Causes and Risk Factors of Prostate Cancer

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Prostate cancer begins when a series of gene mutations in a prostate cell's DNA cause the cell to grow and divide in an out-of-control fashion. The exact cause(s) have yet to be determined, but it's thought that most prostate cancers develop due to a combination of factors that work together.

Known risk factors for the disease include age, race, and geographical location. Researchers are also looking into potential connections to environmental exposures to pesticides and herbicides, diet, vitamin D deficiency, and even sexual activity. A family history of prostate cancer and certain genetic mutations are also associated with the development of prostate cancer at a younger age.

prostate cancer causes and risk factors
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Common Risk Factors

The accumulating cancer cells that result from this growth form a tumor that can eventually invade nearby tissue and sometimes break off and spread (metastasize) to other regions of the body. But again, what causes this in the first place is not concrete.

Risk factors are conditions that are associated with an increased risk of developing prostate cancer but do not necessarily cause prostate cancer.

Men who have more risk factors may wish to be screened more often or at an earlier age than men without these risk factors. That said, prostate cancer can and does occur in men who do not have any obvious risk factors, and any man is potentially at risk for the disease. Possible risk factors include:

Age

The risk of prostate cancer increases with age, and roughly 80 percent of men are diagnosed after the age of 65. It is uncommon before the age of 40, and when seen in younger men, is often associated with a family history of the disease in male relatives or breast cancer in female relatives.

prostate cancer: newly diagnosed cases
Illustration by Verywell

Race

Black men have a greater risk of prostate cancer than do men of other races and are more likely to develop the disease at a young age. In black men, prostate cancer is also more likely to be aggressive, though the reason for this is unclear.

American Asian and Hispanic men have a lower risk of prostate cancer than their non-Hispanic white counterparts. Factors other than ethnicity are likely involved, since Asian-American men have a higher incidence of prostate cancer than Asian men living in Asia, and the incidence of prostate cancer in Asian men living in the United States and Europe is currently increasing.

Geography

Prostate cancer is more common in some areas of the world, with a higher incidence in North America, Europe, and Australia than other regions. 

Possible Risk Factors

In addition to the known risk factors, there are a number of factors that are being investigated as to their potential role in either increasing or reducing the risk of prostate cancer.

Diet

The role of diet in the development of prostate cancer has long been debated. It appears that a diet rich in red meats and dairy products, as well as high in calcium, may be associated with an increased risk (though not all studies have found these associations). Conversely, a diet rich in fruits and vegetables may have a protective effect.

In addition to a possible link with the development of prostate cancer, dairy products have been linked with poorer outcomes in men who already have the disease. Whole milk consumption was found to be associated with an increased risk of prostate cancer recurrence in men who already have the disease, according to a 2017 study. A 2015 study found that men who continued to consume a Western diet after a diagnosis of prostate cancer had an increased risk of death.

Environmental Exposures

Some occupational exposures or occupations have been linked to the development of prostate cancer. These include:

  • Cadmium: The risk related to cadmium exposure appears to be enhanced by a zinc deficiency in the diet.
  • Herbicides: In the past, the possible role of Agent Orange exposure in prostate cancer was controversial, but more recent research reveals a more consistent association between exposure and prostate cancer. Exposed veterans have at least a 50 percent greater risk of developing prostate cancer, and cancers that occur tend to be more aggressive and more likely to metastasize.
  • Pesticides: Men who apply pesticides or work in the production of pesticides may have an increased risk of prostate cancer. This increased risk, according to a 2015 study, is primarily in men who also have a family history of the disease.
  • Smoke: There are a number of different compounds in smoke exposure that may contribute to this increased risk in firefighters.

There are likely environmental factors that have not yet been identified that play a role in the development of prostate cancer. Of note, men who have a brother with prostate cancer have a higher risk of the disease than men who have a father with the disease (both fathers and brothers are considered first-degree relatives). This suggests that the increased risk in a brother versus a father is due to environmental factors.

Vitamin D Deficiency/Sun Exposure

Vitamin D is a vitamin that acts more like a hormone in the body and is produced in the skin upon exposure to ultraviolet light from the sun. It's been known for some time that men who live in northern regions are more likely to develop the disease than those in southern latitudes, and this increased risk is thought by some to be related to vitamin D deficiency

Other research has suggested that high serum vitamin D levels may reduce the risk of aggressive prostate cancer. Fortunately, vitamin D levels can be tested a via a simple blood test, and men can talk to their doctors about supplementation if needed.

