Free Guide to Understanding Signatera Test Results

What the Signatera Test Is and How It Works

The Signatera test is a blood test that looks for circulating tumor DNA (ctDNA) in your bloodstream. Tumor DNA is genetic material that comes from cancer cells. When cancer cells break down or die in your body, they release small pieces of DNA into the blood. The Signatera test uses advanced technology to find these tiny fragments, even when they are present in very small amounts.

The test was developed by a company called Natera and has been used in clinical settings since around 2020. It received FDA clearance, which means the FDA reviewed the test and determined it meets certain standards for accuracy and safety. However, FDA clearance does not mean the test is recommended for everyone or that it works the same way for all types of cancer.

Signatera is different from other cancer tests because it is "personalized." This means the test is customized based on the specific cancer cells from each individual patient. Before the blood test is done, doctors typically collect tumor tissue (usually from surgery) and send it for analysis. Scientists study the DNA in that tumor tissue to identify the unique genetic "signature" of that person's cancer. Then, when the blood test is performed, the laboratory looks specifically for that person's particular cancer DNA signature in the blood.

The testing process itself is straightforward. A nurse or technician draws blood from your arm, just like during a regular blood test. The blood sample is then sent to a laboratory where technicians use special machines and techniques to search for tumor DNA. The lab looks at millions of DNA fragments and tries to find the ones that match your cancer's unique signature. Results typically come back within 1-2 weeks, though this can vary depending on the laboratory and circumstances.

Practical Takeaway: Understanding that Signatera is a personalized blood test that looks for cancer DNA helps you know what to expect during testing and why your results are specific to your cancer type and history.

Understanding Your Signatera Test Results

Signatera results typically come back as one of two outcomes: "detected" or "not detected." These terms describe whether the laboratory found tumor DNA in your blood sample.

A "not detected" result means the laboratory did not find tumor DNA matching your cancer signature in the blood sample. This is often considered a positive finding in the context of cancer treatment. If you have recently finished cancer treatment like surgery or chemotherapy, a "not detected" result may suggest that circulating tumor DNA is not present in your blood at that moment. However, it is important to understand that "not detected" does not mean cancer is completely gone or will not come back. A "not detected" result means the test simply did not find tumor DNA in this particular blood sample on this particular day.

A "detected" result means the laboratory found tumor DNA in your blood that matches your cancer signature. This suggests that tumor DNA is circulating in your bloodstream. Detection could mean several things depending on your situation. If you recently finished cancer treatment, a "detected" result might indicate that some cancer cells remain in your body or that the treatment did not eliminate all cancer cells. If you are being monitored after treatment, a "detected" result might suggest that cancer may be returning. However, "detected" results should always be discussed with your doctor, as they need to consider your complete medical picture, symptoms, and other test results before making any decisions about your care.

Results often include additional information such as the number of tumor DNA fragments found (called "copies per milliliter") or whether the amount detected is above or below a certain threshold. Some results may show trending information if you have had multiple tests over time, showing whether the amount of tumor DNA is increasing, decreasing, or staying the same.

Practical Takeaway: Learn what "detected" and "not detected" mean in your specific situation by reviewing your results with your oncologist, who can explain what the findings suggest based on your treatment history and overall health.

What Signatera Results Can and Cannot Tell You

One of the most important things to understand about Signatera results is what they can and cannot do. The test can detect the presence of tumor DNA in your blood, but it cannot tell you where in your body that DNA is coming from or how much cancer is present. A "detected" result does not tell you whether you have a small amount of cancer cells or a large amount. It does not tell you whether the cancer is in one location or multiple locations. It does not show whether the cancer is growing quickly or slowly.

Signatera results cannot diagnose cancer on their own. If you have not been diagnosed with cancer before, this test should not be used alone to determine whether you have cancer. The test is most commonly used in people who have already been diagnosed with and treated for cancer, to monitor whether treatment was successful or whether cancer may be returning.

The test also cannot predict with certainty what will happen in the future. A "not detected" result does not promise that cancer will not come back. Some people with "not detected" results may still experience cancer recurrence months or years later. Conversely, some people with "detected" results may not develop any signs of cancer. The test shows whether tumor DNA is present in your blood at one moment in time, but it cannot predict the future course of your disease.

Signatera results need to be understood alongside other information about your health. Your doctor will consider your Signatera result along with imaging tests (like CT scans or PET scans), blood work, physical examination findings, and how you are feeling. These pieces of information together create a more complete picture than the Signatera result alone. Different types of cancer may also respond differently to the Signatera test. The test works better for some cancer types than others, and your doctor can explain how relevant this test is for your specific cancer.

Practical Takeaway: Think of your Signatera result as one piece of information rather than the whole story. Use it as a starting point for conversation with your medical team about what your result means for your specific situation.

How to Discuss Your Signatera Results With Your Doctor

When you receive your Signatera results, it is important to have a conversation with your oncologist or cancer doctor about what the results mean. Here are some questions you may want to ask during that conversation.

Start by asking your doctor to explain what your specific result means. Ask whether your result is "detected" or "not detected" and what that means in your particular situation. Ask your doctor what they expected to see in your result based on your treatment and recovery so far. This helps you understand whether the result is surprising or if it matches what your doctor anticipated.

Ask your doctor how your result compares to previous results if you have had multiple Signatera tests. Ask whether the amount of tumor DNA has changed between tests and what that change means. Ask your doctor whether this result changes your treatment plan or follow-up schedule. Some "detected" results may lead to additional imaging or different treatment approaches, while others may not change your immediate care plan.

Ask your doctor about the limitations of this test for your cancer type. Ask whether Signatera is a standard tool used to monitor your particular cancer, or whether it is used less often for your diagnosis. Ask your doctor what other tests or monitoring strategies are also part of your follow-up care. Ask about the time frame for your next test or imaging study and what you should do if you develop new symptoms before that scheduled appointment.

Ask your doctor whether you should share this result with other healthcare providers involved in your care. Ask about any lifestyle changes, monitoring strategies, or next steps that you should be aware of. Do not hesitate to ask your doctor to explain something again if you do not understand it the first time. Your doctor should be willing to explain your results in a way that makes sense to you.

Practical Takeaway: Prepare for your results discussion by writing down questions beforehand, taking notes during the appointment, and asking for clarification whenever you need it.

Interpreting Signatera Results in Different Clinical Situations

The meaning of your Signatera result depends greatly on your specific situation. Understanding these different scenarios can help you make sense of what your result means for you.

After Cancer Surgery: If you recently had surgery to remove a tumor, your doctor may order a Signatera test several weeks after surgery. A "not detected" result at this point suggests that tumor DNA is not circulating in your blood, which is often considered favorable. However, some patients still develop cancer rec