OBJECTIVES: CDK4/6 inhibitors (CDKi) ribociclib, palbociclib and abemaciclib were reimbursed in Portugal, specifically to treat pre-and post-menopausal women with HR+/HER2- locally advanced or metastatic breast cancer (a/mBC) in combination with hormonal therapy. The PORTRAIT study characterized CDKi usage and assessed dose adjustments and treatment persistence in a Portuguese a/mBC patients cohort. Given the insights from this study, an additional analysis was developed to estimate the real-world treatment cost with different CDKi.

METHODS: Retrospective longitudinal multicenter study using secondary data from electronic health records of 16 Portuguese public hospitals. Inclusion criteria were defined by the registry of at least one CDKi throughout the patient's treatment history, from January 2018 (first CDKi reimbursement approval in Portugal) to May 2023. Treatment costs were estimated based on package units and dose adjustments reported from treatment start until discontinuation. CDKi packages’ list price was sourced from the official Portuguese database in May 2024. A month was assumed to last 28 days to match CDKi dosage.

RESULTS: Out of 1,926 selected patients, most were post-menopausal women above 50. Median age at CDKi start was comparable between the three drugs and approximately 84% received a CDKi as first-line treatment for a/mBC. The majority of patients were treated with palbociclib (n=992), ribociclib (n=726) and abemaciclib (n=187). Median treatment duration with ribociclib was longer than the remaining CDKi (16 versus 12 months, respectively). Total treatment cost estimates with ribociclib and palbociclib were lower (25.7k€ and 23.6k€) compared to those treated with abemaciclib (27.9k€). Ribociclib’s average monthly cost estimates were 1.6k€ (11% lower than the monthly recommended dose cost), while palbociclib’s and abemaciclib’s cost estimates were 2k€ and 2.3k€, respectively. All three drugs reported similar dose adjustment patterns.

CONCLUSIONS: Ribociclib reported longer treatment duration and lower monthly costs compared to other CDKi. These findings are relevant to the Portuguese public hospitals sustainability.