Non-small cell lung cancer (NSCLC) is one of the leading causes of cancer death in the world. Despite the development of various lung cancer treatment methods, including surgery, radiation therapy, endocrine therapy, immunotherapy, and gene therapy, chemotherapy remains the most common approach for treating cancer. The risk of tumors acquiring resistance to chemotherapy remains a significant hurdle to the use of this approach for the successful treatment of various types of cancer. The majority of cancer-related deaths are related to metastasis. Circulating tumor cells (CTCs) are cells that have been detached from the primary tumor or have metastasized and entered the circulation. CTCs can cause metastases in various organs by reaching them through the bloodstream. The CTCs exist in peripheral blood as single cells or as oligoclonal clusters of tumor cells along with platelets and lymphocytes. The detection of CTCs is an important component of liquid biopsy which aids in the diagnosis, treatment, and prognosis of cancer. Here, we describe a method for extracting CTCs from the tumor of patients and using the microfluidic single-cell technique to study the inhibition of multidrug resistance due to drug efflux on a single cancer cell, to propose novel methods that can provide clinicians with more appropriate choices in their diagnostic and treatment approaches.