OBJECTIVES: CDK 4/6 inhibitors (CDK 4/6i) are indicated for use in combination with aromatase inhibitors or fulvestrant for HR+/HER2- metastatic breast cancer (mBC). The class was first available for use in 2017 with the approval and reimbursement of palbociclib, and later ribociclib and abemaciclib. Equal care across the 21 regions in Sweden is a key element on the Swedish health care agenda. The objective of this study was to investigate the utilization of CDK 4/6i in the 21 Swedish regions.

METHODS: This study utilizes data from the National Pharmaceutical Register where all patients with ≥ 1 filled prescription of a CDK 4/6i from January 2017 – March 2021 were identified and defined as new starters the first available month with filled prescription. The reference population was estimated based on calculations of incident and prevalent patients indicated for treatment with CDK 4/6i (excluding those previously treated). Analysis of utilization was conducted on a national and regional level, by year. Utilization is measured by calculation of patients newly initiating treatment as share of the reference population. Variation in utilization across regions is demonstrated with Min, Max, and quartiles.

RESULTS: The national reference population sum to 2827 patients. 2409 patients who had filled a prescription were identified, 144 with first prescription in 2017 (from April), 619 in 2018, 700 in 2019, 764 in 2020 and 182 in 2021 (through March). National utilization amounts to 8%, 23%, 31%, 40% and 40% for years 2017, 2018, 2019, 2020 and 2021 respectively. Min (Max) over regions vary from 0% to 7% (34% to 106%) between 2017 and 2021 while Q1 vary from 0% to 25%, Median from 9% to 39% and Q3 from 13% to 51%.

CONCLUSIONS: The overall use of CDK 4/6i have increased over time but varies substantially between regions indicating unequal utilization for Swedish HR+/HER2- mBC patients.