Blood Tests Used to Diagnose Cancer

While no blood test can diagnose cancer, some blood tests can aid in the diagnosis of cancer. If cancer is suspected, blood tests may be ordered. There are also blood tests used to screen for cancer or monitor the return of cancer after treatment.

Blood Tests Alone Cannot Diagnose Cancer

There are no blood tests that can diagnose cancer. Additional testing is required to diagnose cancer. Talk to your healthcare provider about your results and if further tests will be performed.

blood test vials examined
krisanapong detraphiphat / Getty Images.

krisanapong detraphiphat / Getty Images

Complete Blood Count (CBC)

A complete blood count test (CBC) checks the levels of cells produced by bone marrow in the blood, such as

  • Red blood cells
  • White blood cells
  • Platelets

CBC tests are performed during cancer diagnosis, particularly for leukemia and lymphoma, and throughout treatment to monitor results. 

CBC tests can also:

  • Indicate whether cancer has spread to bone marrow.
  • Detect potential kidney cancer through an elevated red blood cell count.
  • Monitor the effects of chemotherapy

Chemotherapy treatment affects cell division in cancer cells and bone marrow cells, which can cause bone marrow suppression. A CBC test can monitor the following:

  • Anemia due to low red blood cell levels
  • Neutropenia from low levels of white blood cells increasing infection risk
  • Thrombocytopenia when platelet levels are low

Comprehensive Metabolic Panel (CMP)

A comprehensive metabolic panel (CMP) provides your healthcare provider with information on your:

  • Fluid balance
  • Electrolyte levels
  • Blood sugar
  • Protein levels
  • Liver functioning
  • Kidney functioning

A CMP, performed with a singular blood draw, consists of 14 blood tests and can help assess your general health and diagnose and manage cancer.

A CMP can indicate certain types of cancer, depending on results. For example:

  • High calcium (hypercalcemia) may be suggestive of lung, breast, esophageal, oral, kidney, ovarian, uterine, and cervical cancer, as well as lymphoma and multiple myeloma.
  • Low blood glucose with hypercalcemia and raised liver enzyme may be a sign of liver cancer.
  • High glucose levels can indicate pancreatic cancer.

A CMP test can also be used to monitor how cancer treatments affect your kidney or liver function and how calcium levels may affect your heart function and bones.

Tumor Blood Markers

When a tumor or cancer cell is in the body, substances released by them can be measured. These are called tumor blood markers and can monitor cancer progression, recurrence, diagnosis, screen, and stage cancer.

Limitations of Blood Tumor Markers

An abnormal blood tumor marker result does not necessarily mean you have cancer. For example, only about one in four abnormal prostate-specific antigen (PSA) results is due to cancer, and approximately 15% of prostate cancer is missed.

There are many reasons for abnormal PSA levels. Similarly, carcinoembryonic antigen (CEA), a tumor marker used in colon cancer, is only made in 70 to 80% of colon cancers. Therefore, 20 to 30% of people with colon cancer will not have a raised CEA level.

Tumor blood markers aren't typically able to diagnose cancer independently but can be combined with other tests for diagnosis. Tumor blood markers can also:

  • Monitor the progression of cancer to see whether or not treatments are working
  • Determine whether or not cancer has recurred after treatment or surgery
  • Help determine the cancer stage
  • Help determine the best treatment
  • See if a tumor is growing or spreading (metastasized) to other parts of the body

Positive test results may be due to a noncancerous condition. Your doctor can help you understand the results of tumor blood markers and what they mean for you.

