Can a Blood Test Detect Breast Cancer Early?

What proactive women should know about this emerging technology—and why the type of blood test matters.

You stay on top of your health. You schedule your screenings, pay attention to your results, and want to understand your options rather than simply wait and see.

So if you've heard about blood tests that can help detect cancer, you may have an obvious question:

How accurate are they at detecting breast cancer early?

The answer is more nuanced than a single number.

Different blood tests look for different biological signals. Some are designed to detect many types of cancer, while others focus specifically on breast cancer. And when it comes to breast health, especially for women with dense breasts, understanding those differences can help you have a more informed conversation with your doctor.

First, not all cancer blood tests are the same

“Blood test for cancer” can sound like one category of test. In reality, these technologies can work very differently.

Some tests search the bloodstream for tiny fragments of DNA released by cancer cells. Others look at RNA or proteins associated with cancer.

Some are designed to look for signals from dozens of cancers at once. Others, including Certitude, are specifically designed around breast cancer.

That matters because a test that performs well across multiple cancers doesn't necessarily perform the same way for early-stage breast cancer.

When you're evaluating a blood-based test, four questions can help you look beyond the headline:

1. What does the test measure?
2. How well does it identify early-stage breast cancer?
3. How well does it identify people who don't have breast cancer?
4. What role is the test designed to play in your care?

Those details can tell you much more than the word “accurate” alone.

Why early-stage performance matters

Cancer can be more difficult for some blood-based technologies to identify at an early stage because smaller, localized tumors may release fewer detectable signals into the bloodstream.

That's one reason it's important to look at stage-specific sensitivity when evaluating a test.

Sensitivity describes how often a test correctly identifies cancer when cancer is actually present.

For example, in clinical data reported for Certitude, the test demonstrated approximately 93% overall sensitivity and 92% specificity for breast cancer.¹ In the study population, sensitivity by stage included:

• Stage 0: 84.6% (11 of 13 cases)
• Stage I: 88.4% (61 of 69 cases)
• Stage II: 96.9% (95 of 98 cases)
• Stage III: 87.5% (14 of 16 cases)
• Stage IV: 100% (2 of 2 cases)

The number of cases at some stages was small, particularly Stage 0 and Stage IV, so those percentages should be interpreted in the context of the study size and other measures of test performance.

The bigger takeaway: when considering a blood-based breast cancer test, ask how it performs specifically in breast cancer and in earlier stages—not simply how it performs across cancer overall.

What does breast density have to do with it?

If you've been told you have dense breasts, you've probably already learned that breast density can make screening more complicated.

Dense breast tissue and some breast abnormalities can both appear white on a mammogram, which can make cancers more difficult to see. False-negative mammograms are more common among women with dense breasts.

That doesn't mean mammography isn't important. Mammograms remain a central part of recommended breast cancer screening.

It does mean you may want to understand whether there are additional sources of information that could support your care.

Blood-based testing approaches the problem differently. Instead of creating another image of the breast, it looks for biological signals in your blood.

Think of it as another layer of insight—not a replacement for your mammogram.

How Certitude is different

Certitude was designed specifically with breast cancer detection in mind, including the challenges women with dense breasts can experience.

After a blood draw, Certitude's technology profiles more than 9,000 proteins and uses AI-based analysis to identify patterns associated with breast cancer.

Why proteins?

Proteins can provide information about biological changes happening in the body. By analyzing thousands of them together, Certitude is designed to recognize a pattern associated with breast cancer.

In women with dense breasts, Certitude also reports a greater than 99.9% negative predictive value in the population studied.

Negative predictive value answers an especially practical question:

If my result is negative, how likely is it that I truly don't have breast cancer?

Predictive values depend on how common the disease is in the population being tested, so that number needs to be understood within the population in which the test was validated. Your doctor can help you understand what your individual result means in the context of your overall breast health.

Dr. Barbara Levy, Clinical Professor of Obstetrics and Gynecology at George Washington University School of Medicine and Health Sciences stated, “99% of the time a negative test means that there is no cancer. No test is 100%, but we can be really confident with 99% because that is really good.”

Does a blood test replace my mammogram?

No.

Certitude is designed to support standard breast screening, not replace it.

Mammography and other imaging provide important visual information about breast tissue. A blood-based test provides a different kind of information by looking at molecular signals.

Your doctor may consider multiple pieces of information—including your imaging results, breast density, age, family history, genetics, symptoms and other risk factors—when determining appropriate next steps.

If an abnormality is suspicious for cancer, additional diagnostic evaluation may still be needed, and a biopsy remains the definitive way to determine whether a breast abnormality is cancer.

The goal isn't necessarily imaging versus blood testing.

It's using the right information for the right clinical question.

What should I ask my doctor?

Being proactive doesn't mean pursuing every test available. It means understanding your options and making informed choices with your healthcare provider.

If you have dense breasts or questions after breast imaging, consider asking:

• Do I have dense breasts, and what does that mean for me?
• Based on my personal risk factors, is mammography enough?
• Would additional screening or testing be appropriate for me?
• Could a breast-specific blood test provide useful additional information?
• How would the result affect what we do next?

The last question is particularly important. A useful test shouldn't simply give you more information—it should help you and your healthcare provider make a more informed decision.

A more proactive approach to breast health

You already make time for your health because you know that staying informed matters.

Advances in blood-based testing are creating another way to gather information about what's happening in the body. But choosing a test requires looking beyond convenience or a single performance number.

Look at what the test was designed to detect. Look at its performance in breast cancer. Look at how it performs in early-stage disease. And understand how the information can fit alongside the screening you're already doing.

For women with dense breasts, Certitude is designed to provide another layer of insight within that existing care journey.

Because being proactive isn't about doing more for the sake of doing more.

It's about having better information to make your next decision with confidence.

Less uncertainty. More confidence.

If you have dense breasts or want to understand whether Certitude could be appropriate for you, talk with your healthcare provider about your breast density, individual risk, and screening options.

Certitude is designed to support care decisions and does not replace recommended breast cancer screening or diagnostic evaluation.