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

Who has prostate cancer? What are the trends?

This week I am going to talk about a big fancy word called the "epidemiology" of prostate cancer in the US. This just means I am going to look at where prostate cancer is and which groups of people are most likely to have it. I am using the National Cancer Institute's website primarily as my source of information as well as the CDC.

How many men get it? How many die from it each year?

Prostate cancer is one of the most common cancers among men, and 1 in 7 will be diagnosed with it (hence the title of my blog, "1 in 7"). However, if caught early, prostate cancer has high treatment success (Cancer Treatment Centers of America 2015).

According to the National Cancer Institute, last year (2014) there were around 233,000 new cases of prostate cancer reported (note how I say reported. There still might be many more people with it who have not been diagnosed or who were missed/not accounted for in the statistics). There were 29,480 estimated deaths from prostate cancer. Additionally, if we look at trends over time (the latest data availble for trends is from 1992-2011), we see that new prostate cancer diagnoses are going down, and the amount of deaths from it are lower than the amount of people newly found to have it.

National Cancer Institute. SEER Fact Sheets: Prostate Cancer:"At a Glance." Retrieved from http://seer.cancer.gov/statfacts/html/prost.html

Prostate cancer is slow-growing and men with it will often not die from it. They will often die from another cause instead of prostate cancer. Thus, there are high numbers of new cases but much fewer deaths from it. It often does not spread to other parts of the body, but when it does, we see higher  mortality rates. Here is a graph that shows the percentage of people who are expected to still be alive 5 years after their stage of diagnosis (it does not mean they are expected to live only 5 years):

National Cancer Institute. SEER Fact Sheets: Prostate Cancer:"Survival By Stage." Retrieved from http://seer.cancer.gov/statfacts/html/prost.html

How old are most people who have it?

Prostate cancer is a cancer of men, and risk increases with age. Most of the new diagnoses are made in men ages 65-75. Here is some food for thought about reporting diagnoses: people can only be diagnosed if they are screened for prostate cancer in the first place, so there might be more men with prostate cancer than we are aware of because they have not been screened.

National Cancer Institute. SEER Fact Sheets: Prostate Cancer: "Who Gets This Cancer?" Retrieved from http://seer.cancer.gov/statfacts/html/prost.html

Who is at the highest risk?

Also according to the national cancer institute, African American men as well as men whose fathers have or had prostate cancer are at the greatest risk (family history plays a role). Here is a graph that looks at risk by race. It looks at the number of newly diagnosed people per every 100,000 in the population. So, for example, if we look at men of Asian/Pacific Island descent in the United States, for every 100,000 of this subpopulation, 79.3 will be newly diagnosed with prostate cancer each year. They got this data from compiling data from 2007-2011.

National Cancer Institute. SEER Fact Sheets: Prostate Cancer: "Who Gets This Cancer?" Retrieved from http://seer.cancer.gov/statfacts/html/prost.html

What does the distribution look like in the United States?

This graph by the CDC looks at the percentage range of men who were newly diagnosed with prostate cancer in each state in 2011 (the most recent state-comparing data I found)

The Centers for Disease Control and Prevention. 2011. Rates of Getting Prostate Cancer By State. Retrieved from http://www.cdc.gov/cancer/prostate/statistics/state.htm.

What are some of the burdens of prostate cancer?

Economic: Cancer treatment is expensive, and prostate cancer treatment is no exception. Costs involved include screening, treatment, follow-up doctor's appointments, possible hospitalization, medication, etc. I am going to try and find more recent data than this, but am having difficulty. So for now, according to Pfizer (2005), the average yearly health care spending per person with prostate cancer (directly related to the prostate cancer) was about $3500 and the cost of comorbidities was about $8500 (Pfizer 2005). I feel like this cost would be higher than this today, however, so I will update this when I find better information. The total cost in the US for prostate cancer and comorbidity spending was nearly $13 billion.

Personal: If a person decides to undergo treatment, there will be costs involved besides the treatment itself and consultations such as transportation, a person might have to take time off of work depending on their specific situation, or the treatment of other problems that may arise such as depression or pain can cost money as well.

Emotional: Anyone diagnosed with a chronic disease will likely be at a greater risk for depression or grief. There may be adjustments in their lives emotionally, physically, and within their family and friendships.

Sources:

Cancer Treatment Centers of America (2015). "Prostate Cancer Information." Retrieved from http://www.cancercenter.com/prostate-cancer/learning/.

Centers for Disease and Control Prevention (2014). "Prostate cancer rates by state." Retrieved from http://www.cdc.gov/cancer/prostate/statistics/state.htm.

The National Cancer Institute Surveillance, Epidemiology, and End Results Program."Seer Stat Fact Sheets: Prostate Cancer." Retrieved from http://seer.cancer.gov/statfacts/html/prost.html

Prostate Cancer: What is it? What are its stages?

Prostate cancer is a cancer that starts in the prostate gland. To briefly explain its role, the prostate gland (which men have) helps with male sexual function. It makes a fluid that mixes with sperm to help produce semen during ejaculation. Here is a picture of where the prostate is (in this picture it is in the center of the black circle):

Prostate cancer is when the DNA of prostate gland cells mutates and no longer functions normally. Here are its stages according to TNM staging:

I: The cancer is in the prostate only (the tissue from which it came)

II: The cancer is more advanced, but has not quite spread outside of the prostate. We say it is still "encapsulated," or contained within the "capsule"/outer margins or borders of the prostate.

