Cancer Can Be Detected With a Blood Test

You’ve probably had a few blood tests over the years to help doctors check things like your blood sugar and cholesterol or, in some cases, even pinpoint infections that could be causing medical issues. But did you know that a blood test can help detect cancer?

While it’s still a developing area, some cancers can already be detected — or at least suspected — through certain blood tests. Knowing how cancer blood tests work and which cancers can be detected can help you understand what to expect if your doctor recommends this type of blood test.

How Will Cancer Show Up in Blood Work?

Cancer cells can release substances into the bloodstream. Blood tests will look for these substances, which may include:

• Changes in blood cells or blood chemistry
• Fragments of DNA from cancer cells
• Proteins or tumor markers made by cancer cells

Tumor markers can be DNA changes, proteins or receptors, that are found in blood, urine or tissue that signal cancer is present in the body. The markers bind to substances such as hormones or growth factors, instructing the cancer to grow, divide and survive.

However, finding these changes doesn’t always mean cancer. Many noncancerous conditions can cause similar results. Because of this, blood tests are usually a first step, not a final diagnosis.

Blood Tests for Cancer

Some blood tests are already used in health care to help detect or track certain cancers, including these:

Cancer type: Prostate

Test name: PSA (prostate-specific antigen)

About the test: This test measures a protein made by the prostate. If a test shows higher-than-average PSA levels, this may suggest prostate cancer. However, higher levels can also be caused by inflammation, infection or an enlarged prostate. PSA testing can lead to unneeded follow-up tests or treatment. That’s why physicians now advise patients to discuss the risks and benefits with their provider before testing.

Cancer type: Ovarian

Test name: CA-125

About the test: CA-125 can reach higher levels in people with ovarian cancer. But these levels can also rise due to noncancer-related causes such as pregnancy, menstruation or other conditions. This is the reason why CA-125 isn’t recommended as a general screening test for all women. It may be used in women with symptoms, a strong family history of the disease or to monitor treatment.

Cancer type: Colorectal (colon)

Test type: Newer blood-based screening tests

About the test: These blood-based tests look for small pieces of DNA that are linked to colorectal cancer. These tests may be an option for some people who can’t or don’t want to complete stool-based tests. Please note that colonoscopy remains the most accurate screening test. If a blood test result is abnormal, further testing is still needed.

Cancer type: Liver

Test name: AFP (alpha-fetoprotein)

About the test: Results from the blood test may be elevated in liver cancer. It’s often used in people with chronic liver disease, such as hepatitis or cirrhosis, who are at higher risk.

AFP testing is usually combined with imaging tests, such as ultrasound, for better accuracy.

Cancer type: Blood cancers and multiple myeloma

Test type: Routine blood work

About the test: Some cancers start in the blood or bone marrow. Routine blood work can sometimes detect early signs of leukemia, lymphoma and multiple myeloma. If the test detects abnormal blood cell counts or unusual proteins, doctors may order more specific tests.

Newer Multi-Cancer Blood Tests

Newer cancer tests are on the horizon. They’re often referred to as multi-cancer early detection (MCED) tests, which aim to detect signals from multiple cancers using a single blood sample. The tests look for cancer-related DNA patterns or other markers.

Early studies are promising, but the tests are still being studied. They are not yet part of standard screening guidelines, and insurance coverage is limited. Doctors are still learning:

• How accurate the tests are
• How to handle abnormal results
• Which patients benefit most

What Blood Tests Can Tell You and What They Can’t

Cancer blood tests have their limitations. It’s important to understand what they can and can’t tell you.

Blood tests can:

• Help guide next steps
• Point to a higher risk of cancer
• Track response to treatment

Blood tests can’t:

• Confirm cancer on their own
• Find all cancers
• Replace imaging or biopsy

Sometimes, a blood test may be abnormal even when no cancer is present. That’s called a false positive. At other times, cancer may be present even if the blood test looks normal, which is called a false negative.

If you have a higher-than-average risk, such as a strong family history of cancer, known genetic risks or chronic health conditions, you may benefit from blood testing. Based on personal risk and medical history, it’s a decision you’ll want to make with your physician.

Most Effective Cancer Screening Methods

The standard cancer screening tests are still the most proven tools for early detection. They include:

• Colonoscopy
• Lung cancer screening
• Mammogram
• Pap test

Blood tests can add useful information, but currently they don’t replace any of these long-time screenings. It’s best not to skip the recommended screening tests. Doing so can delay diagnosis and treatment.

Learn more about oncology and cancer care at AdventHealth, including screening and testing.