Sexual Activity

At one time it was thought that men who were more sexually active (had more ejaculations per month) were more likely to develop prostate cancer. The thought was that these men may be more likely to develop a sexually transmitted disease that could cause inflammation in the prostate and, hence, lead to cancer, or that they had higher testosterone levels (testosterone can "feed" the growth of prostate cancers).

This myth has been dispelled in a few large studies, and according to a 2016 follow-up study, men who have more ejaculations per month (21 in the study) appeared to have a significantly lower risk of developing prostate cancer than those who had fewer (four to seven or less).

With colon cancer, less frequent bowel movements are associated with an increased risk of the disease, presumably because toxins in stool are in contact with the mucosa of the bowel for a longer period of time. The same principle could be at play with prostate cancer, with fewer ejaculations resulting in any carcinogens present having longer contact with the tissues in the prostate.

Prostatitis 

Chronic prostatitis secondary to sexually transmitted infections has been correlated with an increased risk of prostate cancer, though no specific organism has been identified. 

Other Concerns

You may also hear of other potential risk factors for prostate cancer. It's important to sort the fact from fiction:

  • Vasectomy: The possibility that vasectomy is associated with prostate cancer has been debated for some time, though more recent studies have found no correlation between either vasectomy or vasectomy reversal and the occurrence of prostate cancer.
  • Immunosuppression: A compromised immune system, due to conditions such as HIV/AIDS or other causes, has not been linked with an increased risk of prostate cancer, but prostate cancers that do occur may be more aggressive.
  • Obesity: Men who are overweight or obese do not appear to have a greater risk of developing prostate cancer, but an elevated body mass index has been linked with tumors that are more aggressive and more difficult to treat.

Genetics

Genetics clearly play a role in prostate cancer. Several gene mutations have been linked to the development of prostate cancer, but not all men who have a family history of the disease will have a detectable mutation.

The science looking at gene mutations and their role in cancer is in its infancy, and it's likely that there are a number of gene mutations associated with prostate cancer that has not yet been discovered. It's also possible that it is a combination of genetic factors that raise the risk for some men. That's a long way of saying that, even if a man does not have a known gene mutation, he should talk to his doctor if he has a relevant family history.

Family History

Men who have a father, brother or son who has prostate cancer have a higher risk of developing prostate cancer. The risk is greater if a male relative has had prostate cancer at a young age, or if many men in a family are affected.

It can be difficult to separate out genetics and environmental factors as a cause. Overall, around 20 percent of prostate cancers are considered "familial" and that could be due to a combination of shared genes and shared lifestyles.

Men who have a family history of breast cancer in female relatives also have an increased risk of developing the disease.

Gene Mutations and Genetic Syndromes

It's thought that between 5 percent and 10 percent of prostate cancers are related to inherited mutations for which testing is now available. The chance that a prostate cancer is hereditary is increased if at least three relatives have had prostate cancer. Some genetic changes associated with prostate cancer include:

  • BRCA gene mutations: Both BRCA1 gene mutations and BRCA2 gene mutations carry an increased risk of prostate cancer. It's important to note that both of these mutation types may be associated with different cancers in different family members. So, for example, your doctor may be more concerned that you have one of these mutations if you have young female relatives who have had breast cancer and another family member who has had pancreatic cancer than if you have a few male relatives who had prostate cancer at a later age.
  • Lynch syndrome (hereditary non-polyposis colorectal cancer or HNPCC): This syndrome is due to mismatched genes and is associated more strongly with colorectal cancer.
  • RNASEL mutations
  • HOXB13 mutations: These mutations are uncommon and are associated with prostate cancer in younger men.

Gene mutations can be confusing. It is not usually the gene mutation itself that gives rise to cancer. Many of the genes associated with an increased risk of cancer are tumor suppressor genes.

Tumor suppressor genes, such as the BRCA genes, code for proteins that work to repair damaged DNA or eliminate damaged cells from the body. When these proteins are abnormal, they are unable to do their job properly. Instead of being rightfully eliminated, a cell may progress to becoming a cancer cell.

People have two copies of each of the tumor suppressor genes, one inherited from each parent. Since both copies usually need to be mutated for cancer to develop, not everyone who inherits these mutations will develop cancer. Instead, they have a "genetic predisposition" to cancer. There is another type of gene, oncogenes, in which only one copy must be mutated, but this is much less common with regard to prostate cancer.

Whether or not you have a family history of prostate cancer, it's helpful to learn about hereditary cancer when looking at your risk of any type of cancer.

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