Prostate Cancer, meaning and as it affects men
What Is Prostate Cancer?
Cancer starts when cells in the body begin to grow out of control. Cells in nearly any part of the body can become cancer cells, and can then spread to other areas of the body. To learn more about cancer and how it starts and spreads, see What Is Cancer?
Prostate cancer begins when cells in the prostate gland start to grow out of control. The prostate is a gland found only in males. It makes some of the fluid that is part of semen.
The prostate is below the bladder (the hollow organ where urine is stored) and in front of the rectum (the last part of the intestines). Just behind the prostate are glands called seminal vesicles that make most of the fluid for semen. The urethra, which is the tube that carries urine and semen out of the body through the penis, goes through the center of the prostate.
The size of the prostate can change as a man ages. In younger men, it is about the size of a walnut, but it can be much larger in older men.
Types of prostate cancer
Almost all prostate cancers are adenocarcinomas. These cancers develop from the gland cells (the cells that make the prostate fluid that is added to the semen).
Other types of cancer that can start in the prostate include:
- Small cell carcinomas
- Neuroendocrine tumors (other than small cell carcinomas)
- Transitional cell carcinomas
These other types of prostate cancer are rare. If you are told you have prostate cancer, it is almost certain to be an adenocarcinoma.
Some prostate cancers grow and spread quickly, but most grow slowly. In fact, autopsy studies show that many older men (and even some younger men) who died of other causes also had prostate cancer that never affected them during their lives. In many cases, neither they nor their doctors even knew they had it.
Possible pre-cancerous conditions of the prostate
Some research suggests that prostate cancer starts out as a pre-cancerous condition, although this is not yet known for sure. These conditions are sometimes found when a man has a prostate biopsy (removal of small pieces of the prostate to look for cancer).
Prostatic intraepithelial neoplasia (PIN)
In PIN, there are changes in how the prostate gland cells look when seen with a microscope, but the abnormal cells don’t look like they are growing into other parts of the prostate (like cancer cells would). Based on how abnormal the patterns of cells look, they are classified as:
- Low-grade PIN: The patterns of prostate cells appear almost normal.
- High-grade PIN: The patterns of cells look more abnormal.
Low-grade PIN is not thought to be related to a man’s risk of prostate cancer. On the other hand, high-grade PIN is thought to be a possible precursor to prostate cancer. If you have a prostate biopsy and high-grade PIN is found, there is a greater chance that you might develop prostate cancer over time.
PIN begins to appear in the prostates of some men as early as in their 20s. But many men with PIN will never develop prostate cancer.
For more on PIN, see Tests to Diagnose and Stage Prostate Cancer.
Proliferative inflammatory atrophy (PIA)
In PIA, the prostate cells look smaller than normal, and there are signs of inflammation in the area. PIA is not cancer, but researchers believe that PIA may sometimes lead to high-grade PIN, or perhaps directly to prostate cancer.
What Causes Prostate Cancer?
Researchers do not know exactly what causes prostate cancer. But they have found some risk factors and are trying to learn just how these factors might cause prostate cells to become cancer cells.
On a basic level, prostate cancer is caused by changes in the DNA of a normal prostate cell. DNA is the chemical in our cells that makes up our genes, which control how our cells function. We usually look like our parents because they are the source of our DNA. But DNA affects more than just how we look.
Some genes control when our cells grow, divide into new cells, and die:
- Certain genes that help cells grow, divide, and stay alive are called oncogenes.
- Genes that normally keep cell growth under control, repair mistakes in DNA, or cause cells to die at the right time are called tumor suppressor genes.
Cancer can be caused by DNA mutations (or other types of changes) that keep oncogenes turned on, or that turn off tumor suppressor genes. These types of gene changes can lead to cells growing out of control.
DNA changes can either be inherited from a parent or can be acquired during a person’s lifetime.
