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Types of Cancer > Prostate Cancer > Overview
Prostate Cancer: The Basics
Christopher Dolinsky, MD
Affiliation:
The Abramson Cancer Center of the University of Pennsylvania
Last Modified: February 23, 2007
What is the prostate?
The prostate is a small gland that only men have. It is normally about the size of a walnut. The prostate is located underneath the bladder and in front of the rectum. Because the prostate is close to the rectum, it can be felt by a doctor during a digital rectal exam (the part of a physical where the doctor inserts a gloved, lubricated finger into a man's anus). The prostate makes and stores fluid that is part of semen, and this fluid is released from a man's penis during ejaculation. The prostate is signaled to do its job by the male hormone testosterone, which can influence the behavior of the prostate gland and prostate cancer. Nerves to the penis that are important in producing and maintaining an erection run very close to the prostate. The prostate completely encircles the tube that carriers urine from the bladder to the penis, called the urethra. If the prostate enlarges, it can block the flow of urine from the bladder making it difficult for a man to urinate.
What is prostate cancer?
Prostate cancer happens when cells in the prostate begin to grow out of control and can then invade nearby tissues or spread throughout the body. Large collections of this out of control tissue are called tumors. However, some tumors are not really cancer because they cannot spread or threaten someone's life. These are called benign tumors. The tumors that can spread throughout the body or invade nearby tissues are considered cancer and are called malignant tumors. Usually, prostate cancer is very slow growing. However, sometimes it will grow quickly and spread to nearby lymph nodes. Lymph nodes are small, pea-sized pieces of tissue that filter and clean lymph, a clear liquid waste product. If prostate cancer has spread to your lymph nodes when it is diagnosed, it means that there is higher chance that it has spread to other areas of the body.
Am I at risk for prostate cancer?
Every man over the age of 45 is at risk for prostate cancer. Although prostate cancer can occasionally strike younger men, the risk of getting prostate cancer increases with age and more than 70% of men diagnosed with prostate cancer are over the age of 65. Prostate cancer is the most common cancer that men get in the United States behind skin cancer. It is estimated that there will be 189,000 new cases of prostate cancer and 30,200 deaths from prostate cancer in the year 2002 in the United States.
Although there are several known risk factors for getting prostate cancer, no one knows exactly why one man gets it and another doesn't. Some of the most important risk factors for prostate cancer include age, ethnicity, genetics and diet. Age is generally considered the most important risk factor for prostate cancer. The incidence of prostate cancer rises quickly after the age of 60, and the majority of men will have some form of prostate cancer after the age of 80. One of the sayings about prostate cancer is that older men (over the age of 80) die with prostate cancer not from prostate cancer. This saying means that many older men have microscopic disease that doesn't shorten their life expectancy because the cancer takes a long time to grow and become clinically important. However, this saying is only a generalization; sometimes prostate cancer can grow quickly even in older patients.
Another important risk factor for prostate cancer is ethnicity. No one knows exactly why, but prostate cancer is more common in African-American and Latino men than Caucasian men. African-American men have a 1.6 fold higher chance of getting and dying from prostate cancer than Caucasian men. Asian and Native American men have the lowest chances of getting prostate cancer. Some doctors believe that genetic differences are important in explaining the different rates of prostate cancer between different ethnic groups; however, there is some evidence that differences in diets may be the cause. When Asian men move to Western countries like the United States, their chances of getting prostate cancer rise. Men who live in the United States and Northern Europe have the highest rates of prostate cancer, while men who live in South America, Central America, Africa, and Asia all have much lower chances of developing prostate cancer.
There is some evidence that a man's diet may affect his risk of developing prostate cancer. The most common dietary culprit implicated in raising prostate cancer risk is a high fat diet, particularly a diet high in animal fats. Also, a few studies have suggested that a diet low in vegetables causes an increased risk of prostate cancer. There are a few foods that have been implicated in decreasing prostate cancer risk: a diet high in tomatoes (lycopene) has been suggested as well as diet high in omega-3-fatty acids (oils found in fish like salmon and mackerel). Doctors and scientists aren't in full agreement as to the usefulness of eating these foods when in comes to decreasing prostate cancer risk. Diets high in selenium, vitamin D, and soy have all been suggested to decrease prostate cancer risk; but a these are currently under study and data from large trials is needed before firm recommendations can be given about their use for this purpose.
A family history of prostate cancer increases a man's chances of developing the disease. This increase shows itself when a man has either a father or brothers (or both) with prostate cancer, and is even greater when his relatives develop prostate cancer at a young age. A variety of different genetic factors are currently being researched. Variations and mutations in certain genes may be responsible for some increases in prostate cancer rates in families. Men who carry mutations in genes known as BRCA1 or BRCA2 (these are genes implicated in breast and ovarian cancer in women) may have a 2 to 5 fold increase in prostate cancer risk. Men with high levels of testosterone or a hormone known as IGF-1 (insulin-like growth factor 1) seem to be at a higher risk for developing prostate cancer as well.