Tumor Marker Test - Role and Drawbacks

What Are Tumor Markers?

Tumor markers are substances (specific proteins) secreted into the blood, body tissues, and urine by cancer cells or normal cells in response to cancer. It helps in detecting tumors at an early stage. High levels of tumor markers are seen in cancers; however, it is also seen in non-cancerous conditions. Tumor markers alone cannot diagnose cancer since they are not specific enough. Some tumor markers are specific to one cancer type, whereas others are associated with multiple different cancer types.

Some of the examples of tumor markers include,

• CEA (Carcinoembryonic Antigen).

• PSA (Prostate-Specific Antigen).

• Thyroglobulin.

• Calcitonin.

• CA 27.29 (Cancer Antigen 27.29 or Carbohydrate Antigen 27.29).

• CA 125.

• CA 19-9.

• CA 15-3.

• Alpha-fetoprotein.

• Human chorionic gonadotropin, etc.

There are two major types of tumor markers:

1. Circulating tumor markers (found in blood, bodily fluids, stool, and urine).

2. Tumor tissue markers (found within the tumor, especially seen in the tumor samples).

An ideal tumor marker should be highly specific (detect specific tumor and avoid false-positive results) and sensitive (detect early tumor and lower false-negative rate). Tumor markers are detected using the “tumor marker test.” A tumor marker test helps in cancer diagnosis, to assess cancer response to the treatment, and to check for cancer recurrence. Tumor marker test in cancer diagnosis has less specificity. Only your healthcare provider can suggest a tumor marker test to detect cancer.

What Is the Role of Tumor Marker Test in Cancer?

The role of the tumor marker test in cancer diagnosis includes,

• To help in cancer monitoring that assesses the cancer risk in individuals.

• To help in cancer diagnosis. For example, the CA-125 tumor marker helps in ovarian cancer diagnosis.

• To determine the cancer stage by assessing the cancer spread (metastasis).

• Helps in cancer prognosis.

• Certain tumor markers help doctors in planning out treatment to which cancer can respond in a better way. For example, breast cancer patients with Her2/neu positive will respond well to Herceptin therapeutic drug treatment.

• Helps in determining the recurrence rate of cancer.

How Is Tumor Marker Test Done?

Tumor markers can be detected through different tests. It includes blood tests, urine tests, and biopsy. The most common tumor marker test is a blood test. If a blood test or urine test for tumor marker testing is carried out, then your blood sample or urine sample is taken and sent for pathological examination. These tests will detect the circulating tumor markers and their association with cancer.

Some tumor markers are associated with specific cancer, but some other tumor markers may have an association with multiple cancers. In a biopsy, tissue from the affected area is removed and sent for pathological examination. It detects the presence of tumor tissue markers. All these tumor marker tests should be carried out only if your doctor asks you to do so.

What Are the Different Tumor Marker Tests Used in Cancer Detection?

Tumor marker tests are used in cancer screening, early detection of cancer, cancer diagnosis, determining the prognosis, assessing how well cancer responds to treatment, monitoring the condition, and determining the cancer recurrence. Cancer diagnosis by tumor marker tests alone does not provide an accurate diagnosis as it has low specificity. Elevated tumor marker levels are not seen in all cancers. Some tumor markers are seen specifically in certain cancers, which helps in the early detection of that particular cancer. Let us see some of the common tumor marker tests used in cancer detection below,

• PSA (Prostate-Specific Antigen) Test: PSA test helps in determining the PSA levels in the blood. Prostate cancer can be detected by elevated PSA levels in the blood. PSA levels with 4.0ng/ml (nanograms/milliliter) and below are considered normal. Prostate cancer patients are seen with PSA levels of more than 4.0ng/ml. But in certain cases, PSA levels less than 4.0mg/ml are also associated with prostate cancer. If your doctor finds your PSA level to be higher, then he will suggest tests furthermore to look for prostate cancer.

• CA (Cancer Antigen) 125 Test: CA 125 test is used in ovarian cancer detection. It is used in cancer monitoring during and after treatment and checks for any cancer recurrence after treatment. The normal range of CA-125 is 0-35 units/ml. Above 35 units/ml of CA-125 is abnormal and can be seen in ovarian cancer. However, high levels of CA-125 always do not mean that you have cancer. So if you have high CA-125 levels, then you may need a further test for cancer diagnosis.

• CEA (Carcinoembryonic Antigen) Test: CEA test detects the amount of CEA in the blood. The normal CEA level is 0-2.5 ng/ml. Levels greater than 10ng/ml are suggestive of any extensive disease and levels greater than 20ng/ml describe that cancer may be spreading. High levels of CEA tumor markers are seen in colorectal cancer, lung cancer, prostate cancer, ovarian cancer, thyroid cancer, etc.

• CA 15-3 and CA 27-29 (Cancer Antigen 15-3 and 27-29) Test: It helps in measuring CA 15-3 and CA 27-29 levels in the blood. These are cancer antigens found in breast cancer. The normal level of CA 15-3 is 30units/ml, and high levels of CA 15-3 are seen in metastatic breast cancer. Normal CA 27-29 should be equal to or less than 38 units/ml. Levels higher than this indicate active breast cancer in individuals.

• Alpha-fetoprotein (AFA) Test: This test measures the amount of alpha-fetoprotein in blood. Normal levels of alpha-fetoprotein are between 10ng/ml to 20ng/ml. Elevated levels of alpha-fetoprotein are seen in liver cancer, ovarian, and testicular cancers.

• Thyroglobulin Test: It is a tumor marker test that helps in guiding thyroid cancer treatment. Normal levels of thyroglobulin are 3-40 ng/ml in a healthy patient. High levels of thyroglobulin are seen in Graves’ disease, thyroiditis, and thyroid cancer. The presence of thyroglobulin in blood after thyroidectomy describes that a part of the thyroid tumor (cancer) or normal thyroid remains. It also detects cancer recurrence in thyroid cancer.

• Human Chorionic Gonadotropin (HCG) Test: HCG as a tumor marker is seen in germ cell tumors, testicular tumors, choriocarcinoma (a malignant tumor that develops from trophoblastic cells), etc.

What Are the Drawbacks of Tumor Marker Tests?

The major drawbacks of tumor marker test include,

1. It cannot detect all cancers as some cancers have no association with tumor markers.

2. A tumor marker test cannot diagnose cancer accurately as it has low specificity.

3. Not used in cancer diagnosis or screening in low-risk patients.

How Reliable Are Tumor Marker Tests?

Tumor marker tests are not highly reliable in cancer diagnosis. Due to its low specificity, the tumor marker test alone is not enough to diagnose cancer. Your healthcare provider will suggest you have further tests for accurate cancer diagnosis.

Conclusion:

Tumor markers, otherwise known as cancer markers, are used in cancer screening, diagnosis, assessing prognosis, assessing the cancer response to the treatment, monitoring the condition, and checking for cancer recurrence. They are not highly reliable in cancer diagnosis and screening. This is due to its low specificity giving out false-positive or false-negative results. Additional tests may be suggested further by your doctor for diagnosing cancer with high accuracy.