How cancer spreads and what we are doing about it

When a patient receives a diagnosis of cancer, fear, disbelief, concern, anxiety and sometimes anger are the emotions often felt. In great part, these very justified emotions are due to the notorious fashion in which cancer can cause human suffering.  One ways it does so is by spreading to other parts of the body and causing those parts of the body to malfunction.  This process of a cancer spreading, called metastases, is one central difference between a normal cell and a cancer cell. Cancer cells can spread or metastasize to other portions of the body, while normal cells stay put, in the organ in which they normally reside. The spread of a successfully treated cancer is a development many patients fear most.  After a series of treatments with chemotherapy, surgery, or radiation treatments, a cancer may return at a different place, months or years later. Until recently, very little attention was paid to the process whereby these cancer cells were able to spread, but now, there is great excitement about the process, as researchers begin to understand how these cells cause harm.

THE MANY DIFFERENT STEPS INVOLVED IN CANCER SPREAD

The process by which cancer cells spread, once a mystery, is being unraveled. And it is this understanding that has us excited. The cancer cell that is able to spread is remarkable for a number of reasons. In fact, in most types of cancer, only a small number of cancer cells are able to spread.   Just think of all it has to do. To do be able to spread, a cancer cell must:

• leave or break off from the organ from which it developed
• navigate through the surrounding tissues
• attach itself to the outside of a blood vessel
• figure a way to get into the blood vessel
• figure out a way to travel throughout the blood vessel
• attach itself to the inside of that blood vessel
• have the ability to get out of the blood vessel that it was traveling in.
• determine the best place to land (such as liver or bone)
• create a new set of its own blood vessels in the new place of residence
• divide again and again, as it becomes a new tumor lump far away from where it developed.

The journey that the cancer cells embark upon has many steps or sets of instructions -- like the many directions that we would need if we were traveling by car from Boston to Los Angeles. We would need a detailed set of instructions to prevent us from getting lost.  Likewise, the cancer cell that goes (or spreads) from one place to another also possesses a set of complicated instructions – in its genetic material or its DNA. 

WHY THE EXCITEMENT

We now have a much better understanding of each of the steps that allow a cancer cell to spread. And with this understanding comes the real hope and promise to do something that will interfere with the cells’ journey. For example, if we understand the chemical reactions and the chemicals that a cancer cell makes in order for it to invade a blood vessel, we could develop a specific drug to block the attachment of the cell to the outside of a blood vessel, thus preventing it from getting into the blood vessel in the first place. Similarly, if we could stop the progress of a cancer cell from navigating its way through its surrounding tissues, we could possibly stop the process of metastases from occurring altogether. Then, surgery or radiation treatment of the tissue where the cancer originated from would have a much better chance of success in eradicating the entire cancer. Even better, we could also develop a drug that could be taken to prevent the metastatic process altogether.

Just recently, researchers have been successful in identifying the genes or DNA that are involved in a cancer cell’s ability to make new blood vessels that carry nutrients, a process vitally important for a cancer’s survival.  This knowledge could lead to the development of “designer drugs” that can specifically block or detour the cancer’s journey from one place in the body to another.  It is realistic to envision that at some point in the not-too-distant future, cancer treatments will include, in addition to well-established anti-cancer drugs that shrink or eradicate cancers, new drugs that also prevent the spread of cancer.

Let me know if you have questions about why or how cancers spread.

Marc Garnick, M.D., is an internationally renowned expert in medical oncology and urologic cancer, with a special emphasis on prostate cancer. He is a Clinical Professor of Medicine at Harvard Medical School and maintains an active oncology practice at Beth Israel Deaconess Medical Center. Dr. Garnick serves as Editor in Chief of Perspectives on Prostate Diseases, a quarterly report from Harvard Health Publications.

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