432P - Ki67 and progesterone receptor status could be predict sensitivity to cyclin-dependent kinase inhibitor

Background

Cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) combined with endocrine therapy has been approved as first-line treatment for hormone receptor-positive(HR+) advanced breast cancer (ABC). A challenge is finding biomarkers to identify patients who respond to treatment with CDK4/6i.

Methods

We identified all patients in treatment with CDK4/6i for ABC in our centre. Restrospectively, we analyzed the values of Ki 67 and progesterone receptor(PR) detected by inmunohistochemistry and their impact on CDK4/6i duration and progression-free survival(PFS). PFS was evaluated by Kaplan Meier method and survival curves were compared using the longrank test. Results were considered statistically significant with a p value <0’05. Analyses were realized with SPSS.

Results

Between January 2018 and January 2023, 210 patients received CDK4/6i treatment at our institution, 68’6% (144) received palbociclib, 24’3%(51) ribociclib and 7’1%(15) abemaciclib. The media age was 52 years (36-91). The median follow up time was 21 months (range 1-69 months). Ki 67 and PR expression were analyzed both as continuos and dichotomized variables and PR was classified as positive or negative. In the total population, patients with Ki67 >30% had significant shorter CDK4/6i treatment duration versus Ki 67<30% (16’80 months vs not reached, p=0’04). In regard to PR expression, we observed patients with PR positive had longer CDK4/6i treatment duration compared with PR negative (17’54 vs 7’55 months, p=0’027). Also, if we analyzed PFS, we observed patients PR positive had longer PFS versus PR negative (45’50 months vs 17’71 months, p=0’02), we recorded PFS as the duration from the beginning of treatment to disease progression or death, whichever happened first.

Conclusions

In clinical practical, there is a high individual variability in clinical response in patient with CDK4/6i treatment. Actually, there are not biomarkers that predict which patients respond to treatment. In this study, we investigated the impact of Ki67 and PR values on CD4/6i treatment in HR-positive ABC patients. Also, we revealed that PFS seemed to be negatively influenced by elevated Ki 67 values (>30%) and negative PR expression. We have to corroborate these data in prospective studies.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Hospital Universitario Reina Sofia.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.