Can Cancer Be Detected in Blood Tests?

Blood tests may indicate if other organs of the body have been affected by cancer.

When a person is suspected to have cancer, doctors may perform a variety of tests to help diagnose cancer. Different types of blood tests are done to check for abnormal cells, cancer cells, proteins, tumor markers, or other substances made by the cancer cells. This helps determine if a person has cancer or any precancerous condition.

Blood tests may also indicate if other organs of the body have been affected by cancer. Except for blood cancers, blood tests alone cannot diagnose cancer. However, they can give clues about the health condition of the body.

Along with blood tests additional tests may be required to accurately diagnose cancer.

Different types of blood tests used to diagnose cancer include:

Complete blood count (CBC)

A CBC test measures the size, number, and maturity of different types of blood cells found in the blood. It measures the number of red blood cells, white blood cells (neutrophils, eosinophils, basophils, monocytes, and lymphocytes), and platelets in the blood. This test also measures levels of hemoglobin and hematocrit in the blood. Blood cancer may be diagnosed if abnormal cells or too many or too few of a type of blood cell are found in the blood.

CBC tests can:

• Diagnose certain blood cancers, such as leukemia and lymphoma.
• Indicate the spread of cancer to the bone marrow.
• Determine potential kidney cancer.
• Monitor the effects of chemotherapy.

Circulating tumor cell (CTC) test

This test helps detect, identify, and count circulating tumor cells that have detached from the original tumor site and entered the bloodstream. This diagnostic test may be used to monitor metastatic breast, colorectal, and prostate cancers.

Flow cytometry

Flow cytometry is used to diagnose certain types of cancers, such as leukemia and lymphoma, and evaluate the risk of recurrence. The blood sample is treated with special antibodies and passed in front of a laser beam. If these antibodies get attached to cells, the cells give off light. The type of cancer cell is identified based on either the presence or the absence of certain protein markers (antigens) on a cell's surface.

Cytogenetic analysis

A sample of blood cells is examined under a microscope to look for chromosomal changes. Cytogenetic analysis detects alterations in chromosomes and may identify actual genes that have been affected. The findings help diagnose specific types of blood cancers.

Gene expression profiling

This test helps identify cancer subtypes and risk factors. Gene expression profiling is mostly used as a research tool and in designing treatment protocols. This test uses a technique called microarray analysis to identify combinations of genes that are turned on or off in response to specific conditions. The test results help classify tumors and predict response to treatment and risk of disease relapse.

Immunophenotyping

Immunophenotyping identifies a specific type of cell in a sample of blood. Immunophenotyping can distinguish myeloid leukemia cells from lymphocytic leukemia cells, normal lymphocytes from leukemic lymphocytes, and B-cell lymphocytes from T-cell lymphocytes. This procedure helps determine the best cancer treatment.

Karyotype test

A karyotype test uses the 46 chromosomes of a cell to identify and evaluate changes in arrangement, size, shape, and number in a sample of blood. A dye called Giemsa may be used to easily view the banding pattern of chromosome pairs. This is also referred to as G-banding.

Blood chemistry test

Blood chemistry involves a group of tests that provide information about the underlying cancer.

Depending on the type of panel, these tests can measure:

• Electrolyte balance
• Protein (such as albumin, beta 2-microglobulin, immunoglobulins [IgM, IgG, and others], and lactate dehydrogenase [LDH])
• Blood glucose
• Cholesterol
• Liver and kidney functions
• Hormones (such as thyroid hormone)

The results of the blood chemistry tests can indicate certain types of cancers, such as:

• High glucose levels can be a sign of pancreatic cancer.
• Hypercalcemia may indicate paraneoplastic syndromes due to the spread of cancer to the lung, breast, esophageal, oral, kidney, ovarian, uterine, cervical cancer, lymphoma, and multiple myeloma.
• Low blood glucose with hypercalcemia and raised liver enzymes may be a sign of liver cancer.

Genetic testing helps to understand if a person has a higher risk of developing cancer during their lifetime by checking for gene mutations. While most genomic tests are performed on tissue biopsy, a few blood tests are used for this purpose.

Common genomic tests and their indicative cancers are:

• BRCA1: Ovarian cancer, breast cancer, and other cancers
• BRCA2: Ovarian cancer, breast cancer, prostate cancer, and other cancers
• Philadelphia chromosome: Chronic myelogenous leukemia and acute lymphocytic leukemia
• Electrophoresis: Serum protein electrophoresis tests for monoclonal antibodies in the blood sample. Myeloma cells produce a monoclonal antibody. The presence of this antibody in the blood helps to diagnose multiple myeloma.
• Tumor marker tests: Tumor markers are substances produced by tumor cells in high quantities, which can be detected when their levels are elevated in the blood. Tumor markers help diagnose cancer, monitor how well the body is responding to treatment, or check if cancer has recurred. The tumor marker test is combined with other tests, such as biopsies, to make a definitive diagnosis of cancer.
  • Tumor markers used for diagnosing cancer and their associated cancer include:
    • Prostate-specific antigen (PSA): Prostate cancer
    • Cancer antigen-125 (CA-125): Ovarian cancer
    • Calcitonin: Medullary thyroid cancer
    • Thyroglobulin: Thyroid cancer
    • Alpha-fetoprotein (AFP): Liver cancer
    • Beta-human chorionic gonadotropin (Beta-hCG): Germ cell tumors such as testicular cancer and ovarian cancer
    • Beta-2-microglobulin (B2M): Multiple myeloma, chronic lymphocytic leukemia, and some lymphomas
    • CA 15-3/CA 27-29: Breast cancer
    • CA 19-9: Pancreatic cancer, gallbladder cancer, bile duct cancer, and gastric cancer
    • Carcinoembryonic antigen (CEA): Colorectal cancer
    • Chromogranin A (CgA): Neuroendocrine tumors
    • Human epididymis protein 4 (HE4): Ovarian cancer
    • Immunoglobulins: Multiple myeloma and non-Hodgkin lymphoma
    • Neuron-specific enolase (NSE): Lung cancer
    • CD20: Non-Hodgkin lymphoma