Predictive value of progesterone receptor in advanced-stage breast cancer patients treated with CDK4/6 inhibitors

İrem Öner; Bediz Kurt İnci; Pınar Kubilay Tolunay; Berkan Karabuğa; Alper Türkel; Öztürk Ateş; Cengiz Karaçin

doi:10.38053/acmj.1670333

Predictive value of progesterone receptor in advanced-stage breast cancer patients treated with CDK4/6 inhibitors

Authors : İrem Öner, Bediz Kurt İnci, Pınar Kubilay Tolunay, Berkan Karabuğa, Alper Türkel, Öztürk Ateş, Cengiz Karaçin

Pages : 375-383

Doi:10.38053/acmj.1670333

View : 72 | Download : 102

Publication Date : 2025-05-30

Article Type : Research Paper

Abstract :Aims: Phase III studies investigating CDK 4/6 inhibitors have failed to identify significant predictive or prognostic markers that aid clinicians in therapeutic decision-making. Given the complex treatment landscape in breast cancer, identifying patient and tumor characteristics that optimize the utilization of CDK 4/6 inhibitors across diverse therapeutic approaches is crucial. In our study, we aimed to evaluate the predictive role of progesterone receptor (PR) expression levels in patients with estrogen receptor (ER)-positive and human epidermal growth factor receptor 2 (HER2)-negative advanced-stage breast cancer treated with CDK 4/6 inhibitors. Methods: This study retrospectively evaluated 244 patients who received a combination of CDK 4/6 inhibitors and endocrine therapy as their first-line treatment. Those with PR levels below 20% were designated as low PR expression patients, and those with levels of 20% or above were classified as high PR expression patients. These two groups were compared in terms of demographic characteristics and progression-free survival (PFS). Results: Progression events occurred in 37 of 83 patients in the low PR expression group and 55 of 161 patients in the high PR expression group. Patients with low PR expression demonstrated a significantly shorter median PFS of 23.13 months (95% CI, 15.67-30.59) compared to those with high PR expression, who exhibited a median PFS of 34.66 months (95% CI, 24.2745.05) (p=0.002). This significant difference in mPFS was observed consistently across both ribociclib (p=0.034) and palbociclib (p=0.024) treatment groups. Conclusion: This study suggests that PR expression may also predict disease progression in patients initiating CDK 4/6 inhibitors and endocrine therapy in addition to ER levels. While these findings are promising, further research is warranted to validate them in more extensive, prospective studies.
Keywords : Advanced stage breast cancer, biomarker, CDK 4/6 inhibitors, endocrine therapy, progesterone receptor

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