Factors that Increase Prostate Cancer Risk
The underlying cause of prostate cancer is unknown. As with other cancers, however, multiple events over a period of many years are probably necessary to produce a cancerous change in prostate cells.
The development of cancer is broadly viewed as a two-step process. The first step is initiation, when the cell is exposed to substances (such as a chemical), agents (such as a virus), or forces (such as radiation) that cause an alteration (mutation) in the genetic machinery of the cell. The second step is promotion, in which other chemicals, hormones, or diet and lifestyle patterns stimulate the growth and reproduction of the abnormal cell. A promoter does not set the process in motion, but it creates an environment favorable for the runaway growth that causes a cancerous tumor to form and progress.
Age, race, and family history are all important risk factors for prostate cancer. In addition, diet and lifestyle factors may influence whether a man will develop the disease. Studies have shown no clear association between the development of prostate cancer and regular alcohol intake (though binge drinking may increase the risk), smoking, vasectomy, or the presence of benign prostatic hyperplasia (BPH).
Increasing evidence suggests that fat intake, physical inactivity, or being overweight may influence the development or progression of prostate cancer. Some research suggests that the use of testosterone replacement therapy may promote the development of new prostate cancer. It is also believed to cause the disease to progress more rapidly in men who already have it.
Age and Prostate Cancer Risk
As a man ages, his risk of developing prostate cancer increases dramatically. This age-related increase is greater for prostate cancer than for any other type of cancer. The average age at diagnosis is between 65 and 70; the average age at death is between 77 and 80.
Race and Prostate Cancer Risk
The incidence of prostate cancer in the United States varies by race. Black men are at highest risk, with a rate of 249 per 100,000 men each year. The rate for white men is 150 per 100,000. Asian American men have a lower risk: 91 per 100,000.
Family History and Prostate Cancer Risk
Studies of identical and fraternal twins have found that prostate cancer has a stronger hereditary component than many other cancers, including breast and colon cancer. Having one first-degree relative (a brother or father) with prostate cancer doubles the risk of developing the disease; having a second-degree relative (an uncle or grandfather) with the disease confers only a small increase in risk.
A number of genetic mutations are linked to prostate cancer. The most well studied of these mutations are in a region of chromosome 1 known as HPC1. HPC1 may be involved in protecting against prostate inflammation. Some analyses suggest that mutations in HPC1 increase the risk of prostate cancer, but other studies have failed to find an association.
Other genes involved in how the body handles male hormones (androgens), its reaction to inflammation or infection, and its ability to process certain types of fat may also be important.
Rather than inheriting a defect in a single gene that results in prostate cancer, it is more likely that minor variations in a number of genes (any one of which alone may have no adverse effects) when combined may act like the "perfect storm" to increase a man's risk. The lifestyle choices a man makes during life most likely act in concert with these genetic variants to cause the development and progression of prostate cancer.
Although genes can influence a man's risk of developing prostate cancer, other factors also are at work. The likelihood that identical twins (who share all genetic information) will both develop prostate cancer is 19 to 27 percent. This suggests that lifestyle choices can modify the effects of the genetic cards that a person is dealt at birth.