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Hormone
Receptor Status
Physicians often examine hormone
receptors in breast cancer cells at the time of biopsy or breast
surgery to determine whether estrogen receptors (ER-positive) or progesterone receptors
(PR-positive) are present. Patients whose cancers have ER or PR-positive receptors tend to
have a better prognosis than patients whose cancers do not have these receptors. Cancers
with ER or PR-positive receptors are also much more likely to respond to chemotherapy or hormone treatment.
Breast cancer cells that express
ER-positive receptors in their nuclei also tend to respond better to hormonal
manipulation. For example, the drug tamoxifen is used to block
the female hormone estrogen from estrogen receptors, thus slowing the growth and
reproduction of cancerous cells. Researchers know less about PR-positive receptors but
have noticed that cells that contain ER-positive receptors often contain PR-positive
receptors too. If a cell contains a PR-positive receptor but no ER-positive receptors, a
patient’s prognosis may be worsened.
HER2 (human epidermal growth factor
receptor 2), a protein receptor found on the surface of cells, is a key component in
regulating cell growth. When the HER2 gene (sometimes written HER2/neu) is altered, extra
HER2 receptors may be produced. This over-expression of HER2 causes increased cell growth
and reproduction, often resulting in more aggressive tumor cells. HER2 protein
over-expression affects 25% to 30% of breast cancer patients. A new drug, herceptin, has recently been approved by the U.S. Food and Drug
Administration (FDA) to treat women with metastatic breast cancer who over-express HER2.
Metastatic breast cancer is cancer that has spread past the breast and underarm lymph
nodes.
Physicians may test tumor tissue for
HER2 over-expression at the time of breast biopsy or surgery.
Testing may also be done on stored tumor tissue from previous biopsy. To test for HER2
over-expression, the tumor tissue will be stained by a specific solution. A pathologist
will then examine the tissue, checking for highlighted areas where high levels of
over-expression are present. Depending on the level of staining, the tumor tissue sample
may be classified as HER2 positive.
It is estimated that 200,000 HER2
diagnostic tests are performed each year. Women are encouraged to be tested for HER2
over-expression at the time of breast cancer diagnosis since results of the test may help
determine a course of treatment.
DNA
Cytometry
Cytometry is the process of
counting and measuring a patient’s cells. DNA cytometry involves measuring a breast
tumor’s DNA to help predict the tumor’s aggressiveness. Flow cytometry is
one type of DNA cytometry in which lasers and computers are used to measure the amount of
DNA in cancer cells suspended in liquid as they flow past a laser beam. A second type of
DNA cytometry, image cytometry, involves using computers to analyze digital images
of the cells from a microscope slide. Both flow cytometry and image cytometry measure the
DNA ploidy (amount of DNA) of cancer cells. Ploidy is a marker that helps predict how
quickly a cancer is likely to spread. Cancers with the same amount of DNA as normal cells
are called diploid and those cancers with either more or less than that amount are called
aneuploid. About two-thirds of breast cancers are aneuploid.(1) Several studies
have shown that aneuploid cancers tend to be more aggressive than normal cancers.
Flow cytometry can also measure a
tumor’s S-phase (the percentage of cells in a sample that are in the synthesis stage
of cell division). Many cells in the S-phase indicate that the breast tissue is growing
fast and that the cancer is likely to be more aggressive than normal cancers. Image
cytometry can also estimate the growth rate of a cancer when combined with special
antibody tests of the breast tissue.
Additional
Resources and References
(1) The American Cancer Society provides
detailed information on histologic grades at http://www3.cancer.org/cancerinfo/main_cont.asp?st=ds&ct=5.
To learn more about HER2 and how the
drug herceptin helps treat breast cancer patients who over-express the HER2 gene, please
visit http://www.imaginis.com/breasthealth/herceptin.asp
Updated: May 4, 2008
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