Blood-Based Cancer Screening Tests: How They Work and Who They’re For

Your best defense against cancer is early detection—finding cancer early, before you even have any symptoms. Cancer screening lowers your chances of getting and dying from cancer because cancer is easier to treat and cure before it grows and spreads. You are likely familiar with some cancer screenings already, such as mammograms and colonoscopies.

Expanding technology and medical research, sometimes combined with the power of AI, are driving a new explosion of blood cancer screening tests to add to your cancer screening arsenal. This guide will help you prepare for the new frontier of cancer screening options by explaining how blood-based cancer screening tests work and who they are for.

Are There Different Types of Blood Cancer Screening Tests?

Yes. Cancer screening tests look for markers or indicators of a possible cancer, but they very rarely give a cancer diagnosis. Most cancers are more difficult to diagnose and may require several different types of tests or procedures, such as biopsies or imaging tests like a mammogram, to make an official diagnosis.

There are currently four different types of blood cancer screening tests:

1. Cell-free DNA tests

2. Genetic screening tests

3. Complete blood count (CBC)

4. Tumor marker blood tests

5. Circulating tumor cell tests

6. Blood protein tests

Cancer screening tests are important to know about because they help catch cancer early enough to make treatment and even a cure possible.

Blood-based cancer screening tests all differ in what they actually test for. It can be helpful to talk to your healthcare provider or a genetic counselor about the best blood-based cancer screening test for you.

What Are Some Examples of Blood Cancer Screening Tests?

Cell-free DNA cancer-screening tests, such as the GalleriⓇ Multi-Cancer Early Detection Test, look for DNA from cancer cells in your bloodstream. As they are dying, cancer cells sometimes shed their DNA.

Genetic cancer screening tests look for changes in the DNA inside your blood cells, not cell-free DNA outside your cells. These changes, called mutations, are known to increase your risk for cancer. Examples of genetic cancer screening tests are the BRCA1 and BRCA2 tests for breast cancer risk.

Complete blood counts (CBC), done through a simple blood draw in your arm or hand, look for blood or immune system factors related to cancer. CBCs can screen for leukemia or lymphoma, but not for lung, breast, or colon cancer.

Tumor marker tests, such as the prostate-specific antigen (PSA) test, look for chemicals your body releases into your blood every day. Checking for increases to high levels can indicate an increased risk of some cancers. The PSA test is a blood-based cancer screening test used to check prostate health.

Circulating tumor cell tests are a type of liquid biopsy that look for tiny pieces of cancerous tumors that can break off into your bloodstream. Healthcare providers use these types of tests to diagnose whether or not breast, prostate, or colon cancers have spread to other parts of the body.

Blood protein tests screen for changes in protein levels that can be caused by some cancers, such as lymphoma, leukemia, and multiple myeloma. A comprehensive metabolic panel (CMP) blood test can test for some of these proteins.

How Do Blood Screening Tests Work?

Tests for cancer in the blood do not always give you a cancer diagnosis. Instead, they may only tell you that you have a higher or lower risk of having cancer.

You can take a blood screening test through a healthcare provider, at a laboratory, or sometimes at home. Most tests involve you signing a consent form as well as determining whether or not your health insurance will cover the cost of the test.

If you choose a blood-based screening test done at a healthcare or laboratory site, a medical professional will draw your blood, usually from a vein in the back of your hand or inside of your arm. Usually, there are no dietary restrictions before this type of test.

Depending on where and how you take your blood-based cancer screening test, your results should be available in several days to a couple of weeks. For the GalleriⓇ Multi-Cancer Early Detection Test available through Everlywell, you can access your results from your computer two weeks after sending your test kit back to the GRAIL lab. Since understanding cancer screening tests can be difficult and potentially emotional, many people choose to meet with a healthcare provider or genetic counselor to review their test results.

Who Are Blood Screening Tests For?

Blood cancer screening tests are for anyone who wants to find cancer early. Why would you want to find cancer early? Across all cancer types, the earlier you catch cancer, the better your chances of surviving.

When found early, before cancer cells have a chance to grow into a tumor or spread to other parts of the body, a cure is more likely. These liquid biopsies of your blood are one part of what healthcare providers call early detection.

Genetic cancer screening tests can help people who may have cancer running in their family. You might want to talk with your healthcare provider or a genetic counselor if any of the following describe your family:

• Several of your close family members (such as a mother, daughter, and sister) have or have had the same type of cancer.

• Close family members developed cancer at an early age, such as breast cancer or colon cancer, before age 50.

• Family members have two or more types of cancer (such as melanoma, a type of skin cancer, and prostate cancer).

• Having an unusual presentation of a cancer, such as breast cancer in male family members.

A pattern of cancer in families is also called hereditary cancer risk.

There may be some restrictions on who is eligible for blood-based screening tests. Whether or not you meet these criteria may also determine whether or not health insurance covers the cost of your testing. For example, the Galleri Multi-Cancer Early Detection Test is recommended for people who are 50 years and older and have an elevated risk for cancer. Adults ages 22-49 must have one of the following risk factors to take the test:

• Smoking

• Cancer survivor

• Overweight or obesity

• Family history of cancer

• Genetic predisposition

• Occupational exposure

• Environmental exposure

• Autoimmune inflammatory conditions

• Non-autoimmune inflammatory conditions

• Immunodeficiencies

• Solid organ transplant

Additionally, use of Galleri is not recommended in individuals who are pregnant, 21 years old or younger, or undergoing active cancer treatment.

At-Home Blood Cancer Screening Tests

Most of us dread the most well-known cancer screening tests, such as a colonoscopy or mammogram. The time, cost, worry, and inconvenience some cancer screening tests require prevent too many of us from following recommended routine cancer screening guidelines.

Imagine being able to test for cancer from your couch? It is now a reality, thanks to researchers and scientists who have developed several at-home blood cancer screening options. The Galleri test is one such convenient option.

While tests for cancer in the blood don’t give you a free pass to skip your scheduled mammogram, they do add more information about your personal risk for certain types of cancer. Keep in mind that researchers are still studying how accurate liquid biopsy tests actually are. They may report positive or negative results incorrectly. Large studies are currently underway to assess how effective these tests are. In other words, do blood-based cancer screening tests save more lives than if no blood-based cancer screening were done?

Your most important takeaway is to keep doing your recommended cancer screening tests, even if your blood cancer screening test is negative.

Everlywell Helps Make Blood-Based Cancer Screening Tests Available to You

Remember, the key to winning the war on cancer is prevention and early detection. When combined with a healthy lifestyle, blood-based cancer screening tests may help lower your risk for cancer. You can also explore options like the Galleri® Multi-Cancer Early Detection Test, which is designed to help detect cancer signals early.