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Prostate cancer is the most frequently diagnosed cancer in men aside from skin cancer. It is also the second leading cause of cancer deaths in men behind lung cancer. As frightening as that is, it’s important to remember that the majority of men who are diagnosed with prostate cancer will not die from their disease. Even the once dreaded side effects of prostate cancer treatment—the loss of sexual function and incontinence—are now far less severe and less common with the advances in treatment developed over the last decades.
Understandably, many men want to take a proactive approach to prostate cancer prevention and early detection. There’s no better way to do that than to understand the diseases causes and risk factors. Armed with this information, you will have a better idea if you are at higher than normal risk. From here, you and your doctor can make more informed decisions about screening and steps to reduce your risk.
- Age, family history and heritage are the most important risk factors for prostate cancer.
- Evidence also links diet and exposure to certain chemicals to prostate cancer risk.
- Men with higher risk may benefit more from prostate cancer screening than men with average risk, although this is not certain.
Prostate cancer risk factors
The three most important risk factors for prostate cancer are age, African American heritage, and family history (Gann, 2002). Time marches on and there’s nothing can change the genetic hand we’re dealt but that doesn’t mean we can’t take steps to lower risk and improve outlook as we’ll touch upon in a moment.
Prostate cancer is very rare before age 40 and becomes more common after 55. Why? Well, as we age, all of us rack up genetic mutations. The more these mutations accumulate, the more likely that enough mutations of the right combination will develop and lead to cancer. Getting older is a risk factor for acquired genetic mutations and genetic mutations lead to cancer.
Family history is a risk factor for prostate cancer due to inherited genes that increase the risk of prostate cancer. In most cases, the precise genes involved in elevating prostate cancer risk are unknown. What we do know is that people with one first degree relative with prostate cancer have 2–3 times the risk of prostate cancer. Having more relatives with prostate cancer, or relatives who were diagnosed at a young age, increases that risk even more.
It is unclear why having African American heritage increases the risk of developing, and dying from, prostate cancer. The average age of developing prostate cancer is also lower in African Americans. This may be due to genetic factors, environmental factors (such as diet), higher poverty rates, or limited access to healthcare. It may be a combination of some or all of these factors.
A growing body of evidence suggests that a Western lifestyle is a risk factor for prostate cancer. Prostate cancer rates are much higher in the Western world than in China and Japan. However, people of Japanese ancestry who live in Western countries have much higher rates of prostate cancer than those who live in Japan. Dietary factors might account for this, with high saturated fat intake from meat and dairy sources a likely culprit. There may also be specific nutrients, like lycopene (Rowles, 2017) and selenium (Cui, 2017), that may be protective from cancer that are deficient in Western diets.
Exposure to certain chemicals has been found to increase the risk of prostate cancer. These include agent orange and bisphenol A (BPA). Other possible risk factors for prostate cancer that have weaker evidence include obesity, chronic prostatitis (inflammation of the prostate), and sedentary lifestyle.
Acquired gene mutations in prostate cancer
All cancers are caused by genetic mutations in our cells. Genetic mutations are changes to our DNA. These can occur during replication of the DNA before cells divide or it can be caused by environmental factors that damage DNA, like cigarette smoking and ultraviolet light.
These mutations are what allow cancers to overcome the mechanisms that normal cells have to prevent them from growing out of control. Most of these mutations are acquired during a person’s lifetime and no single mutation allows a cell to become a cancer cell. It is the buildup of these mutations that eventually allows cancer cells (Hanahan, 2011) to:
- Have constant signals to grow and divide
- Escape the controls that normal cells use to prevent unregulated growth and division
- Replicate forever
- Resist cell death
- Produce signals to grow their own blood supply (called angiogenesis)
- Acquire the ability to invade other tissues and spread to organs far away from the original cancer site (metastasize), which is what usually causes death from cancer
These six things really boil down to two properties of cancers: uncontrolled growth and metastasis, which is the ability to invade and spread to sites distant from the original cancer. These acquired gene mutations can happen to anyone to produce a cancer, but there are certain specific risk factors for prostate cancer, as we’ll see.
Inherited gene mutations in prostate cancer
Aside from the majority of mutations that occur during a person’s lifetime, there are also mutations that can be inherited that increase the risk of prostate cancer. Two such mutations are mutations in the BRCA1 and BRCA2 genes. BRCA1 and BRCA2 are known as tumor suppressor genes, which means that when they are functioning normally they work to suppress tumor formation. They do this by helping repair damaged DNA.
BRCA1 and BRCA2 gene mutations can be inherited from either parent. They are well known for increasing breast and ovarian cancer risk in women, but they also increase the risk of some other cancers, including prostate cancer. Men with BRCA1 mutations have 3.5 times the risk of developing prostate cancer, and those with BRCA2 mutations have 8.6 times the risk (Castro, 2012). Also, men who are BRCA1 or BRCA2 positive tend to get more aggressive cancers than men who are negative and they are more likely to die of prostate cancer.
Another inherited mutation that increases the risk of prostate cancer is HOXB13 gene (Ewing, 2012). Exactly how the HOXB13 mutation causes cancer is not known.
BRCA1, BRCA2, and HOXB13 mutations are three well described genetic risks for prostate cancer, but there are likely many other inherited gene mutations that increase the risk of prostate cancer.
Prostate cancer screening and risk
Prostate cancer screening is a controversial topic because it is unclear whether screening decreases mortality (death). This is because many cancers are slow growing and will never cause a person problems even if they are not diagnosed and treated. Various medical organizations have made different prostate cancer screening recommendations, which can be quite confusing to men and their doctors alike.
The American Urological Association (AUA) recommends (Detection, 2018) that men aged 55–69 should engage in shared decision-making with their doctors when deciding whether to screen for prostate cancer. Shared-decision making is a process where doctors share the best available evidence, weighing the risks and benefits, so that a man can make an informed decision with his doctor’s support. The AUA also recommends that decisions about screening men aged 40–54 be individualized, with risk factors for prostate cancer (e.g., family history, African American) taken into consideration. The AUA does not recommend routine screening before age 40 or after age 70. Screening is performed by measuring prostate-specific antigen (PSA) levels, sometimes with a digital prostate exam.
The United States Preventive Services Task Force (USPSTF) has recommendations (USPSTF, 2018) that are very similar to the AUA. The American Academy of Family Practice (AAFP) recommends (AAFP, 2018) against routine screening for prostate cancer based on the small benefits and larger risks of screening. The AAFP is unclear about whether doctors should start the conversation about screening or should only screen if someone asks for it specifically.
Screening decisions are complex, but it is helpful to know your risk when deciding whether to screen for prostate cancer. Men with higher risk may benefit more from prostate cancer screening than men with average risk, although this is not certain. With information about your risks, goals, and values, you and your doctor can make the most informed decisions about prostate cancer screening.