The considering both various studies and the EBCTCG meta-analysis, it is reported that the therapeutic effect is correlated with the rate of ER positivity in breast cancer patients receiving endocrine therapy.In this study, it was aimed to evaluate the effect of the percentage of HR positivity on treatment response and prognosis in patients with HR+ HER2- MBC who received CDK 4/6 inhibitor with ET.
In the study, patients who were followed up and treated in Dokuz Eylul University Medical Oncology Department between January 2020-December 2022, diagnosed with HR+ HER-2- MBC and treated with ET (anastrazole, exemestane, fulvestrant, letrozole)+ CDK 4/6 inhibitor (palbociclib and ribociclib) were evaluated retrospectively. Patients with >18 years were included in the study. Appropriate statistical analyzes were used.
The median age at diagnosis of 149 patients included in the study was 55.0 years (26.2-90.2).51.3% (n=77) of the patients were denovo metastatic, and 64% of the patients received CDK 4/6 inhibitor + ET as the first two-line therapy. 18% (n=27) of the patients progressed. 90.7% (n=136) of the patients were still alive. Mean PFS was 26.1 months (95%CI; 22.0-30.2) and mean OS was 34.3 months (95%CI; 31.4-37.2). When we evaluated PFS according to ER positivity rate, the group with ER>50% had numerically longer mean PFS (26.2 months vs. 20.3 months, respectively, p=0.430). Similarly, in the group with ER >50% in OS, the OS was numerically longer, 24.9 versus 34.6 months (p=0.222).When we evaluated the disease control rate (DCR), although it was not statistically significant, DCR was numerically higher in the group with ER>50% as a 81.1% versus 73.7% (p=0.314). While the survival rate was most highest in the group with ER >50%/PR >50% as a 93%, the survival rate was most lowest in the ER 10-49%/ PR negative group as 85.7% (p=0.640).
In conclusion, to the best of our knowledge, this study showed for the first time in the literature that the percentage of hormone receptor positivity has a predictive and prognostic role in HR+ HER-2 MBC patients who were treated with ET with CDK 4/6 inhibitor. The percentage of HR positivity is also important at these patient.
The authors.
Has not received any funding.
All authors have declared no conflicts of interest.