Disease Progression

We cannot say with certainty what causes prostate cancer. As I discussed in a prior post, we know that age is a significant risk factor, and that certain groups of people are more likely to get prostate cancer. The American Cancer Society has a comprehensive article on prostate cancer, and they say that it is suspected to start with small changes in prostate gland cells and grow from there. They also mention that certain inherited genes can increase risk. Other risk factors like smoking and having prostate inflammation are believed to contribute to risk.

Prostate cancer will start out in the prostate itself. According to the American Cancer Society, the next place it will spread is nearby tissue and lymph nodes. Here is a picture of the lymph nodes close to the prostate gland (in green).

Once the cancer enters the lymph nodes, it can spread through the lymphatic system to other parts of the body, and most commonly will go first to the bones. This picture gives you a general idea of what the lymphatic system looks like (in green). The green circles are lymph nodes (they are everywhere!), and the green lines are the pathways that lymph (the fluid that moves around in this system) travels through to reach lymph nodes. Looking at this picture, you can see how cancer cells near the prostate gland could hitchhike and spread to anywhere in the body.

Prostate cancer especially likes to spread to the spine, ribs, skull, and the top ends of the bones of your arms and legs. As you might remember from one of my first posts, cancer that has spread this far in the body is called Stage 4 (the most advanced stage). This stage of cancer is the most deadly.

Note: I have just briefly explained how prostate cancer can spread to its most deadly stage. However, in most men, prostate cancer grows very slowly. Most men with prostate cancer will not die from it, because it is so slow growing that it will remain within the prostate gland, not causing much harm or spreading to other sites of the body. Some people have more aggressive (fast-growing and spreading) prostate cancer than others, which is more dangerous, but there is no sure way to tell what a person's outcome will be with certainty. 

You might ask, "so I know that cancer is bad, and that if it spreads this is bad, but I don't fully understand why. How exactly can it kill someone?" Here is a bit more information on how cancer takes over the body:

In the words of Cancer Research UK, cancers (like prostate cancer) can take over parts of the body that we need in order to survive. Cancer cells destroy the once normal tissues they invade so that they can no longer do what they were made to do. For example, if a cancer (like prostate cancer) moves to the lungs, a person's lungs will not be able to take in oxygen, which we need in order to survive. Also, our bodies are very complex and when they are healthy, they maintain a tightly controlled balance of chemicals and nutrients. Changes in one area of the body will affect other areas as well. Our bodies house complex, interconnected systems that depend on each other. So, for example, if we have cancer in our bones, our bones will become damaged and release Calcium into our blood. Bones store calcium, which is needed for survival, but healthy bones only release their calcium when we need them to. In cancerous bone, it is damaged and releases its calcium as a result, more than we need. When this keeps happening, over time it is too much for our bodies to handle and it can cause death. Other cancers can make substances that harm the body.

Sources:

The American Cancer Society (2015). "Prostate Cancer Overview." Retrieved from http://www.cancer.org/acs/groups/cid/documents/webcontent/003072-pdf.pdf

Cancer Research UK (2014). "How can cancer kill you?" Retrieved from http://www.cancerresearchuk.org/about-cancer/cancers-in-general/cancer-questions/how-can-cancer-kill-you