Tumor markers like CEA or CA 19-9 are substances, often proteins, that can be found in the blood and sometimes rise when cancer is present or progressing. For example, CEA is often elevated in colorectal cancer, and ctDNA can offer clues about the genetic profile and potential for MRD negative status of certain cancers like melanoma. These tests are sometimes used as tools to monitor disease progression or response to therapy, escalation or deescalation of therapy but they are not perfect.
Tumor markers can fluctuate for reasons unrelated to actual cancer progression, and sometimes these fluctuations create unnecessary alarm. They are not always definitive indicators of how well a patient is responding to treatment. While tumor markers can be useful in specific situations—like when a scan is ambiguous or when a patient has vague symptoms—they are often secondary to more valuable clinical assessments.
Why Clinical and Radiographic Assessments Matter More
When managing stage IV cancers, two factors typically provide the most reliable information on how well treatment is working:
- How you feel: Your clinical symptoms, such as pain levels, energy, appetite, and overall well-being, are crucial indicators of how you are responding to treatment. Improvements in symptoms like fatigue, nausea, or bone pain often provide far more insight into your disease status than a tumor marker number.
- Imaging results: Imaging tests, such as CT scans, offer a “Kodak picture” of what’s happening with your tumor. Are the tumors shrinking, stable, or progressing? Are there any new growths? These scans provide a much clearer and more objective assessment of how well treatment is working than any blood test can.
In many cases, a patient who is feeling better and showing tumor shrinkage on scans is doing well, regardless of small changes in tumor marker numbers.
The Problem with Focusing on Tumor Markers
Tumor markers can create confusion and anxiety, especially when patients have access to their results via electronic health records before meeting with their doctor. A slight rise in CEA or CA 19-9 may seem alarming, but to most oncologists, small variations in these markers are often meaningless. These fluctuations can be due to various factors unrelated to disease progression, such as inflammation, infection, or even laboratory variability.
When patients see these numbers change, they might worry that the cancer is worsening, even though, from a clinical and radiographic standpoint, they may be doing extremely well. As oncologists, we sometimes regret ordering these tests because the numbers can become a distraction from the bigger picture—how well the patient is actually doing. Tumor markers are just one piece of the puzzle, and often, they are not the most important piece.
When Tumor Markers Can Be Helpful
There are situations where tumor markers can be useful:
- Ambiguous imaging results: If a CT scan shows an area of concern but it’s unclear whether the tumor is growing or stable, tumor markers may provide additional information.
- Subtle, nonspecific symptoms: If a patient is experiencing vague symptoms that don’t clearly indicate progression (e.g., mild fatigue or discomfort), but their tumor markers are rising, this might prompt a closer look with a bone or pet or mri scan.
However, in most cases, if a patient is feeling better and the imaging shows improvement, the tumor markers don’t change the overall assessment. The focus should remain on clinical progress and quality of life.
Shifting Focus to What Really Matters: Your Well-Being
Asking a patient, “How are you doing?” is one of the most important questions during cancer treatment. The response provides insight into the patient’s well-being and how they are coping with treatment. Are you in less pain? Is your energy returning? Are symptoms like nausea or bone pain improving? These subjective but powerful indicators of health are far more valuable than a numerical result from a blood test.
Patients often check their electronic health records before a visit and might fixate on small changes in tumor marker numbers. But the reality is that these numbers don’t always reflect what’s happening in your body as accurately as your own experience and what imaging shows. We should all shift our focus from the anxiety-inducing numbers to how your brain and body are telling you that you’re doing.
Tumor markers, while sometimes useful, are often distracting and can create unnecessary anxiety. The real indicators of how well a patient is doing come from clinical assessments and imaging results. If you’re feeling better and the tumors are shrinking or stable, you are likely doing well—regardless of slight variations in a tumor marker. As we navigate cancer treatment together, let’s prioritize what truly matters: how you’re feeling and how the treatment is impacting your life.
About the Author
Dr. Thomas is a distinguished medical professional and a compassionate guide in the field of oncology. With over a decade of dedicated experience as a board-certified medical oncologist/internal medicine specialist, Dr. Thomas has become a trusted expert in the treatment of melanoma, sarcoma, and gastrointestinal conditions. With his many years of experience, he brings a wealth of expertise to the complex and challenging world of oncology. About Dr Thomas – MedOncMD
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