Blood tests for breast cancer are done to serve the following purpose:

  • To evaluate the general condition of the patient and to verify if he or she can withstand the treatment or even check for metastasis if any
  • To evaluate the condition of the specific organs to see if there is any spread of cancer to these organs.
  • To find out if breast cancer is dependent on hormones for its  growth
  • To find out if breast cancer is dependent on certain proteins for growth.
  • To see if the person is genetically prone to breast cancer
  • Tumor marker tests are done to detect breast cancer, to check on the prognosis during treatment, and to detect metastasis.

The following blood tests are carried out to rule presence of breast cancer:-

Complete blood cell counts (CBC)

A CBC test is done to evaluate the general condition of the patient. This test is done before and during treatment for breast cancer.

Complete blood count (CBC) measures

  • White blood cell count tells the doctor of the immune system of the patient. A low WBC count will indicate that the patient is vulnerable to infection. An abnormally high WBC count can mean that cancer has spread to the bones and a bone biopsy may be necessary to rule out bone marrow cancer.
  • Hemoglobin level and red blood cell count will indicate the level of iron in the blood. Low hemoglobin levels will indicate anemia and the patient will be treated as such.
  • The platelet count will indicate the ability of the blood to clot in case of bleeding as in surgery.

Knowing these blood counts becomes necessary during chemotherapy and radiotherapy. Chemotherapy and to lesser degree radiotherapy do lower the blood cell counts and therefore, it becomes necessary to test the patient periodically during treatment. Any abnormality is treated promptly to correct the situation.

Blood Chemistry Tests

Blood chemistry tests are done to evaluate the condition of the vital organs in the body like the liver, kidneys, and bones during treatment and after. Breast cancer can affect the function of some organs and these tests, therefore, become necessary.

  • Liver function tests are done to test for levels of the liver enzymes (which are proteins such as SGOT and SGPT) and serum bilirubin. These tests tell the health of the liver and any abnormality will require that you rule out the spread of breast cancer to the liver.
  • Testing for calcium levels will indicate bone health and density and will also indicate kidney health.
  • Blood sugar levels are done to rule out diabetes.

Abnormal blood chemistry levels can indicate that the breast cancer may have spread to the liver or bone and further tests such as a bone scan or a CAT scan may be necessary for further evaluation.

Other special lab tests are done to determine treatment criteria.

Hormone Receptor Test for Breast Cancer

This test is done on the breast tissue that has been removed by a biopsy to determine if hormone therapy for that breast cancer is necessary or not. Certain malignant tumors of the breast require hormones to grow. They, therefore, have receptors on the surface of the breast tumor cells.

They may have receptors for estrogen (ER-positive) or progesterone (PR-positive) or for both. A hormone receptor test is done to find out if these receptors are present or not. A positive test indicates sensitivity to hormones, in which case anti-hormone therapy becomes an option to treat the breast cancer.

HER2/neu Test

HER2/neu is a cancer gene. In 20% to 30% of invasive breast cancers, this gene is amplified and the protein, HER2/neu protein, which it produces, is increased. This test helps to determine whether the cells of the breast cancer that is present in the patient are HER2 positive or not.

HER2 positive test indicates that the tumor has HER2 protein receptors on the surface of its cells. Blocking of these receptors stops the tumor from growing. The chemotherapeutic drug, Herceptin blocks these protein receptors thereby inhibiting the growth of the tumor.

Genetic Tests for Breast Cancer

Gene testing for blood cancer is about identifying a cancer gene in a person through a blood test. BRCA1 and BRCA2 are a type of genes that give stability to the DNA in the cell and prevent mutation and uncontrolled growth of the cells.

They are, therefore called tumor suppressors. When these genes undergo mutation, or when they become cancer genes, there is a development of breast cancer and ovarian cancer. The “BRCA” stands for breast cancer.

In women, besides the risk of breast and ovarian cancer at an early age, mutation of these genes increases the risk of uterine, cervical, colon, and pancreatic cancer.

In men, mutation of BRCA1 and BRCA2 genes increases the risk of breast cancer, testicular, prostate and pancreatic cancer.

Blood Marker Tests for Breast Cancer

CA 15.3: (or CA 27.29:) are two markers whose presence in blood will indicate breast cancer. Tumor markers are proteins manufactured by malignant cells. These proteins and tumor cells circulate in the blood and are found in the blood, urine, and body tissues.

Elevated levels of tumor markers give an indication of cancer. Tumor markers are specific proteins for specific types of cancers. The elevated presence of blood markers CA 15.3: or CA 27.29:  in blood will indicate the presence of breast cancer.

This blood marker test for breast cancer serves the following purpose.

(1) It is used to screen a high-risk population as a blood test to detect breast cancer.

(2) This cancer test will help to know the prognosis of breast cancer during treatment.

(3) This test will also allow the doctor to monitor the patient after treatment to look for any remission of cancer.

(4) To detect any spread of cancer to other parts of the body.


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