Use of cyclin-dependent kinase 4 and 6 inhibitors in treating metastatic breast cancer - a year-long experience of Subotica General Hospital in patient follow-up

Abstract

Introduction. According to GLOBOCAN data from 2020, breast cancer ranks first in the number of newly diagnosed malignancies. The treatment of advanced, hormone-positive breast cancer has evolved with the use of cyclin-dependent kinase 4 and 6 inhibitors in first- and second-line treatment for metastatic, hormone-positive, HER2-negative breast cancers, in combination with endocrine therapy. As of May 31, 2022, these drugs have become available in the Republic of Serbia. This paper aims to present a one-year experience of a secondary health center in monitoring patients using the treatments. Material and Methods. The data analysis included patients treated with cyclin-dependent kinase 4 and 6 inhibitors from June 1, 2022, to June 1, 2023, at General Hospital Subotica. The analysis covered demographic data, disease presentation, previous therapies, drug usage, side effects, duration, and therapy outcomes. Patients were categorized into two groups based on age (<60 and >60 years) and by the nature of their disease (relapsed or initially metastatic). Results. A total of 43 patients were treated with cyclin-dependent kinase 4 and 6 inhibitors: 23 (53.5%) in the first line and 20 (46.5%) in the second line. The median therapy duration was eight cycles for patients younger than 60 years. A good therapeutic response was observed in 53.5% of patients. Patients younger than 60 years with late relapse exhibited statistically significantly better treatment outcomes compared to those older than 60 years (p=0.04). The most common site of metastases was the bones (51%, 22 patients), with half of these patients showing a good therapeutic response. Conclusion. Although the observed period is short, ongoing monitoring and further research are planned to share experiences on the use of these drugs.