Inherited gene mutations
Some gene mutations can be passed from generation to generation (inherited) and are found in all cells in the body. Inherited gene changes are thought to play a role in about 10% of prostate cancers. Cancer caused by inherited genes is called hereditary cancer. Several inherited mutated genes have been linked to hereditary prostate cancer, including:
- BRCA1 and BRCA2: These tumor suppressor genes normally help repair mistakes in a cell’s DNA (or cause the cell to die if the mistake can’t be fixed). Inherited mutations in these genes more commonly cause breast and ovarian cancer in women. But changes in these genes (especially BRCA2) also account for a small number of prostate cancers.
- CHEK2, ATM, PALB2, and RAD51D: Mutations in these other DNA repair genes might also be responsible for some hereditary prostate cancers.
- DNA mismatch repair genes (such as MSH2, MSH6, MLH1, and PMS2): These genes normally help fix mistakes (mismatches) in DNA that can be made when a cell is preparing to divide into 2 new cells. (Cells must make a new copy of their DNA each time they divide.) Men with inherited mutations in one of these genes have a condition known as Lynch syndrome (also known as hereditary non-polyposis colorectal cancer, or HNPCC), and are at increased risk of colorectal, prostate, and some other cancers.
- RNASEL (formerly HPC1): The normal function of this tumor suppressor gene is to help cells die when something goes wrong inside them. Inherited mutations in this gene might let abnormal cells live longer than they should, which can lead to an increased risk of prostate cancer.
- HOXB13: This gene is important in the development of the prostate gland. Mutations in this gene have been linked to early-onset prostate cancer (prostate cancer diagnosed at a young age) that runs in some families. Fortunately, this mutation is rare.
Other inherited gene mutations may account for some hereditary prostate cancers, and research is being done to find these genes.
Acquired gene mutations
Some genes mutate during a person’s lifetime, and the mutation is not passed on to children. These changes are found only in cells that come from the original mutated cell. These are called acquired mutations. Most gene mutations related to prostate cancer seem to develop during a man’s life rather than having been inherited.
Every time a cell prepares to divide into 2 new cells, it must copy its DNA. This process isn’t perfect, and sometimes errors occur, leaving defective DNA in the new cell. It’s not clear how often these DNA changes might be random events, and how often they are influenced by other factors (such as diet, hormone levels, etc.). In general, the more quickly prostate cells grow and divide, the more chances there are for mutations to occur. Therefore, anything that speeds up this process may make prostate cancer more likely.
For example, androgens (male hormones), such as testosterone, promote prostate cell growth. Having higher levels of androgens might contribute to prostate cancer risk in some men.
Some research has found that men with high levels of another hormone, insulin-like growth factor-1 (IGF-1), are more likely to get prostate cancer. However, other studies have not found such a link. Further research is needed to make sense of these findings.
As mentioned in Prostate Cancer Risk Factors, some studies have found that inflammation in the prostate might be linked to prostate cancer. One theory is that inflammation might lead to cell DNA damage, which could contribute to a normal cell becoming a cancer cell. More research is needed in this area.
Prostate Cancer Risk Factors
A risk factor is anything that raises your risk of getting a disease such as cancer. Different cancers have different risk factors. Some risk factors, like smoking, can be changed. Others, like a person’s age or family history, can’t be changed.
But having a risk factor, or even several, does not mean that you will get the disease. Many people with one or more risk factors never get cancer, while others who get cancer may have had few or no known risk factors.
Researchers have found several factors that might affect a man’s risk of getting prostate cancer.
Prostate cancer is rare in men younger than 40, but the chance of having prostate cancer rises rapidly after age 50. About 6 in 10 cases of prostate cancer are found in men older than 65.
Prostate cancer develops more often in African-American men and in Caribbean men of African ancestry than in men of other races. And when it does develop in these men, they tend to be younger. Prostate cancer occurs less often in Asian-American and Hispanic/Latino men than in non-Hispanic whites. The reasons for these racial and ethnic differences are not clear.
