatment of metastatic disease. The majority of pts was treated with palbociclib in 2nd and 3rd lines (28.5% and 30.5% respectively). In 26/105 (24.8%) pts palbociclib was combined with aromatase inhibitors, in other cases - with fulvestrant. Median follow-up time was 6.5 (1.1-31.9) months, median progression free survival - 6.0 (1.0-28.0) months. Most common adverse events (AE) were leukopenia, neutropenia and thrombocytopenia. Only in 3 cases palbociclib was completely stopped due to toxicity.Conclusions. Our data indicates that there is a need to move palbociclib initiation in first two lines of treatment to get maximal improvement in survival and to increase its usage in young women.