Local, Regional, and Distant (Metastatic) Spread of Cancer

Metastatic cancer is a cancer that has spread from its primary site (the part of the body in which it developed) to other parts of the body. If cells break away from a cancerous tumor, they can travel to other areas of the body. There, they may settle and form "colony" tumors. In their new location, the cancer cells continue growing. The spread of a tumor to a new part of the body is called metastasis.

It is important to understand the difference between metastasis and local spread, because they affect a patient's prognosis (the outlook for chances of survival) and treatment options in different ways.

Local spread means that a growing cancer extends beyond the organ in which it developed, into nearby organs and tissues. For example, the cervix (lower part of the uterus or womb) is located in front of the rectum and behind the bladder. Very large cancers of the cervix may extend into the rectum or bladder.

Metastasis involves spread of cancer cells through the bloodstream, or the lymph system. The lymph system consists of lymph vessels (similar to veins except that they contain tissue waste products and immune system cells instead of blood). These lymph vessels lead to lymph nodes, bean-shaped collections of immune system cells that are important in fighting infections. Cancer cells that break off from tumors and enter the lymph vessels may be carried to lymph nodes where they may continue to grow and form metastases. Doctors sometimes call metastasis to lymph nodes near the place a cancer developed regional spread. This is to distinguish it from distant spread or distant metastasis. Distant spread generally occurs when cancer cells break off from tumors and enter the bloodstream, travel to other organs, and continue to grow into new tumors.

When cancer spreads, it is still named after the part of the body where it started. For example, if prostate cancer spreads to the bones, it is still called prostate cancer, and if breast cancer spreads to the lungs it is still breast cancer.

Recurrence and Metastasis

Recurrence is the medical term used when cancer comes back in a patient who appeared to be in remission (free of cancer) after treatment. Cancer can recur locally, in the same organ it developed in or, if that organ was removed by surgery, in a nearby remaining organ or tissue. For example, local recurrence of breast cancer means cancer started to grow again in the same breast after lumpectomy and radiation therapy or in the chest wall, skin or muscle after a mastectomy. A regional recurrence usually means cancer has come back in nearby lymph nodes or in the area that lymph nodes had been removed from. After apparently complete removal of a mouth or throat cancer, growth of cancer in lymph nodes of the neck would be considered regional recurrence. A distant recurrence involves any other part of the body not included in local or regional recurrence. After surgery for apparently localized prostate cancer, the cancer might recur distantly in bones, the liver, or the lungs.

But, recurrence is not the only time a cancer will metastasize. Some cancers are discovered to have spread to nearby lymph nodes or distant organs shortly after the cancer is first diagnosed, and before treatment is started. In some cases, a metastasis may be discovered before the primary (original) tumor is found. For example, a patient may go to the doctor because lymph nodes in the neck are growing larger. After a biopsy reveals cancer in these lymph nodes, additional examinations or x-rays may find that the cancer actually started in the throat. Even if a cancer has spread very widely throughout the body before it is discovered, the cancer's appearance under a microscope can sometimes tell doctors where it started. But, some cancers lack these microscopic clues to their origin, and it may be impossible to determine exactly where they started. This condition is called cancer of unknown primary, and is discussed further in a separate American Cancer Society document.

So, cancer can recur without metastasizing (a local recurrence) and can metastasize without recurring locally (cancer found to have metastasized when first diagnosed).

Significance of Metastasis to the Patient

Most people who die of cancer have metastases at the time of their death. And, these metastases are directly responsible for the majority of cancer deaths. Most common cancers (prostate, breast, colon, lung, for example) develop in organs that can be completely or partially removed by surgery. Even though these operations cause effects, they could cure patients if metastasis did not occur. Most of the serious consequences of these cancers occur because of spread to other parts of the body. In some cases, the most serious effect of cancer is its spread to a particularly essential part of the body, such as areas of the brain. In other cases, spread to and growth in many organs creates so many cancer cells that the body's normal metabolism is disrupted.

However, cancer can be fatal even if it does not metastasize. Cancers that start in the brain may be impossible to remove without causing severe brain damage. In fact, brain tumors rarely spread beyond the nervous system. Growth and local spread of these cancers often interfere with parts of the brain necessary for life. A tumor may become very large without ever metastasizing. It may then press against vital tissues such as nerves, the brain, or blood vessels. Leukemia can cause death by interfering with normal blood functions without the defective cells ever leaving the tissues they started in (the bone marrow and bloodstream).