Tehran University of Medical Sciences Basic & Clinical Cancer Research 2228-6527 15 4 2024 10 12 225 236 Saba Mirzaei Department of Medical Genetics, Institute of Medical Biotechnology, National Institute of Genetic Engineering and Biotechnology (NIGEB), Tehran, Iran Mahdieh Salimi National Institute of Genetic Engineering and Biotechnology (NIGEB) Hossein Mozdarani Department of Medical Genetics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran 2024 06 28 2024 08 10 Background: Breast cancer is the leading cause of death for women worldwide. Optimal methods for most cancer control require the use of appropriate biomarkers. Recently, circular RNAs (circRNAs), as closed-loop RNA molecules generated through reverse splicing, have emerged as promising biomarkers for cancer development.  Methods: In this observation, the expression of 3 unique circRNAs - cdr1as, circRNA-000284, circ-ITCH - within the peripheral blood of breast cancer patients was studied using Real-Time RT-PCR before and after chemotherapy compared with the control.   Results: The data confirmed that the analyzed circRNAs expression was significantly altered in breast cancer patients compared to the controls. These alterations have been related to advanced stages, lymph node involvement, and metastasis. CircRNA-000284 expression considerably decreased after chemotherapy. This may proposed its potential as a biomarker for monitoring treatment response. Conclusion: These findings provide valuable insights for the development of novel  strategies in the management and treatment of breast cancer. However, further studies are required to validate the clinical utility of these circRNAs as biomarkers and to explore their underlying mechanisms in breast cancer progression. https://bccr.tums.ac.ir/index.php/bccrj/article/view/544