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In HER2-Negative Metastatic Breast Cancer, Adding CDK4/6 Inhibitor to Endocrine Therapy Helps Survival

Metastatic breast cancer.

 Endocrine therapy plus cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors improved overall survival, progression-free survival, and objective response rate for patients with hormone receptor–positive, HER2-negative metastatic breast cancer, according to results of a meta-analysis published recently in JAMA Oncology. The finding supports continued use of endocrine therapy plus CDK4/6 inhibitor combinations in clinical trials.

The investigators, led by first author Jinming Li, BD, a professor at the Breast Disease Diagnosis and Treatment Center of the Affiliated Hospital of Qinghai University & Affiliated Cancer Hospital of Qinghai University in Xining, China, examined data of 5,043 patients in nine randomized clinical trials found on PubMed, Embase, and databases from the main oncology conference of the European Society of Medical Oncology, the American Society of Clinical Oncology, and the San Antonio Breast Cancer Symposium. The meta-analysis, comprised of one phase 2 trial and eight phase 3 trials, reported on the efficacy and safety of treatment of CDK4/6 inhibitors in combination with endocrine therapy.

Six studies observed overall survival in a total of 3,421 patients, of which  2,030 patients were treated with endocrine therapy plus CDK4/6 inhibitors while the remaining 1,391 patients were treated with endocrine therapy alone. The combination of CDK4/6 inhibitors with endocrine therapy was associated with a statistically significant benefit to overall survival, with a hazard ratio of 1.33.

The trials that analyzed progression-free survival included a total of 3,448 patients who received CDK4/6 inhibitors plus endocrine therapy and 2,267 patients who received endocrine therapy alone. Dr. Li and colleagues found that patients receiving the combination regimen achieved a better progression-free survival outcome, with a hazard ratio of 1.84.

Objective response rate was studied in 3,113 patients who received the combination treatment and in 1,930 patients who received endocrine therapy alone. Objective response rate favored the combination population, with an odds ratio of 2.02. 

Dr. Li and colleagues noted that patients receiving a combination treatment experienced higher rates of adverse events, which included neutropenia, with a hazard ratio of 57.05; leukopenia, with a hazard ratio of 36.36; and diarrhea, with a hazard ratio of 4.97.

"Our meta-analysis showed that, compared with endocrine therapy alone, the use of CDK4/6 inhibitors plus endocrine therapy was associated with significant improvements not only in progression-free survival and overall response rate but also in overall survival among patients with hormone receptor–positive, [HER2]-negative metastatic breast cancer," conclude Dr. Li and colleagues.

In an invited commentary published alongside the study in JAMA Oncology, James Martin, MD, Assistant Professor in Solid Tumor Oncology at Case Western Reserve University School of Medicine, and Lori Goldstein, MD, Deputy Associate Director of Clinical Research at Temple University, stated, "These data support the current clinical practice of discussing the potential benefits of CDK4/6 inhibitors with nearly all patients living with HR-positive, [HER2]-negative metastatic cancer, as recommended by the National Comprehensive Cancer Network guidelines."

For More Information

Li J, Huo X, Zhao F, et al, (2020). Association of cyclin-dependent kinases 4 and 6 inhibitors with survival in patients with hormone receptor–positive metastatic breast cancer: a systematic review and meta-analysis. JAMA Netw Open, 3(10):e2020312. DOI:0.1001/jamanetworkopen.2020.20312 

Martin J & Goldstein L (2020). In support of CDK4/6 inhibitors—a meta-analysis of available randomized data. JAMA Netw Open, 3(10):e2021062. DOI:10.1001/jamanetworkopen.2020.21062

Image Credit: Ed Uthman. Licensed under CC BY 2.0

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