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How Breast Cancer Spreads

Early Detection and Improved Treatments Help Increase Survival Rates

By Maureen Salamon

Updated August 18, 2008

(LifeWire) - Breast cancer is frightening enough without the fear that it could travel to other parts of the body. Metastasis is the term for the spread of cancer.

About 240,000 women are diagnosed with breast cancer each year. Metastasis significantly lessens the likelihood of a cure, but for most breast cancer patients it remains a threat rather than a reality.

Improved Prospects for Breast Cancer Patients

Fortunately, for many, the risk of metastasis is relatively low, but early diagnosis is key.

About 20% of women are diagnosed at the very earliest stage (before the cancer has moved beyond a breast duct or ducts to invade surrounding breast tissue). Another 70% learn of their cancer while it's still contained within the breast or draining lymph nodes. Both groups have good prospects of avoiding metastasis altogether.

Only 10% are diagnosed after the cancer has already progressed to distant areas, which for breast malignancies typically includes the bones, lungs, liver or brain.

Encouragingly, however, nearly 90% of women who have had breast cancer will be alive 5 years after diagnosis, 81% after 10 years and 73% after 15 years, according to the American Cancer Society.

Metastasis: Fear and Understanding

Mary Jane Massie, M.D., a psychiatrist who specializes in breast cancer care at Memorial Sloan-Kettering Cancer Center in New York City, says that fear of metastasis is widespread among her patients, but it usually isn't emotionally crippling.

"We sure don't want people consumed by the idea and would want them to seek psychological health care if they were," Massie says. "But do most become incapacitated by the fear that (the cancer) will happen again? No."

However, as part of their self-care, women would be well advised to understand how breast cancer can spread. When diagnosed, each patient's cancer is classified by stage, with stage 0 being an early form and stage IV indicating spread to distant sites. Patients can use this information to manage their expectations.

How Breast Cancer Spreads

Breast cancer spreads in three different ways -- through the lymph system, which is the most common; through the blood; or through tissue, as when a tumor grows into, or invades, surrounding normal cells. If another tumor forms elsewhere in the body through metastasis, it's the same kind of cancer as the original tumor. A new tumor in the lung, for instance, is considered metastatic breast cancer, not lung cancer. However, these metastasized tumors tend to be more aggressive than the original breast tumor.

Whether breast cancer will eventually spread depends a great deal on the aggressiveness of the type of tumor with which a woman is initially diagnosed. The earlier the stage at diagnosis, the less likely the cancer has already metastasized.

For women whose cancer is detected while still confined to the breast -- before any lymph node involvement -- the risk of eventual metastasis is only 5% to 10%. The odds of recurrence increase greatly for cancer diagnosed at more advanced stages, with estimates of metastasis ranging from 30% to 85%.

Metastatic cancer typically develops (if at all) within 3 years of the initial cancer treatment, often invading lymph nodes near the breast -- located in the armpit and chest wall -- before traveling to farther sites. But again, much depends on the grade and aggressiveness of each individual tumor, with some carrying much higher recurrence rates. About a quarter of all metastases first appear in the bones. The lungs (at about 20%), liver and brain (the latter two accounting for about 15% each) are next most common sites for cancer spread.

"If the cancer is localized in one or two lymph nodes, there's a pretty low risk" of spread, says Debbie Saslow, Ph.D., director of breast and gynecologic cancer for the American Cancer Society. "If it's a particularly large tumor or involves lots of nodes, the risk definitely increases."

Symptoms of Metastasis

Metastasis may cause symptoms in the area where the cancer has newly appeared. Bone metastases (the most common type) can produce bone pain; lung metastases can produce coughing or shortness of breath; and liver metastases can produce depressed appetite and weight loss. A brain metastasis may cause neurological symptoms, such as headaches, blurry vision or a feeling of weakness.

"A lot of women get anxious about any ache or pain they experience for even years after [initial breast cancer] treatment," Saslow says. "But most metastases would occur before there are any symptoms."

Diagnosing and Treating Metastatic Breast Cancer

Doctors have several ways of determining whether the cancer has spread or not. These involve imaging the body, using x-rays, bone scanning, MRIs or CT scans. Blood tests can check levels of certain chemicals in the blood, including specific tumor markers associated with metastasis.

In addition, physicians often rely on biopsies, which are tissue samples gathered by surgical removal or needle extraction. These samples are then examined under a microscope for cellular abnormalities that indicate whether there is progression of the cancer.

Treatment for metastatic breast cancer, which focuses on symptom management and disease control, depends on the type and aggressiveness of the tumors. Treatment may include chemotherapy, radiation, surgery or hormone medications. Biologic therapy, which encompasses any treatment aimed at the specific biology or makeup of tumor cells, may also be used.

The median survival time for women with stage IV breast cancer -- that is, cancer that has metastasized -- is 18 to 24 months. But some tumors can be controlled for much longer -- sometimes in excess of 20 years. Breast cancer patients should consult their personal physicians regarding the outlook for their specific type of cancer.

Sources:

"Breast Cancer Facts & Figures 2007-2008." American Cancer Society. Atlanta: American Cancer Society Inc. 13 Jul. 2008.

"Breast Cancer Metastasis in Women." cancer.med. July 2006. University of Michigan. 13 Jul. 2008.

Massie, M.D., Mary Jane. Telephone interview. 14 Jul. 2008.

Nakagawa, T., S.R. Martinez, Y. Goto, K. Koyanagi, M. Kitago, T. Shingai, D.A. Elashoff, X. Ye, F.R. Singer, A.E. Giuliano and D.S.B. Hoon. "Detection of Circulating Tumor Cells in Early-Stage Breast Cancer Metastasis to Axillary Lymph Nodes." Clinical Cancer Research 13(2007): 4105-10.

Saslow, Ph.D., Debbie. Telephone interview. 3 Jul. 2008.

"Stages of Breast Cancer." cancer.gov. 13 Jun. 2008. National Cancer Institute. 13 Jul. 2008.

LifeWire, a part of The New York Times Company, provides original and syndicated online lifestyle content. Maureen Salamon is a New Jersey-based freelance writer who has written for newspapers, websites and hospitals.
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