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All About Metastatic Cancer
By peace | December 11, 2006
Metastases spread in three ways - by local extension from the tumor to the surrounding tissues, through the bloodstream to distant sites or through the lymphatic system to neighboring or distant lymph nodes. Each kind of cancer may have a typical route of spread.
Metastasis means the spread of cancer. Cancer cells can break away from a primary tumor and enter the bloodstream or lymphatic system (the system that produces, stores, and carries the cells that fight infections). That is how cancer cells spread to other parts of the body.
When cancer cells spread and form a new tumor in a different organ, the new tumor is a metastatic tumor. The cells in the metastatic tumor come from the original tumor. This means, for example, that if breast cancer spreads to the lungs, the metastatic tumor in the lung is made up of cancerous breast cells (not lung cells). In this case, the disease in the lungs is metastatic breast cancer (not lung cancer). Under a microscope, metastatic breast cancer cells generally look the same as the cancer cells in the breast.
To determine whether a tumor is primary or metastatic, a pathologist examines a sample of the tumor under a microscope. In general, cancer cells look like abnormal versions of cells in the tissue where the cancer began. Using specialized diagnostic tests, a pathologist is often able to tell where the cancer cells came from. Markers or antigens found in or on the cancer cells can indicate the primary site of the cancer.
Metastatic cancers may be found before or at the same time as the primary tumor, or months or years later. When a new tumor is found in a patient who has been treated for cancer in the past, it is more often a metastasis than another primary tumor.
Symptoms Of Metastatic Cancer
Some people with metastatic cancer do not have symptoms. Their metastases are found by x-rays and other tests performed for other reasons.
When symptoms of metastatic cancer occur, the type and frequency of the symptoms will depend on the size and location of the metastasis. For example, cancer that spreads to the bones is likely to cause pain and can lead to bone fractures. Cancer that spreads to the brain can cause a variety of symptoms, including headaches, seizures, and unsteadiness. Shortness of breath may be a sign of lung involvement. Abdominal swelling or jaundice (yellowing of the skin) can indicate that cancer has spread to the liver.
Sometimes a person’s primary cancer is discovered only after the metastatic tumor causes symptoms. For example, a man whose prostate cancer has spread to the bones in his pelvis may have lower back pain (caused by the cancer in his bones) before he experiences any symptoms from the primary tumor in his prostate.
Which Cancers Spread Where?
Cancer cells may travel from the place they started through the blood or lymphatic system to other parts of the body. The type of cancer and where it starts often have an effect on where it will spread. Breast cancer, for example, often spreads first to lymph nodes under the arm because this is where the lymph fluid drains first. It rarely spreads to lymph nodes farther away in the groin. Likewise, the lung is a common place for cancer to spread. This is because the heart pumps blood from the rest of the body through the lung’s blood vessels before sending it elsewhere. The liver is a common site for spread of cancer cells from the stomach and intestines because blood from these organs flows into the liver.
Sometimes, though, the pattern of spread cannot be explained by anatomy. It seems to be caused by the certain cancer cells being able to “home in” on certain places in the body.
Bladder: Bladder cancer tends to invade nearby tissues such as the pelvic wall. It also spreads to lungs, liver, and bone.
Brain: Brain cancer rarely spreads outside the brain.
Breast: Breast cancer most often spreads to bone but can also spread to the liver, lung, and brain. As the cancer grows, it may affect any organ, even the eye. It can also spread to the skin near where it started.
Colorectal: The most common place for colon cancer to spread is the liver. Next are bone and lung. Rectal cancer can spread into the pelvis and also to the lung, brain, and bone.
Esophagus: Esophageal cancer grows mostly nearby. As it grows, it may slowly become hard for the patient to swallow.
Kidney: Kidney (renal) cancer can invade directly into nearby tissues. It spreads most often to the lungs and bones.
Leukemia: Leukemia can fill the bone marrow with cancer cells. As the bone marrow is replaced, it can no longer make normal blood cells.
Liver: Liver cancer doesn’t often spread outside the liver. Rather it spreads within the liver.
Lung: Lung cancer can spread to any organ of the body, but most often it will spread to the liver, bones, and brain. It can also grow into the sac around the heart.
Lymphoma: Lymphoma tends to stay in the lymph nodes and bone marrow. It will spread to other organs when it is very far advanced.
Melanoma: Melanoma can spread anywhere in the body. It first tends to spread to nearby lymph nodes but can then spread through the blood to the brain, lungs, liver, and bone.
Mouth and throat: Cancers of the mouth, throat, or nose tend to grow nearby. When they spread, it is often to the lungs.
Multiple myeloma: Multiple myeloma mainly stays in the bone where it started. It rarely spreads elsewhere. But myeloma can cause the bones to weaken and break. As it dissolves bone calcium is released into the blood. Myeloma also makes a protein that can damage the kidneys.
Ovary: Advanced ovarian cancer most often spreads to the lining and organs of the abdomen. This can cause a build-up of fluid and swelling. It can also spread to the outer lining of the lung and cause fluid there to build up. Much less often it spreads outside the abdomen and pelvis.
Pancreas: Pancreatic cancer mainly stays in the abdomen and grows locally as well as spreading to the liver. It can also spread to the lungs, bones, and brain.
Prostate: Prostate cancer usually goes to the bones when it spreads. Much less often it will spread to other organs, including the brain.
Stomach: Stomach cancer tends to spread nearby and within the abdomen. The next areas it usually goes to are the liver and lungs. Spread to the bone and brain is less common.
Treatment Of Metastatic Cancer
Treatment options for people with metastatic cancer will depend on where the cancer started and where it has spread to. Other factors will also be considered, such as specific features of the cancer cells (in the case of breast cancer, whether they contain estrogen receptors), the patient’s general state of health, and which treatments that patient has already received.
As a general rule, localized cancers are most effectively treated with surgery or radiation therapy, and metastatic cancers are treated with systemic therapies, such as chemotherapy or hormonal therapy. Systemic therapies are taken by mouth or injected. They enter the bloodstream, and can therefore reach cancer cells that have spread throughout the body.
