From the Guidelines
Blood test cancer markers should be used with caution and in conjunction with other diagnostic tools, as they are not definitive diagnostic tests but rather screening methods or ways to monitor treatment effectiveness and cancer recurrence, as recommended by the American Society of Clinical Oncology 1.
Importance of Cancer Markers
Blood test cancer markers are specific substances in the blood that may indicate the presence of cancer. Common markers include:
- PSA for prostate cancer
- CA-125 for ovarian cancer
- CEA for colorectal cancer
- AFP for liver cancer
- CA 19-9 for pancreatic cancer These tests are not definitive diagnostic tools but serve as screening methods or ways to monitor treatment effectiveness and cancer recurrence.
Interpretation of Cancer Markers
It's essential to understand that elevated marker levels don't always mean cancer is present, as non-cancerous conditions can also cause increases. Similarly, normal levels don't guarantee absence of cancer. These tests should be interpreted by healthcare providers within the context of a patient's complete clinical picture, including symptoms, risk factors, and other diagnostic tests.
Monitoring and Follow-up
Regular monitoring of relevant markers is often part of follow-up care for cancer survivors to detect potential recurrence early. For example, a rising PSA level might prompt further investigation for prostate cancer, while increasing CEA levels could suggest colorectal cancer progression or recurrence after treatment, as noted in the 2006 update of recommendations for the use of tumor markers in gastrointestinal cancer 1.
Limitations and Future Directions
Many tumor marker studies fail to include descriptions of how patients were treated or analyses of the marker in different treatment subgroups. The Update Committee hopes that adherence to a recently published set of suggested guidelines for reporting of tumor marker results (designated the Reporting Recommendations for Tumor Marker Prognostic Studies [REMARK] criteria) will provide more informative data sets in the future, as mentioned in the 2007 update of recommendations for the use of tumor markers in breast cancer 1.
From the Research
Blood Test Cancer Markers
- Cancer markers are molecules produced by cancer cells that can help identify the presence of cancer 2
- Commonly used cancer markers include:
- Carcinoembryonic antigen (CEA)
- Carbohydrate antigen 19-9 (CA 19-9)
- Cancer antigen 125 (CA 125)
- Prostate-specific antigen (PSA)
- Alpha-fetoprotein (AFP)
- Lactate dehydrogenase (LDH)
- These markers can be used to aid in diagnosis, staging, and monitoring of treatment for various types of cancer 2, 3
Role of Specific Cancer Markers
- CEA is elevated in colorectal cancer and can be used to monitor disease progression and response to treatment 4
- PSA is widely used in the management of patients with diagnosed prostate cancer, including screening, surveillance, and monitoring response to therapy 5
- CA 125 is commonly used to monitor ovarian cancer, while CA 19-9 is used to monitor pancreatic cancer 3
Limitations of Cancer Markers
- Cancer markers have poor positive predictive value, making them less useful for mass screening 2
- Not all cancer markers are suitable for screening or diagnosis, and their use should be guided by clinical guidelines 3
- Elevated CEA levels can be found in various types of cancer, but its prognostic value is limited in certain contexts, such as androgen-independent prostate cancer 6