Cancer biological markers, known as cancer biomarkers, are proteins, genes, and other substances present in the human body that can provide information about cancer progression and tumor development. Testing for biomarker presence and activity can be part of the diagnosis, prognosis, and regular monitoring of treatment, and it may also be called tumor testing or tumor marker testing.
In this introduction, we will discuss several key biomarkers for a few types of cancers, including breast cancer and lung cancer. We will also discuss the possibility and usage of biomarker testing in disease diagnosis and monitoring.
Breast cancer
Breast cancer is one of the most common cancers in the United States, in which cancer cell proliferation is found in the breast and lymph nodes of patients. The American Cancer Society estimates it accounts for about 30% of all new female cancers each year, which means that 1 in 3 women diagnosed with cancer is diagnosed with breast cancer. While the disease typically develops in middle-aged and older women, with such high risk of occurrence, a lot of research has been done with the aims of identifying new diagnosis and disease monitoring methods, with the aim to improve patient outcomes.
One of these realms of research is biomarker testing. Breast cancer biomarkers include genetic markers, proteins, and other substances found in the bloodstream and in cancer cells. One example is circulating tumor cells (CTCs) – found in the peripheral blood of breast cancer patients with non-metastatic breast cancer, the investigation of CTCs has gained substantial recognition in clinical practice.
CTCs are tumor cells that break away from the breast cancer tumor and enter the bloodstream. They can migrate to distant sites within the body, which can lead to potential metastases – which is the spread of breast cancer from the breast and lymph nodes to other places in the body, such as the brain, the liver, and the lungs. The detection of CTCs is vital, as studies have shown a notable correlation between the presence of CTCs and poorer patient outcomes.
Other biomarkers that are vital or gaining prominence in breast cancer monitoring are cancer antigens 15-3 and 27.29 (CA 15-3 and CA 27.29), and Thymidine Kinase 1. The measurement of CA15-3, CA 27.29, and TK1 activity in the bloodstream of breast cancer patients can provide insight into the development and progression of the disease.
Lung cancer
Lung cancer is another common form of cancer and the most common in the United States for both men and women on average. The American Cancer Society estimates that there will be about 234,580 new cases of lung cancer in the US in 2024. With lung cancer being the leading cause of cancer death in the country, accounting for about 1 in 5 of all cancer deaths, biomarker testing for lung cancer patients have been researched with the aim to identify mutations within tumors for diagnosed patients.
Tumor biopsies have been the gold standard in lung cancer diagnosis, due to their ability to investigate targted biomarkers such as carcinoembryonic antigens (CEAs), fragments of cytokeratin-19 (CYFRA21-1), squamous cell carcinoma antigens (SCCs), ad neuron-specific enolase (NSE).
With advancements in technology, body fluid biomarkers are also gaining prominence in lung cancer monitoring. Liquid biopsies can explore potential biomarkers such as CTCs, cell-free DNA (cfDNA), circulating tumor DNA (ctDNA), microRNA, and exosomes. These show promise in identifying and monitoring the disease with minimal invasiveness. For example, studies have reported that the plasma concentration of cfDNA in lung cancer patients is eight times higher than those compared to healthy subjects, and a higher presence of cfDNA has a significant association with worse clinical outcomes.
Biomarker testing alone cannot tell the full story
While biomarker testing can provide valuable information on disease progression, it is not the sole metric by which clinicians and healthcare providers measure treatment efficacy and disease development, as there are certain limitations of biomarker testing. These include the lack of standardized assays for some markers, as well as the need for further research to validate biomarker utility more widely.
In cancer diagnosis and monitoring, clinicians typically supplement biomarker testing with screening methods such as PET scans, MRIs, and mammography. They also perform tissue biopsies to more closely examine the behavior of cancer cells. Additionally, review of the patient’s bloodwork can provide a more comprehensive view of the overall health status of individuals, as cancer therapies may produce unwanted side effects such as anemia.
The bottom line
Biomarkers possess the unique ability to identify tumor mutations and provide valuable information for healthcare providers to learn about the status and development of disease. With more advancements in technology in the research and clinical usage of these biomarkers, clinicians can potentially prolong the life of patients and improve treatment outcomes by creating personalized approaches to medicine.
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