Cancer biomarker detection methods

Various methods have been reported for the detection of cancer biomarkers, including PCR, enzyme-linked immunosorbent assay (ELISA), immunofluorescence, chemiluminescent immunoassay (CLIA) and liquid chromatography–tandem mass spectrometry (LC-MS/MS). Zhou et al. [34] developed a sandwich-based ELISA to detect the cancer biomarker carcinoembryonic antigen (CEA) using antibodies immobilized on the plate surface. Several types of cancer that can be associated with elevated CEA levels include colorectal cancer, pancreatic cancer, lung cancer, breast cancer, ovarian cancer, gastric cancer, thyroid cancer and several other cancers. The ELISA method in this study successfully detected the CEA biomarker with good linearity in the range of 2 to 64 ng mL-1 and achieved a limit of detection (LOD) of 2 ng mL-1. However, despite its reliable quantification, the conventional ELISA technique has a LOD only slightly below the nanomolar range, which is insufficient to meet clinical thresholds for many protein biomarkers, particularly in the early stages of disease.

Meanwhile, Park et al. [35] analysed HER2 mRNA expression in Formalin-Fixed Paraffin-Embedded (FFPE) breast cancer tissue samples using the reverse transcription quantitative polymerase chain reaction (RT-qPCR) method. In this approach, HER2 mRNA is first converted into complementary DNA (cDNA) via reverse transcription, followed by amplification with specific primers targeting the HER2 gene sequence. Detection is performed in real-time using fluorescent dyes such as SYBR Green or fluorophore-labelled probes (TaqMan probes), which generate signals proportional to the amount of amplified DNA. The results demonstrated that the RT-qPCR method achieved a sensitivity of approximately 93.0 % and a specificity of about 89.8 %.

Subsequently, Sekacheva et al. [36] reported the clinical validation of a CA-62 biomarker-based CLIA method for early detection of breast cancer. The CLIA method utilizes a light-emitting immunochemical reaction to measure biomarker levels with high sensitivity and specificity. This study demonstrated that the CLIA-CA-62 assay achieved a sensitivity of approximately 92 % and a specificity of 93 %.

Similarly, other advanced analytical methods, such as mass spectrometry-based approaches, also face practical challenges despite their excellent analytical performance. In a study by Chen et al. [37], a quantitative LC-MS/MS method was developed to measure alpha-fetoprotein (AFP) and core-fucosylated AFP in patients with hepatocellular carcinoma (HCC). This method demonstrated excellent performance with a LOD of 15.6 ng mL-1.

Conventional methods such as PCR, CLIA and LC-MS/MS indeed offer high sensitivity and accuracy. However, all three also have practical limitations, including the need for expensive instrumentation and equipment, trained operators, specialized reagents, complex sample-preparation procedures and controlled laboratory environments, which make them less suitable for point of care testing.