Tumor Blood Markers Tests
Test Purposes Diseases
5-HIAA Diagnosis, monitoring Carcinoid tumors
Alpha-fetoprotein (AFP) Diagnosis, staging, prognosis, treatment response Liver cancer; germ-cell tumors
Beta-2-microglobulin (B2M) Prognosis, treatment response Multiple myeloma, chronic lymphocytic leukemia, and some lymphomas
Beta-human chorionic gonadotropin (Beta-HCG) Staging, prognosis, treatment response Choriocarcinoma, germ cell tumors
CA 15-3 Treatment response, recurrence Breast cancer
CA 27.29 Treatment response, recurrence, metastasis Breast cancer
CA19-19 Treatment response Pancreatic, gallbladder, bile duct, gastric cancers
CA 125 Diagnosis, treatment response, recurrence Ovarian cancer
Calcitonin Diagnosis, treatment response, recurrence Medullary thyroid cancer
CD20 Assess treatment Non-Hodgkin lymphoma
CEA Diagnosis, treatment response, recurrence, metastasis Colorectal cancer, some others
Chromogranin-A Diagnosis, treatment response, recurrence  Neuroendocrine tumors
Gastrin Diagnosis, treatment response, recurrence Gastrin-producing tumor (gastrinoma)
Lactate dehydrogenase (LDH) Staging, prognosis, treatment response Germ cell tumors, lymphoma, leukemia, melanoma, neuroblastoma
Neuron-specific enolase (NSE) Diagnosis, treatment response Small cell lung cancer, neuroblastoma
Prostate-specific antigen (PSA) Diagnosis, treatment response, recurrence Prostate cancer
Thyroglobulin Treatment response, recurrence Thyroid cancer

Genomic Testing

Genetic testing helps you and your healthcare provider understand how likely you are to develop cancer during your lifetime by checking for gene mutations. These gene mutations are specific inherited changes to a person's genes, which would be associated with the risk of developing cancer. Inherited gene mutations contribute to approximately 5 to 10% of all cancers.

While most genomic tests are performed on tissue biopsy, a few blood tests are used for this purpose. 

Genetic testing cannot tell you if you will develop cancer for certain but can reveal if you have a higher risk than the average population. If you have a family history that points to genetic causes of cancer or if these results might help with a diagnosis or treatment of cancer, your healthcare provider may recommend genetic testing.

While there are several options when it comes to genomic testing for cancers, these three below are the most common:

Genomic Tests
Test Purpose Disease
BRCA1 Determine presence of gene mutation BRCA1, assess targeted therapy Ovarian cancer, breast cancer, and other cancers
BRCA2 Determine presence of gene mutation BRCA2, assess targeted therapy Ovarian cancer, breast cancer, prostate cancer and other cancers
Philadelphia chromosome Determine presence of gene mutation, assess risk, assess targeted therapy chronic myelogenous leukemia, acute lymphocytic leukemia

Electrophoresis

Serum protein electrophoresis tests antibodies in your blood to search for abnormalities that indicate myeloma cells are present. Myeloma cells produce a monoclonal antibody, meaning all the same. The discovery of this antibody in the blood helps to diagnose multiple myeloma. 

Circulating Tumor Cell (CTC) Test

A circulating tumor cell test (CTC) can check for blood biomarkers that show whether normal cells are transforming into cancer cells. CTC tests can help diagnose and screen patients who have a risk of developing cancer, such as a family history of the disease.

CTC tests are helpful in the early detection of cancer as well as monitoring treatment effectiveness over time. The only test currently approved for this purpose is called CellSearch CTC, which offers different prostate, colorectal, and breast cancer assays.

A Word From Verywell   

Ask your healthcare provider for help interpreting any results from blood tests. Further testing will likely be done before any diagnosis is made. Although cancer testing is stressful and frightening, it’s important not to jump to conclusions. Additional tests and discussions with your practitioner will help determine your diagnosis.

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Article Sources
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  1. American Society of Clinical Oncology. Understanding your complete blood count (CBC) tests. June 2019.

  2. OconoLink. Comprehensive metabolic panel. Updated July 22, 2020.

  3. MedlinePlus. Comprehensive metabolic panel (CMP). Updated December 10, 2020.

  4. National Cancer Institute. Genetic testing for inherited cancer susceptibility syndromes. Updated March 15, 2019.

  5. American Cancer Society. Tests to find multiple myeloma. Updated February 28, 2018.

  6. Ried K, Eng P, Sali A. Screening for circulating tumour cells allows early detection of cancer and monitoring of treatment effectiveness: an observational studyAsian Pac J Cancer Prev. 2017;18(8). doi:10.22034/APJCP.2017.18.8.2275