If your doctor finds breast cancer, several other tests may be performed to determine what type of cancer it is and how far it has advanced. This information is vital for choosing the best treatment plan.
Not all breast cancers are the same. There are several types of breast cancer, and sometimes more than one type is seen in the same patient. Sometimes the biology of the tumor changes if it spreads (metastasizes) to another part of the body. Evaluating a tumor's microscopic characteristics is also very important to help evaluate whether the cancer is likely to metastasize and what type of therapy is most appropriate.
If you have recently learned that you have breast cancer, it may be possible to take at least a few days — and perhaps a few weeks — to learn about your treatment options and to think about which treatment is best for you, both medically and personally.
Features of Breast Cancer
Several factors are important in determining the stage of your breast cancer and the best treatment approach.
The stage of a cancer, sometimes referred to as TNM, is used to determine the type of treatment a woman should receive. It is calculated based on several factors:
- Size of the tumor (T)
- Whether or not the cancer has spread to the axillary (underarm) lymph nodes, and if so, to how many (N)
- Whether or not the cancer has spread to other lymph nodes of the neck or chest area
- Whether or not the cancer has spread (metastasized) to other parts of the body (M)
Tests for determining how far a breast cancer has spread include a chest x-ray and blood tests, as well as bone scans, CT scans, PET scans, and MRI.
Hormone Receptor Status
Breast cancer cells that have receptors for the hormone estrogen are called estrogen receptor (ER) positive, and those with receptors for progesterone are called progesterone receptor (PR) positive. If these receptors are not present, the cell is said to be hormone receptor negative.
Tumors that are hormone receptor positive are more likely to respond to therapy with antiestrogen medications, which take advantage of the cancer cell's dependence on hormones for growth. The drug tamoxifen, for example, acts by blocking the estrogen receptors of a breast cancer. Another class of drugs called aromatase inhibitors, used in postmenopausal women, interferes with the production of estrogen.
HER2/neu is a gene that, when activated, helps tumors grow by producing a specific growth-stimulating receptor. Tumors that have higher than normal amounts of this protein (HER2 positive) may respond to the drug trastuzumab (Herceptin®), which blocks the growth of tumors activated by the gene, or a similar drug called lapatinib (Tykerb®).
Triple-Negative Breast Cancer
About 10 to 15 percent of breast cancers do not contain receptors for estrogen, progesterone, or HER2/neu. They are called triple-negative breast cancers. They are particularly difficult to treat successfully because they do not respond to drugs such as tamoxifen, anastrozole, trastuzumab, and lapatinib. In addition, triple-negative breast cancers tend to be more aggressive, occur earlier in life, and pose a greater risk of recurrence than other types of breast cancer. Women with triple-negative breast cancer may be more likely to carry a BRCA mutation, especially if they are diagnosed at a young age. Memorial Sloan-Kettering researchers are studying the biology of triple-negative breast cancer to learn more about the disease and hopefully identify new therapeutic targets.
Grade is an evaluation of how abnormal or disorganized breast cancer cells appear when examined under a microscope. In general, a lower grade implies a less aggressive tumor.
Lymphovascular or Perineural Invasion
Sometimes tumor cells can invade the blood vessels or the lymph or nerve channels within breast tissue.
Oncotype DX® is a test that is used to analyze 21 genes in patients with a breast tumor that is estrogen receptor positive and has not spread into the axillary lymph nodes. Information is translated into what is called a recurrence score, which enables doctors to predict which women will benefit most from chemotherapy, and which women will not.
The Oncotype DX® test is part of a novel and increasingly popular approach called personalized medicine for cancer. As our knowledge of tumor biology improves, our researchers are seeking more precise molecular markers that can help predict how a patient will respond to a specific treatment.
Memorial Sloan-Kettering researchers have been evaluating the prognostic value of hormone receptors, cancer-related genes (called oncogenes), and certain enzymes produced by cancer cells that help the cells to spread. A particular focus is the role of genetic mutations (such as those in the BRCA1 and BRCA2 genes) in the development and progression of breast cancer and its responsiveness to treatment.
Our goal is to integrate these laboratory research findings into the care we offer our patients, customizing each individual's treatment based on the specific molecular signals driving the growth of a specific cancer.