Background Comprehensive data from prospective clinical trials have led to a high level of evidence establishing CDK4/6 inhibitors in combination with endocrine treatment (CDK4/6i +
ET) as a standard for the treatment of HER2-negative, hormone receptor-positive (HER2− HR+) breast cancer patients in the first-line advanced therapy setting. Data on patient populations
that have been treated in the real-world setting may provide an insight into changes of patient characteristics and prognosis over time.
Methods The data were extracted from the prospective real-world registry PRAEGNANT (NCT02338167). Patients had to have HER2− HR+ advanced breast cancer in the first-line metastatic
setting. The chosen therapies were described as well as progression-free survival (PFS) and overall survival (OS) in relation to the given therapies and time periods during which they were
indicated.
Results CDK4/6 inhibitors have been rapidly implemented since their introduction in November 2016. In recent years (2018 – 2022), about 70 – 80% of the patient population have been
treated with CDK4/6 inhibitors, while endocrine monotherapy was given to about 10% and chemotherapy to about 15% of all patients. The prognosis was worst in patients treated with
chemotherapy. Recently, mainly patients with a good prognosis are being treated with endocrine monotherapy, and patients who are treated with chemotherapy have an unfavorable prognosis. The
PFS and OS of patients treated with CDK4/6i + ET have remained similar over time despite changes in patient characteristics.
Conclusion A treatment with CDK4/6i + ET has rapidly become the therapy standard for patients in the first-line advanced breast cancer setting. After the implementation of CDK4/6i +
ET, endocrine monotherapy is only given to patients with a very favorable prognosis, while chemotherapy is provided to patients with a rather unfavorable prognosis. These changes in patient
characteristics did not seem to influence the prognosis of patients treated with CDK4/6i + ET.
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