One of the things that makes cancer so deadly is that it has the ability to spread throughout the body without warning. Cancer cells can spread by moving into nearby normal tissues and muscles and spread regionally to lymph nodes and organs. It can also travel the length of the body beginning in the chest and developing in the calves and thighs. When this type of spreading throughout the body occurs, it is called metastatic cancer, or stage four cancer. The process that allows this to happen is metastasis.
When metastatic cancer cells are examined under a microscope, it can be seen if they are part of the original cancer, part of the spreading, or the cells that are created by the areas of tissue infected with cancer. This test allows doctors to determine which areas the cancer has metastasized in, or if they are just the remnants of the cancer cell production.
Metastatic cancers take on the same name as their primary cancer counterparts. Breast cancer that spreads into the stomach is called metastatic breast cancer, and not stomach cancer. Lung cancer that spreads to the brain is metastatic lung cancer, not brain cancer. Often when metastatic cancer is diagnosed the doctors may not be able to tell where the cancer began. This type of cancer is called cancer of unknown origin, or CUP. When a new cancer is diagnosed as primary in any person with a history of cancer, this is known as secondary cancer. Secondary cancers are rare, and many times when cancer is found again, it simply means the original type has returned.
How does cancer spread?
Cancer cells spread through the body in a multitude of ways. Usually, the steps the cells take to have regrowth are as follows:
- First, the cells grow into or invade any nearby normal tissues.
- Second, the cells begin to move through the walls of nearby lymph nodes or blood vessels.
- Next, they begin traveling through the lymphatic system and bloodstream to other parts of the body.
- Then the cells stop in the small blood vessels at distant locations, invading those blood vessel walls and moving further into the surrounding tissues.
- Next, the overgrowth of cells begins to form tiny tumors.
- Finally, around these new tumors, blood vessels begin to heal or regrow, which reestablishes a constant blood flow to the tumor, which increases its growth and size.
In some cases, the newly formed cancer cells spread, and then die off at different points of the cycle. If conditions are favorable at two or more phases of this cycle, the cancer can continue to spread, growth and evolve into other forms of cancer. Metastatic cancer cells can also stay inactive at a distant site for years before growing again or beginning to grow somewhere else in the body.
Where will the cancer spread?
Most cancers have the potential to spread to any part of the body. Certain types of cancer are more likely to spread than others, and into more common areas of the body where metastasizing is easier for the body. The most common sites for spreading are the bone, lungs and liver. The following chart shows the most common sites for metastasis, excluding the lymph nodes.
| Cancer Type | Main Sites of Metastasis |
| Bladder | Bone, liver, lung |
| Breast | Bone, brain, liver, lung |
| Colon | Liver, lung, peritoneum |
| Kidney | Adrenal gland, bone, brain, liver, lung |
| Lung | Adrenal gland, bone, brain, liver, other lobes in the lung |
| Melanoma | Bone, brain, liver, lung, skin, muscle |
| Ovary | Liver, lung, peritoneum |
| Pancreas | Liver, lung, peritoneum |
| Prostate | Adrenal gland, bone, liver, lung |
| Rectal | Liver, lung, peritoneum |
| Stomach | Liver, lung, peritoneum |
| Thyroid | Bone, liver, lung |
| Uterus | Bone, liver, lung, peritoneum, vagina |
What are the symptoms of metastatic cancers?
The symptoms of metastatic cancers do not always show themselves. In some cases, people have metastatic cancer for months before they finally find out what is happening inside of them. If symptoms do present, the degree and frequency will depend on the cancers’ location and size. There are a few common signs of metastatic cancer, and they are:
- Pain and fractures, when cancer has spread to the bone
- Headache, seizures, or dizziness, when cancer has spread to the brain
- Shortness of breath, when cancer has spread to the lung
- Jaundice or swelling in the belly, when cancer has spread to the liver
What is the treatment plan for metastatic cancers?
Once cancer begins to spread, it is much harder to control. While some metastatic cancer can be cured with treatments like chemotherapy or radiation, most cannot be treated at all. There are still certain treatments used for metastatic cancer with goals of slowing the growth, the spread, and relieving the symptoms caused by the cancer. In some cases, the treatment can also help prolong life and slow the overall progression inside of the body.
The treatments do vary based on the type of primary cancer that you have, where it is located, where it has spread, and all of the treatments you have had in the past. Your general health is also taken into account, as an unhealthy body cannot usually tolerate the heavy medications and stress that comes with these treatments.
What does it mean when my doctor tells me that my metastatic cancer is uncontrolled?
If your doctor has told you this, this means that your cancer can no longer be controlled by any currently known method of treatment, and you should begin preparing yourself and your loved ones for your end-of-life care and planning. Even if you choose to try a treatment and continue trying to control the cancer, palliative care to control the symptoms and side effects can absolutely begin.
If you have further questions about metastatic cancer, or if you are at a greater risk for this type of cancer, schedule a meeting with your medical care team to discuss and plan. Empowering yourself with education and knowledge will help you remain as calm as possible, which will also help control your cancer and heal.
Citations:
American Cancer Society
WebMD
Centers for Disease Control and Prevention
Journal of the National Cancer Institute