Abstract 51P
Background
CDK4/6 inhibitor plus endocrine therapy(ET) is the standard treatment of hormone receptor-positive HER2-negative metastatic breast cancer (HR+HER2-MBC). Taxane-based chemotherapy remains a commonly used first line treatment. However, comparative analysis of the two regimens has not been reported in patients that progressed on adjuvant endocrine therapy.
Methods
We identified HR+HER2-MBC patients progressed on adjuvant endocrine therapy, and received taxane-based chemotherapy or CDK4/6 inhibitor plus endocrine therapy as first line treatment.Baseline characteristics and efficacy information was derived from medical record. The primary endpoint was progression-free survival (PFS), the secondary endpoints were objective response rate (ORR), clinical benefit rate (CBR).
Results
Between Oct 1st 2018 and Feb 29th 2024, a total of 263 patients were included, of whom 111 patients received taxane-based chemotherapy, and 152 patients received CDK4/6 inhibitor plus ET as first line treatment. In 111 patients who received taxane-based therapy as initial therapy, 52 patients switched to endocrine therapy as maintenance therapy, the remaining 59 patients continued chemotherapy until disease progression or follow-up time. For the total population, the ORR of taxane-based chemotherapy and CDK4/6 inhibitor plus ET was 35.1% and 19.7%, respectively (P=0.008), while the CBR was 83.8% in the taxane-based chemotherapy arm (including maintenance therapy) and 74.3% in the CDK4/6 inhibitor plus ET arm(p=0.092). There was no statistically significant difference in PFS between patients receiving taxane-based chemotherapy (including maintenance therapy) and CDK4/6 inhibitor plus ET（13.0 vs. 12.0months, p=0.62, HR=1.16 95%CI 0.76-1.77). Subgroup analysis showed that for patients with liver metastasis or PR negative, taxane-based chemotherapy showed superior PFS over CDK4/6 inhibitor plus ET.
Conclusions
For HR+HER2-MBC patients progressed on adjuvant endocrine therapy, first line taxane-based chemotherapy showed higher ORR, similar PFS and CBR, compared with CDK4/6 inhibitor plus endocrine therapy.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The Fifth Medical Centre of Chinese People’s Liberation Army (PLA) General Hospital.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.