What are tumor markers in blood test?
Health is always a thing that is taken for granted. People will only appreciate the gift of health when they actually experience some form of disease or sickness. There are many forms of health problems that affect people of all ages. One of the terrifying forms of disease affecting health greatly is cancer. It is so terrifying that even mentioning the word ‘cancer’ can send shivers down the spine in a split second. There are more than 100 types of cancer that have been identified. 50% of all cancer cases are actually preventable which means regular health screening should be able to detect it at its early stage. In this article, we will be learning about tumour markers in blood tests that are associated with cancer diagnosis.
Tumour marker is a substance produced by the body as a response to cancer or certain benign conditions. It has traditionally been proteins or other substances that are produced in higher amounts by the cancer cells than the normal cells. In general, tumour markers can be found in the blood, urine, stool, tumour and other tissue or body fluids of a person with cancer. Tumour markers are also known as biomarkers. Some of these tumour markers are specific to one cancer whereas some may be seen in several types of cancer. Testing for tumour markers in blood tests is usually performed by taking a sample of blood to be analysed in the laboratories.
There are two main types of tumour markers: tumour tissue markers and circulating tumour markers. Tumour tissue or cell markers are found in the tumour, typically in a sample of tumour obtained from biopsy. Circulating tumour markers are found in blood, urine, stool or other body fluids. Hence, tumour markers in blood test are classified as circulating tumour markers.
It is true that high tumour marker levels can be a sign of cancer. Tumour marker tests, specifically circulating tumour marker is used for several reasons such as to estimate the prognosis or outcome of the cancer, to determine the stage of cancer, to identify remaining cancer cells after treatment, to identify if the cancer cells have returned after treatment (recurrence), to assess treatment progress and as a monitor to know if a treatment has stopped working or ineffective.
In reality, circulating tumour markers are not enough to diagnose cancer although elevated levels of this marker may suggest a person with cancer. This is because even noncancerous conditions may lead to an increase of certain tumour markers. Plus, people with a particular type of cancer may not have a higher level of tumour marker to be suspicious with the specific cancer. Some cancers do not produce tumour markers that can be found in the blood test. Thus, circulating tumour markers are usually combined with other results such as from biopsy or imaging test to diagnose cancer.
Example of commonly used tumour marker in blood test includes:
1) Calcitonin- One of the hormones produced by thyroid but increased of calcitonin level is associated with medullary thyroid cancer. Calcitonin biomarkers are most often used to diagnose medullary thyroid cancer, to know if treatment for the cancer is working, to check for recurrence possibility and to estimate prognosis.
2) CA 125- Ovarian cancer is the most common cause for elevation of this biomarker but cancers of the uterus, cervix, breast, lung, liver, pancreas, colon and digestive tract may also raise the level. CA 125 is mainly used to monitor how well treatments for ovarian cancer.
3) Beta-2 microglobulin- Increased amount of this biomarker in blood could indicate cancer such as multiple myeloma and lymphoma.
4) Alpha-fetoprotein (AFP)- Elevated level of AFP may indicate liver cancer or cancer of ovary/testicle.
5) Beta-human chorionic gonadotropin (Beta-hCG)- May indicate cancer in testis, ovary, liver, stomach, pancreas and lung.
6) Carcinoembryonic antigen (CEA)- Colorectal cancer is the most common cancer that elevates this tumour marker.
7) Prostate-specific antigen (PSA)- High level of PSA level may indicate prostate cancer but noncancerous conditions such as benign prostatic hyperplasia (BPH) and prostatitis may increase PSA.
It can be concluded that tumour markers play many roles in cancer. From identifying cancer to the ability to assess the outcome of the cancer, tumour markers make it possible. There are a wide range of tumour markers used to describe the many ranges of cancer types. Commonly used tumour markers as mentioned above are just the small portion of tumour markers available.
Since tumour markers can be used to predict response of a cancer treatment and for prognosis, researchers hoped that tumour markers could be used as screening tests to detect cancer early on, even before symptoms are exhibited. This can be a great advantage in better management of cancer and can potentially be a means of prevention.
However, for now, tumour markers may not be suitable for cancer screening due to the low specificity and low sensitivity in detecting cancer. Fret not, many current researches have highlighted other ways to help early cancer detection, providing better effective treatment and to improve accuracy of predicting chance for cancer outcome along with its possible recurrence. It is hoped that in the near future, cancer diseases can be managed well and hopefully lessen patient’s sufferings.