Tumor Marker Testing There are a variety of tests for breast cancer that can be performed on cells of a tissue sample from a newly biopsied or stored tumor.

Tumor marker testing provides the patient and oncologist with vital information about the tumor at the cellular level, expanding traditional pathology reports based primarily on tumor size, appearance and staging of the disease.

Tumor markers are substances often detected in higher than normal amounts in the blood, urine or body tissues of some patients with certain types of cancer.

When to Test The American Society of Clinical Oncology (ASCO) recommends that all women diagnosed with breast cancer should have tumor marker tests.¹

Women who have already had a biopsy and know they didn't receive a tumor marker test for a specific characteristic may want to ask their physician to contact the lab where the sample was sent and request a tumor marker test be performed on the stored tissue sample.

If women are told their sample is no longer being stored, they may want to consider requesting a new biopsy if their tumor still is present or their breast cancer returns.

Why Test Tumor marker testing can help predict how a tumor may behave and help guide the choice of the best treatment options for that particular cancer. Results can help guide timing, extent and selection of breast cancer treatment. Patients should talk to their physicians about their treatment options.

The Testing Process When a woman is diagnosed with breast cancer, her physician will obtain a tissue sample from her tumor during biopsy or surgery and send it to a laboratory for various tests.

Tumor marker tests are performed in a hospital's pathology laboratory or sent out to an independent laboratory.

The tests examine tumors to reveal the presence or absence of markers on the surface of the cell or in its nucleus, such as hormone receptors for estrogen (ER) and progesterone (PR) or human epidermal growth factor receptor-2 (HER2) protein overexpression or gene amplification.

A trained pathologist or technologist will evaluate the tumor sample and report results to the patient's physician.

Types of Tests

• Estrogen Receptors (ER) — Studies have shown that estrogen, one of the female sex hormones, often regulates the growth of breast cancer. Knowledge of whether a tumor is positive or negative for the presence of estrogen receptors is used for prognosis and patient selection for anti-hormonal therapy.
• Progesterone Receptors (PR) — To help predict the response to hormonal therapy, the presence of the estrogen-regulated progesterone receptor is now determined routinely.
• HER2 — Detects overproduction of HER2 protein and/or gene amplification, both of which contribute to aggressive growth of the cancer and its spread to other parts of the body. HER2 overexpression occurs in approximately 25 percent of women with breast cancer.
  • FISH or fluorescence in-situ hybridization — A gene-based diagnostic test used to identify women whose breast cancer cells carry amplified HER2 genes and therefore make too much HER2 protein. If the test shows a more than normal number of genes, the test is considered HER2 positive. If the test shows a normal number of genes, the test is considered HER2 negative.
  • IHC or immunohistochemistry — A protein-based diagnostic test used to identify women whose breast cancer cells carry overexpressed HER2 proteins caused by too many copies of the HER2 gene. IHC measures HER2 protein overexpression on different levels -0, 1+, 2+ and 3+. If the test is 2+, the NCCN recommends that a FISH test should be conducted to confirm HER2 positive or negative status.2 If the tumor is 3+, it is HER2 positive.
• P53 — p53 is a tumor suppressor gene. Normally, the p53 protein, coded for by the p53 gene stops cells with DNA damage from multiplying until the DNA is repaired naturally or sends the defective cell into programmed cell death. When the p53 gene becomes damaged or mutated, the protein becomes nonfunctional and loses its checkpoint control, allowing cancerous cells to replicate more readily.
• S phase — In the process of cell replication, a cell cycles through a number of stages. After a cell has duplicated its genetic material and divided through the process of mitosis, it may become inactive or it can start another replicative cycle, beginning with the "S," or synthesis phase during which genetic material duplicates again. Using a special technique, the number of cells in the S phase can be detected. A higher proportion of S phase than normal is a measure of how actively a tumor is proliferating.

¹ American Society of Clinical Oncology. ASCO Patient Guide: Understanding Tumor Markers for Breast and Colorectal Cancers.

² National Comprehensive Cancer Network. Clinical Practice Guidelines in Oncology v.2.2007.