Prognosis

In the U.S., about 40,460 women will die from breast cancer this year, making it the second most lethal cancer in women. (Lung cancer is the leading cancer killer in women.) The good news is that early detection and new treatments have improved survival rates. The 5-year survival rate for women diagnosed with cancer is 80%. About 88% of women diagnosed with breast cancer will survive at least 10 years. Unfortunately, women in lower social and economic groups still have significantly lower survival rates than women in higher groups.

Several factors are used to determine successful treatment and the possibility for a cure. They include:

• The location of the tumor and how far it has spread
• Whether the tumor is hormone receptor-positive or -negative
• Genetic factors
• Tumor size and shape
• Rate of cell division
• Biologic markers

The good news is that women are living longer with breast cancer, and at this time more than 2 million American women are survivors. Due to better treatment options, from 1990 - 2003, breast cancer mortality rates declined by 24%. However, survivors must live with the uncertainties of possible recurrent cancer and some risk for complications from the treatment itself.

Recurrences of cancer usually develop within 5 years of treatment. However, 25% of recurrences and half of new cancers in the opposite breast occur after 5 years. One study suggested that the risk factors for a first breast cancer do not necessarily place a woman at any higher risk for recurrence. (Women with a first cancer, however, do have a higher risk for a new cancer in the opposite breast. The outlook for such new cancers is independent from those of the first one.)

Location of the Tumor

The location of the tumor is a major factor in outlook:

• If the cancer is ductal carcinoma in situ (DCIS) or has not spread to the lymph nodes (is node-negative), the 5-year survival rates with treatment are up to 98%. However, cancer recurs in 9 - 30% of women with node-negative cancers. Recurrence is a potentially life-threatening problem, even if the disease relapses locally in the same breast. In one study of DCIS patients with locally invasive recurrence, 8-year mortality rates were only 12%.
• If the lymph nodes contain cancer cells (are node positive) then survival rates fall. If the tumor is larger than 5 cm or there is widespread involvement in the lymph nodes, the cancer is sometimes referred to as locally advanced. In such cases, the survival rate drops to about 75% and below.
• If the cancer has spread (metastasized) to other sites (most often the lung, liver, and bone), the average survival time is about 2 years (with some patients living for many years). New drug therapies, particularly aromatase inhibitors, have helped prolong survival for women with metastatic cancer.

The location of the tumor within the breast is an important predictor. Tumors that develop toward the outside of the breast tend to be less serious than those that occur more toward the middle of the breast.

Hormone Receptor-Positive or -Negative

Breast cancer cells may contain receptors, or binding sites, for the hormones estrogen and progesterone. Cells containing these binding sites are known as hormone receptor-positive cells. If cells lack these connectors, they are called hormone receptor-negative cells. About 75% of breast cancers are estrogen receptor-positive (ER-positive, or ER+). About 65% of ER-positive breast cancers are also progesterone receptor-positive (PR-positive, or PR+). Cells that have receptors for one of these hormones, or both of them, are considered hormone receptor-positive.

Hormone receptor-positive cancer is also called "hormone sensitive" because it responds to hormone therapy such as tamoxifen or aromatose inhibitors. Hormone receptor-negative tumors are referred to as "hormone insensitive" or "hormone resistant."

Women have a better prognosis if their tumors are hormone receptor-positive because these cells grow more slowly than receptor-negative cells. In addition, women with hormone receptor-positive cancer have more treatment options. (Hormone receptor-negative tumors can be treated only with chemotherapy.) A 2007 study in the Journal of Clinical Oncology indicated that recent declines in breast cancer mortality rates have been most significant among women with estrogen receptor-positive tumors, due in part to the widespread use of post-surgical tamoxifen therapy.

The Influence of Genes

Determining a "genetic signature" for a tumor may prove to be a very powerful predictor of the aggressive nature of a breast cancer. Researchers have focused on 70 genes whose activity patterns may help make such predictions. In 2007, the Food and Drug Administration approved MammaPrint, a DNA microarray diagnostic test that profiles these 70 genes. The molecular test may help predict how likely it is that breast cancer will recur within 5 - 10 years. However, the accuracy of the test depends on a woman’s risk. It is more accurate when predicting a low risk for recurrence than a high risk.

The relevance of the inherited BRCA1 or BRCA2 mutations to survival is controversial. Some studies have suggested that these mutations offer a survival advantage. Others suggest that they make no difference or even worsen prognosis. Women with these genetic mutations do have a greater risk for a new cancer to develop. Patients with BRCA1 mutations tend to develop tumors that are hormone receptor negative, which can behave more aggressively.

Tumor Markers

Researchers are investigating numerous substances in tumor cells that may indicate whether or not a cancer is likely to spread. Such chemical markers may help doctors determine treatments, and some may even prove to be targets for future drugs. The following are only a few of the more well-researched markers.

HER2. The American Cancer Society recommends that all women newly diagnosed with breast cancer get a biopsy test for a growth-promoting protein called HER2/neu. HER2-positive cancer usually occurs in younger women and is more quickly-growing and aggressive than other types of breast cancer. The HER2 marker is present in about 20% of cases of invasive breast cancer. Two types of tests are used to detect HER2:

• Immunohistochemistry (IHC)
• Fluorescence in-situ hybridization (FISH)

Some doctors think that FISH is a more accurate test than IHC. According to 2006 HER2 testing guidelines from the American Society of Clinical Oncology and the College of American Pathologists, either test may be used as long as it is performed by an accredited laboratory. Tests that are not clearly positive or negative should be repeated. Treatment with trastuzumab (Herceptin) or lapatinib (Tykerb) may help women who test positive for HER2.

Angiogenesis Factors. Angiogenesis is the growth of new blood vessels. High levels of angiogenesis factors indicate that the tumor is developing its own supply of blood vessels, which enable the tumor to send colonies of cancer cells into the bloodstream and spread to other parts of the body. Specific angiogenesis factors, such as vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF), may turn out to be important markers for determining treatment and prognosis. The monoclonal antibody bevacizumab (Avastin) targets VEGF. The drug is showing promise in clinical trials for prolonging progression-free survival in women with metastatic breast cancer.

Others. Many other markers are being investigated, including p53, cathepsin-D, protein c-erbB-2, bcl-2, Ki-67, telomerase, thymidylate synthase, CA 15-3, and carcinogenic embryonic antigen (CEA). The American Society of Clinical Oncology (ASCO) cautions, however, that the value of many of these factors has not yet been confirmed.

Other Factors for Predicting Outlook

Tumor Size and Shape. Large tumors pose a higher risk than small tumors. Undifferentiated tumors, which have indistinct margins, are more dangerous than those with well-defined margins.

Rate of Cell Division. The more rapidly a tumor grows, the more dangerous it is. Several tests measure aspects of cancer cell division and may eventually prove to predict the disease. For example, the mitotic index (MI) is a measurement of the rate at which cells divide. The higher the MI, the more aggressive the cancer. Another test measures cells at a certain phase of their division.

The Effects of Emotions and Psychological Support

Recent evidence has not supported early reports of survival benefits for women with metastatic breast cancer who engage in support groups. However, some studies have suggested that psychotherapy, group support, or both may relieve pain and reduce stress, particularly in women who are suffering emotionally. Stress has been ruled out as a risk factor either for breast cancer itself or for its recurrence.