Multi-cancer Detection (MCD) Tests

Multi-cancer detection (MCD) tests, also known as multi-cancer early detection (MCED) tests, are a new type of lab test that looks for signs of many types of cancer from one sample. These tests are not yet FDA-approved, but some are now available. Understanding how they work and what they can and can’t find can help you decide whether to get one.

What do MCD tests look for?

MCD tests check blood or other body fluid (such as urine or saliva) samples for signs of cancer, such as pieces of DNA, RNA, or proteins from abnormal (cancer) cells. If the test finds something abnormal, it might mean the person has cancer.

Some MCD tests suggest where the cancer started. Others may only show that cancer could be present, without identifying a probable type or location.

Can MCD tests tell for sure if someone has cancer?

No, MCD tests do not diagnose cancer. If a test result is positive, more tests will be needed to confirm if cancer is present, what type it is, and where it’s located.

Like all medical tests, MCD test results can sometimes be hard to interpret or even be wrong. (See What do we still need to know about MCD tests? below.)

Why are MCD tests being developed?

The main goal of MCD tests is to find cancers earlier, ideally before symptoms appear. Cancer detected early is more likely to be treated successfully.

Screening is testing for cancer before a person has symptoms. Currently, proven screening tests exist for only a handful of cancers (including breast, cervical, colorectal, prostate, and lung cancer). Getting these tests as recommended helps find and treat these cancers earlier than if they’re found once they start to cause symptoms.

But most types of cancer don’t have proven screening tests. In fact, nearly half of all cancers diagnosed each year are cancers with no recommended screening tests. These cancers are often found at later stages, when they can be harder to treat.

MCD tests might be able to find a wider range of cancers early, hopefully before a person has any symptoms.

Are MCD tests FDA-approved?

MCD tests have not been cleared or approved by the FDA yet. However, some are available as lab-developed tests (LDTs) under the Clinical Laboratory Improvement Act (CLIA) regulations, which means doctors can order them. Examples include the Galleri test and the Cancerguard test.

The companies that make these MCD tests are gathering data to seek FDA approval. But more research is needed before these tests can be recommended for widespread use in people with no symptoms of cancer.

Many other MCD tests are now being developed as well.

Even if they are approved at some point, MCD tests do not replace current screening tests (such as mammograms for breast cancer, Pap tests and HPV tests for cervical cancer, stool tests and colonoscopy for colorectal cancer, the PSA blood test for prostate cancer, and low-dose CT scans for lung cancer). MCD tests might be used along with current screening tests, as well as to help find cancers for which there aren’t screening tests yet.

Will health insurance pay for MCD tests?

Although some MCD tests are now available, most insurance plans, including both Medicare and private plans, don’t cover them at this time.

Most people will have to pay out-of-pocket (typically at least several hundred dollars) for these tests. Additional testing that may be recommended if an MCD test result is positive can also be costly, and it’s not yet clear if insurance would cover these costs.

What do we still need to know about MCD tests?

Here are some of the questions about MCD tests that still need to be answered.

• How accurate are MCD tests? Much still needs to be learned about the accuracy of these tests. A test that checks for many cancers may detect some types of cancer better than others.
• Who should be tested? It’s not yet clear if MCD tests will be best used for general cancer screening, or for specific groups, such as people at higher cancer risk because of age, sex, family history, exposures, or other factors. A person’s life expectancy or their willingness and ability to follow up on test results might also matter.
• How early can an MCD test detect a cancer? Research is being done to determine if MCD tests can find cancer early enough to improve treatment outcomes compared to cancers found after symptoms have started.
• Do MCD tests save lives? It’s not yet known if MCD testing reduces the number of deaths caused by cancer. Researchers still need to learn if earlier detection with MCD tests and treating these cancers earlier improves outcomes, including the risk of dying from cancer.
• What should happen after a positive MCD test result? After a positive MCD test result, doctors will likely need to do additional tests. Because MCD tests are new, doctors are still learning which tests should be done after a positive MCD test result—and how to proceed if those follow-up tests don’t find cancer.
• How often should the test be done? The ideal amount of time between MCD tests still needs to be determined. Different cancers can grow at different rates. Waiting too long between tests might miss some cancers, but having a test too often (when it isn't needed) could lead to anxiety and be a waste of important medical resources.

Along with needing to know more about the best ways to use MCDs, there is the chance of having possible inaccurate or unclear test results.

• What about false-positive results? So far, research has shown that over half of people with positive MCD test results are found not to have cancer when further testing is done, known as a false-positive result. False-positive test results can cause anxiety and lead to unnecessary follow-up tests.  
• What about false-negative results? A false-negative result (a test result being negative even when a person has cancer) might give a false sense of security and could delay a cancer diagnosis. Although a negative MCD test result usually means a person has a very low risk of having cancer at that time, it’s important not to ignore new symptoms and signs that could be caused by cancer. Even with a negative MCD test result, it’s still important to continue to have recommended screening tests on schedule. 

Expert guidance for shared decision-making with MCD testing

At this time, there are no clinical practice guidelines or official recommendations for using MCDs in the United States.

Because of the potential importance of these tests, cancer screening experts have developed MCD guidance for primary care (family) doctors and their health care teams to help guide discussions with patients. The key points for discussion are not recommendations for using MCD tests, but they are designed to encourage shared decision-making between people and their doctors when considering screening with one of these tests.

The importance of shared decision-making

Because there are so many uncertainties about MCD tests, it’s important that you talk with your doctor about whether testing is right for you. This is called shared decision-making. Shared decision-making means you’re getting enough information about MCDs to make an informed decision about whether or not to use them.

MCD testing conversations should include information about the potential benefits, limits, harms, and uncertainties around MCD testing.

It’s also important to consider your personal values and preferences. For example, if you’re not willing to have more tests if you have a positive MCD test result, you might not be a good candidate for MCD testing.

It’s important to remember that MCD tests should not replace recommended screenings for breast, cervical, colorectal, lung, and prostate cancers.

Questions to ask your doctor or health care team about MCD testing

If you are thinking of getting an MCD test, here are some key questions to ask. They can help guide the conversation with your doctor and health care team.

• What is an MCD test?
• What MCD tests are available?
• Would I be a good candidate for MCD testing?
• How much does the test cost? Will my employer or insurance cover it?
• What are the possible benefits of MCD testing?
• What are the possible limits, harms, and uncertainties of MCD testing?
• How often would I need to get the test?

What work is the American Cancer Society (ACS) doing related to MCDs?

The American Cancer Society is addressing the promise and use of MCD tests on several fronts.

ACS research on MCD testing

ACS funds and conducts research to support advancing the potential use of MCD tests. ACS believes that if these tests are successful, they could save many lives that would otherwise be lost. ACS researchers have also worked with developers of some of these tests to provide guidance and, in some instances, to allow them to measure the accuracy of their tests within our population studies (through research collaborations).

Advocacy for access to MCD tests

The American Cancer Society Cancer Action Network (ACS CAN) works to pass laws and regulations across the country that could benefit people with cancer or who might have cancer, such as the Nancy Gardner Sewell Medicare Multi-Cancer Early Detection (MCED) Screening Coverage Act. This act would create a pathway for older adults and others on Medicare to get these tests if they are approved by the FDA and shown to have clinical benefit.