Biomarkers are specific biological mechanisms and entities that may exist in many forms and may indicate the existence of cancer in the body through their presence or activity. These processes and substances can be detected to identify the presence, risk of, and progression of cancer, as well as its response to medication.
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Current research is uncovering new biomarkers for specific cancers with different clinical applications. We discuss what these biomarkers are, how they are identified, and how they are used in the treatment, diagnosis, and prevention of cancer.
What is a biomarker of cancer?
Cancerous cells can contain or produce substances that can be detected by certain techniques. In addition, other bodily cells have been found to produce substances in the presence of neighboring cancerous cells. The substances produced by healthy cells in response to the existence of cancerous cells can also be detected to signify the presence of cancer.
These substances can provide information on key factors that enable doctors to make informed decisions about treatment plans that are tailored to the person. They can give information on how aggressive the cancer is and indicate whether it can be treated with targeted therapy, as well as revealing how well a current treatment method is working.
The diagnosis, prognosis aspects, and epidemiology of cancer are already benefiting from the numerous types of biomarkers that have been identified. Genetic, epigenetic, glycomic, proteomic, and imaging biomarkers are all kinds of biomarkers that are being used in cancer research and treatment.
In a clinical setting, a large number and variety of biomarkers are being used to detect cancer. Within this set of biomarkers, some are linked with just one type of cancer, and others are more general. However, at this point, there has been no comprehensive biomarker found that is able to indicate the presence of any and all cancers.
Identifying biomarkers
Most traditional markers of tumors are proteins that are not specific to cancerous cells, but those that appear in higher volumes in cancerous tissue. Assays can be used to measure the quantity of the substance, typically via non-invasive methods such as the collection of biofluids including blood or serum, urine, or stool, though direct biopsies of tumors and or tissues can also be taken to be studied.
Recently, the protocol of using biomarkers has seen a shift. Genetic markers are being used with an increasing frequency. A growing body of research is deepening the knowledge surrounding the role of genetic involvement in different kinds of cancer. Tumor gene mutations, patterns of expression of tumor genes, and alterations in tumor DNA are all currently being used effectively as biomarkers of tumors.
Clinical uses of cancer biomarkers
Biomarkers play vital roles at different stages of the disease. They have been developed for various uses in oncology, such as in screening, diagnosis, prognosis determination, treatment response prediction, and monitoring disease progression.
One important focus of preventative measures is the use of cancer biomarkers in screening those who have no symptoms but may be at risk of developing the disease. Genetic testing helps to estimate a person’s chance of developing a particular cancer by identifying any mutations in the genes, chromosomes, and proteins that are known to be related to cancer.
Until recently, the FDA had only approved the prostate-specific antigen (PSA) as a genetic biomarker of cancer, specifically prostate cancer. Currently, genetic tests are available for breast, ovarian, colon, thyroid, prostate, pancreatic, kidney, and stomach cancer, as well as melanoma and sarcoma.
While these screening methods do not provide the key to predicting whether someone will certainly develop cancer or not, they can assess whether they are at an increased risk, which helps to set someone on the right path to watching for early warning signs, allowing them to take preventative measures and seek medical attention when the first symptoms present themselves.
Work continues to determine more genetic biomarkers of cancer, and while widespread genetic screening has its benefits, it is argued that in some cases, it can lead to overdiagnosis, resulting in unnecessary surgery and radiation exposure.
In addition to genetic biomarkers for recognizing increased risk, a number of biomarkers have been uncovered that are being used as essential parts in the diagnosis and prognosis determination of cancer.
The overexpression/amplification of the HER2 (ERBB2) gene has been linked with breast cancer. Studies have shown that those with an overexpression of the gene have a better chance of survival when treated with anti-HER2 therapy. Currently, there are several HER2 assays that have been approved by the FDA as a companion diagnostic device.
Other biomarkers are currently being used in a clinical setting, such as BCR-ABL in chronic myeloid leukemia and KRAS mutations in colorectal cancer. While numerous biomarkers have been identified by research, only a fraction of them has been approved by the FDA as clinical indicators of disease, as in most cases, prognostic prediction does not directly influence the clinical design, apart from when it is coupled to specific therapeutic options.
Future developments
Recent years have seen significant advancements in the area of genomics and proteomics, which are generating new candidate markers that could be used for cancer screening. New assays are continuing to enter the market, and such recent developments have seen the establishment of a blood test to check the level of hormone calcitonin that is indicative of Medullary Thyroid Cancer.
In addition, CA-125 has been found to exist in a subset of ovarian cancers, and a test has been developed to highlight early symptoms in those at an elevated risk of developing the disease.
In the future, we can expect the establishment of more assays using new biomarkers of cancer to assist doctors at every step of disease management. From highlighting those who are at risk, to helping with diagnosis and prognosis, and assisting in monitoring disease progression and response to treatment, developments in this area are expected to help people spot cancer in its early stages and to improve treatment outcomes.
Sources:
- Chatterjee, S., and Zetter, B. (2005). Cancer biomarkers: knowing the present and predicting the future. Future Oncology, 1(1), pp.37-50. https://www.futuremedicine.com/doi/full/10.1517/14796694.1.1.37
- Goossens, N., Nakagawa, S., Sun, X. and Hoshida, Y. (2015). Cancer biomarker discovery and validation. Transl Cancer Res, 4(3), pp.256–269. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4511498/
- Henry, N., and Hayes, D. (2012). Cancer biomarkers. Molecular Oncology, 6(2), pp.140-146. https://www.sciencedirect.com/science/article/pii/S1574789112000117
- Sauter, E. (2017). Reliable Biomarkers to Identify New and Recurrent Cancer. European Journal of Breast Health, 13(4), pp.162-167. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5648271/
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