III. The cancer has spread beyond the outer layers/capsule of the prostate

IV. The cancer has spread to nearby tissues and organs

The TNM staging stops here, but keep in mind that the next step after this would be that the cancer has spread to other body parts, such as the brain, lungs, or bones. I will go into more detail on how a doctor determines the stage and what each one means in another post when the time comes, but this is just an introduction to the concept.

Here is a video about what cancer and prostate cancer is. It talks about some things I have not discussed yet (such as possible causes), so I recommend watching up until that point:

Sources:

AsapScience (June 16, 2012). How Prostate Cancer Works. Retrieved from https://www.youtube.com/watch?v=7_5MnsdQeQs.

National Cancer Institute (September 12, 2014). Prostate Cancer Treatment. General Information about Prostate Cancer. Retrieved from http://www.cancer.gov/cancertopics/pdq/treatment/prostate/Patient.

Reding, Kerryn. (PhD, MPH, Lecture director) (October 2014). Neoplasia. Lecture conducted from the University of Washington School of Nursing, Seattle.

First things first: What is cancer?

Characteristics of Cancer Cells:

Before I discuss prostate cancer, I am going to talk a little bit about what cancer is. This is a very broad topic, so I will try to make it as brief as I can. There are over 100 different types of cancer, so when someone says they have "cancer," they likely have something different than another person who has "cancer." This is because different types of cancer are unique. Simply put, cancer is a very broad term that refers to cells in your body that grow and act differently than your normal cells would. They are cells that have changed from normal cells due to changes in their DNA, which is the genetic information that tells every living cell how it should live/what it should do. Cancer cells function abnormally and thus cause harm to the body. While different types of cancer vary in where they grow, how they affect a patient's survival rate, and more, cancer cells have several specific characteristics in common that help them survive in our bodies. I am going to mention just a few of them:

1) They can keep multiplying over and over again. In other words, they are "immortal." Normal cells in the body receive special messages that tell them when to stop dividing and/or to die. This is healthy because if any cell keeps on dividing, there is a greater chance that it can mutate into something it shouldn't be because there are more chances for a random error to happen. It is also good because if a cell becomes "sick" in our body, these signals will cause it to self-destruct so that the rest of our cells are protected from it. However, cancer cells are actually able to ignore these signals! They can keep on growing and growing.

2) They can recruit nutrients (good things in our body such as vitamins that help us grow and stay healthy) by creating pathways for blood to flow to them. This is called "angiogenesis." Nutrients pass through the blood stream before they are delivered to our bodies' cells, and cancer cells selfishly find ways to steal them for themselves so that they can keep growing and become harder to kill.

3) They can often actually escape destruction from our immune cells, the cells that fight bad cells, viruses, bacteria and other germs in our bodies. In other words, cancer cells are sneaky and hard to kill.

Cancer Staging

There are several different tools used to stage cancer. The first one I am going to discuss is Summary Staging. Many cancer registries use this type of staging. Here it is:

Stage 1- In Situ: 

In this stage, the abnormal cells exist only in the layer of cells they originated/started growing in.

Stage 2- Localized: In this stage, the cancer is limited to the organ or tissue it started growing in and there is no evidence that it has spread beyond it. Examples of organs are the skin, colon, liver, lung, prostate, etc.

Stage 3- Regional: In this stage, the cancer has moved from the primary site it was once contained within and it has now spread to nearby lymph nodes or other organs or tissues in the body. If cancer cells get into lymph nodes, they can travel throughout lymph, an important fluid that travels throughout our bodies. This makes it easier for cancer cells to spread to other parts of the body, which we really do not want to happen.

Stage 4- Distant: In this stage, the cancer has moved from its primary location to distant organs, tissues, or lymph nodes. 

Another common method of staging is TNM staging, which looks at the extent of the Tumor, if cancer cells have spread to nearby lymph Nodes, and if it has spread ("Metastasized") to distant areas (side note: a tumor is a mass of abnormal cells. These cells might be cancerous or they might not be; Remember, cancer cells are defined by being cells that no longer perform normally. A tumor may also have abnormal cells that still keep some of their normal functions, therefore they are not considered cancerous, although they have the potential to be in the future.) There are 5 stages in the TNM staging: 0, I, II, III, or IV (0, 1, 2, 3, 4). 0 Means the tumor is "in situ," which I defined earlier, and 4 means it is metastatic (it has spread distally/far in the body).

Sources:

American Cancer Society (2014, December 22). What is Cancer? Retrieved from http://www.cancer.org/cancer/prostatecancer/detailedguide/prostate-cancer-what-is-cancer

Huether, S., & McCance, K. (2008). 9. In Understanding pathophysiology(4th ed., pp. 222-252). St. Louis, Mo.: Mosby/Elsevier.

Reding, Kerryn. (PhD, MPH, Lecture director) (October 2014). Neoplasia. Lecture conducted from the University of Washington School of Nursing, Seattle.