Patients with HR+/HER2- metastatic breast cancer treated with CDK4/6 inhibitors: a real-world study in Italy

Aim: Italian real-world analysis of CDK4/6 inhibitor (CDK4/6i) treatment in HR+/HER2- metastatic breast cancer aimed at evaluating patients' medical history, treatment duration, treatment patterns (combination with endocrine therapy), line of therapy and drug dose variations. Materials & methods: CDK4/6i treatment was analyzed using healthcare administrative databases covering 18% of Italians between January 2017 and June 2022. Results: Among CDK4/6i-treated women, palbociclib and abemaciclib (were more frequently combined with fulvestrant, while ribociclib with aromatase inhibitors. CDK4/6i recommended doses were initiated in 72–90% patients and maintained after 3–6 months in respectively 65–57% women. Frontline CDK4/6i use grew over time (reaching 90%). Median time-to-treatment discontinuation was 11.0 months in palbociclib, 15.9 in abemaciclib and 15.4 in ribociclib cohorts. Conclusion: CDK4/6i plus endocrine therapy is increasingly utilized as first-line therapy, with low proportions of dose reductions within 6 months and discontinuations at 1 year.