Prostate cancer is most common in North America, northwestern Europe, Australia, and on Caribbean islands. It is less common in Asia, Africa, Central America, and South America.
The reasons for this are not clear. More intensive screening for prostate cancer in some developed countries probably accounts for at least part of this difference, but other factors such as lifestyle differences (diet, etc.) are likely to be important as well. For example, Asian Americans have a lower risk of prostate cancer than white Americans, but their risk is higher than that of men of similar ethnic backgrounds living in Asia.
Prostate cancer seems to run in some families, which suggests that in some cases there may be an inherited or genetic factor. Still, most prostate cancers occur in men without a family history of it.
Having a father or brother with prostate cancer more than doubles a man’s risk of developing this disease. (The risk is higher for men who have a brother with the disease than for those who have a father with it.) The risk is much higher for men with several affected relatives, particularly if their relatives were young when the cancer was found.
Several inherited gene changes (mutations) seem to raise prostate cancer risk, but they probably account for only a small percentage of cases overall. For example:
- Inherited mutations of the BRCA1 or BRCA2 genes, which are linked to an increased risk of breast and ovarian cancers in some families, can also increase prostate cancer risk in men (especially mutations in BRCA2).
- Men with Lynch syndrome (also known as hereditary non-polyposis colorectal cancer, or HNPCC), a condition caused by inherited gene changes, have an increased risk for a number of cancers, including prostate cancer.
Other inherited gene changes can also raise a man’s risk of prostate cancer. For more on some of these gene changes, see What Causes Prostate Cancer?
Factors with less clear effect on prostate cancer risk
The exact role of diet in prostate cancer is not clear, but several factors have been studied.
Men who eat a lot of red meat or high-fat foods (especially dairy products) appear to have a slightly higher chance of getting prostate cancer. These men also tend to eat fewer fruits and vegetables. Doctors aren’t sure which of these factors is responsible for raising the risk.
Some studies have suggested that men who consume a lot of calcium (through food or supplements) may have a higher risk of developing prostate cancer. Dairy foods (which are often high in calcium) might also increase risk. But most studies have not found such a link with the levels of calcium found in the average diet, and it’s important to note that calcium is known to have other important health benefits.
Being obese (very overweight) does not seem to increase the overall risk of getting prostate cancer.
Some studies have found that obese men have a lower risk of getting a low-grade (slower growing) form of the disease, but a higher risk of getting more aggressive (faster growing) prostate cancer. The reasons for this are not clear.
Some studies have also found that obese men may be at greater risk for having more advanced prostate cancer and of dying from prostate cancer, but not all studies have found this.
Most studies have not found a link between smoking and getting prostate cancer. Some research has linked smoking to a possible small increased risk of dying from prostate cancer, but this finding needs to be confirmed by other studies.
There is some evidence that firefighters can be exposed to chemicals that may increase their risk of prostate cancer.
A few studies have suggested a possible link between exposure to Agent Orange, a chemical used widely during the Vietnam War, and the risk of prostate cancer, although not all studies have found such a link. The National Academy of Medicine considers there to be “limited/suggestive evidence” of a link between Agent Orange exposure and prostate cancer. To learn more, see Agent Orange and Cancer.
Inflammation of the prostate
Some studies have suggested that prostatitis (inflammation of the prostate gland) may be linked to an increased risk of prostate cancer, but other studies have not found such a link. Inflammation is often seen in samples of prostate tissue that also contain cancer. The link between the two is not yet clear, and this is an active area of research.
Sexually transmitted infections
Researchers have looked to see if sexually transmitted infections (like gonorrhea or chlamydia) might increase the risk of prostate cancer, because they can lead to inflammation of the prostate. So far, studies have not agreed, and no firm conclusions have been reached.
Some studies have suggested that men who have had a vasectomy (minor surgery to make men infertile) have a slightly increased risk for prostate cancer, but other studies have not found this. Research on this possible link is still under way.
Culled from cancer.org