June 19, 2018

How Blood Tests Can Be Used to Detect Cancer

Early Cancer Detection

In 2018, nearly 1.7 million new cases of cancer are expected to be diagnosed in the United States alone, which will result in an estimated 609,640 deaths. With statistics this profound, chances are high that you or someone you know has been—or will be—diagnosed with cancer in your lifetime. In fact, recent facts and figures from the American Cancer Society show that nearly 40% of men and women in the US will, at some point, be diagnosed with cancer.

The most common cancer diagnoses in order of prevalence 1

  • Breast
  • Lung and bronchus
  • Prostate
  • Colon and rectum
  • Bladder
  • Melanoma of the skin
  • Non-Hodgkin lymphoma
  • Thyroid
  • Kidney and renal
  • Leukemia
  • Endometrial
  • Pancreatic

One reason cancer mortality remains high is that screening for and detecting all the specific types can be difficult. In addition to being lengthy, expensive, and complex, common screening methods like lab tests and imaging procedures are often only designed to detect a certain type of cancer, such as mammograms for breast cancer and colonoscopy for colorectal cancer. Along with prostate, cervical, and lung cancer, these 5 are the only cancers commonly screened for in the general population.

Cancer blood testing today

Cancer screening using blood testing could make early detection more accessible; however, currently available cancer blood tests are hindered by limited accuracy and only apply to specific cancers. Some common blood tests used in cancer today are:

  • The complete blood count (CBC) test measures the number of blood cells and/or abnormal cells within the body.
  • Blood protein testing is effective in identifying abnormal immune system proteins commonly present in multiple myeloma. A blood protein test, also known as electrophoresis, is often the most reliable way to study and examine the health and vitality of proteins in the blood.
  • Tumor-marker tests such as PSA testing in prostate cancer, detect the chemicals created by cancerous tumor cells. Because tumor markers are also produced by normal cells, this test is typically used in conjunction with other tests to make a firm cancer diagnosis.
  • Circulating tumor cell tests are used for detecting cells floating in the bloodstream that have broken away from the initial cancer site. This test is often used to monitor patients with breast, colorectal, and prostate cancer.

Even though these tests are scientifically proven, their results are not always accurate and must be closely read and interpreted.Variables like body type and diet can sometimes influence test results. In order to make a definitive diagnosis, most forms of cancer require a biopsy. A biopsy is an invasive surgical procedure in which doctors remove a small piece of tumor tissue in order to diagnose, and in some cases determine how best to treat, a given cancer.

How can blood work detect cancer better?

In many cases, cancer can be present in the body long before any symptoms appear. Unfortunately, many people never consider getting tested for cancer until their symptoms become obvious, at which point the tumor may already have grown and spread. Recently, however, scientists have discovered that, even in the early stages of tumor growth, small amounts of DNA, RNA, and proteins are released into the blood. These fragments can come from both the tumor as well as the body’s own surveillance system, which includes infiltrating immune cells. Patterns among these cell-free molecules could provide the earliest indicators of cancer—if they can be identified.

Next-generation cancer blood tests

Companies like Freenome are now experimenting with new methods to digitize and examine a much broader range of molecules in the blood than ever before possible. While this creates an unprecedented amount of data that can be analyzed for patterns associated with specific types of cancer, it’s so complex that specially-designed artificial-intelligence (AI) is needed to draw meaningful conclusions.

AI pattern recognition among billions of cell-free biomarkers should enable doctors to detect cancer much earlier, and with greater sensitivity and specificity than current blood tests. So thanks to advanced medical technology and ongoing cancer research, it won’t be long before multiple life-threatening cancers can be detected using a simple AI-powered blood test.

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  1. American Cancer Society: Cancer Facts and Figures 2018. Atlanta, Ga: American Cancer Society, 2018. Also available online. Last accessed February 26, 2018.


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