Breast cancer is 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. 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 the risk for recurrence and the likelihood of successful treatment. They include:
- Location of the tumor and how far it has spread
- Whether the tumor is hormone receptor-positive or -negative
- Tumor markers
- Gene expression
- Tumor size and shape
- Rate of cell division
Women are now living longer with breast cancer. Breast cancer mortality rates have declined by about 25% since 1990. This decline may be due to better screening and better treatment options. 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. About 25% of recurrences and half of new cancers in the opposite breast occur after 5 years.
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 (node negative), the 5-year survival rates with treatment are up to 98%.
- If the cancer has spread to the lymph nodes or beyond the primary tumor site (node positive), the 5-year survival rate is about 84%.
- If the cancer has spread (metastasized) to other sites (most often the lung, liver, and bone), the average 5-year survival rate is 23%. New drug therapies, particularly aromatase inhibitors, have helped prolong survival for women with metastatic (stage IV) 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 aromatase 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.) 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 hormone-blocking therapy.
Review Date: 11/08/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.