FEB 29, 2024 3:00 AM PST

What is Metastatic Cancer?

WRITTEN BY: Katie Kokolus

We focus on a lot of studies investigating metastatic cancer, a disease that occurs when cancer cells spread from their original anatomical location to a distant part of the body.  So, let’s take a closer look at metastatic cancer.

First, let’s explore some terminology.  When cancer spreads, or metastasizes, from its origin site to a different organ, the newly developed cancer, or metastasis, typically has many of the same features and characteristics of the original malignancy.  This means, for example, that colorectal cancer that spreads to the liver will look like colon cancer cells, not liver cancer cells.  In this case, the legions in the liver may be referred to as liver metastases, and the patient may be diagnosed with metastatic colorectal cancer.  In addition, you may hear the colon malignancy referred to as the” primary cancer” and the colon referred to as the “primary site.”  Here, the liver becomes the “secondary site,” and the disease might be called “secondary liver cancer.”  For many cancers, metastatic cancer may also be referred to as “Stage IV.”  In rare cases, doctors may not be able to identify where metastatic cancer originated.  In this circumstance, the disease would be designated as “cancer of unknown primary” (CUP). 

Next, let’s talk about how metastasis occurs.  Metastatic spread, like cancer growth, is a very complex biological process made up of several steps.  One method for metastasis occurs when cancer cells grow directly into nearby tissue.  However, cancer cells can also enter the blood and travel to more distant areas of the body.  Similarly, cancer cells can travel through the lymph system , which consists of various tissues and organs that produce, store, and transport immune cells throughout the body.  The lymph system contains lymph nodes and lymphatic vessels that carry immune cells, and in the case of metastatic spread cancer cells, to various anatomical sites.   Once cancer cells arrive at a new location, regardless of the distance they have traveled, the cells have to grow into the new tissue.  After the secondary tumor forms, new blood vessels will begin to grow to provide nutrients to the growing metastasis. 

Now, let’s look at where cancer can spread.  In theory, cancer cells can spread just about anywhere in the body.  However, some secondary cancers occur more commonly than others, and the brain, bone, liver, and lung represent the more prevalent metastatic regions.  Further, each primary cancer is associated with its own common metastatic locations.  To stick with our original example, colon cancer mostly commonly metastasizes to the liver, lung, or peritoneum. 

Finally, we should talk about metastatic cancer treatment.  Not surprisingly, treatments will vary based on many factors, including the degree of spread and the metastatic site.  In some cases, surgical excision can eliminate all or most of the metastatic cancer, but systemic therapies, like chemotherapy or immunotherapy, could also alleviate secondary cancer in some locations. 

An estimated 90% of cancer-related deaths occur because of metastasis presenting, a critical need to focus research on new treatments and therapeutics that prevent metastatic spread. 


Sources: Cell, Cell Sys, Crit Rev Oncog

About the Author
Doctorate (PhD)
I received a PhD in Tumor Immunology from SUNY Buffalo and BS and MS degrees from Duquesne University. I also completed a postdoc fellowship at the Penn State College of Medicine. I am interested in developing novel strategies to improve the efficacy of immunotherapies used to extend cancer survivorship.
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