Prostate cancer Health Article

Definition

The prostate, a gland found only in men, is part of the reproductive system. Prostate cancer is a disease in which the cells of the prostate become abnormal and start to grow uncontrollably, forming tumors. Tumors that can spread to other parts of the body are called malignant tumors or cancers. Tumors that are not capable of spreading are said to be benign.

Description

The prostate is a gland that produces the semen, the fluid that contains sperm. The prostate is about the size of a walnut and lies just beneath the urinary bladder. Usually prostate cancer is slow growing, but it can grow faster in some instances. As the prostate cancer grows, some of the cells break off and spread to other parts of the body through the lymphatic or the blood systems. This is known as metastasis. The most common sites of spreading are the lymph nodes and various bones in the spine and pelvic region.

The cause of prostate cancer is not clear; however, several risk factors are known. The average age at diagnosis of prostate cancer is around 72. In fact, 80% of prostate cancer cases occur in men over the age of 65. As men grow older, the likelihood of getting prostate cancer increases. Hence, age appears to be a risk factor for prostate cancer. Race may be another contributing factor. African-Americans have the highest rate of prostate cancer in the world, while the rate in Asians is one of the lowest. However, although the rate of prostate cancer in native Japanese is low, the rate in Japanese-Americans is closer to that of white American men. This suggests that environmental factors also play a role in prostate cancer.

There is some evidence to suggest that a diet high in fat increases the risk of prostate cancer. Studies also suggest that nutrients such as soy isoflavones, vitamin E, selenium, vitamin D and carotenoids (including lycopene, the red color agent in tomatoes and beets) may decrease prostate cancer risk. Vasectomy may be linked to increased prostate cancer rates as well. Workers in industries, such as welding, with exposure to the metal cadmium appear to have a higher than average risk of prostate cancer. Male sex hormone levels also may be linked to the rate of prostate cancer. In addition, some studies have linked increased prostate cancer risk to smoking.

Genetic profile

An estimated 5–10% of prostate cancer is due to a hereditary cause. Among men with early prostate cancer, a hereditary cause is likely in up to a third of cases before age 60, and almost half of men diagnosed at age 55 or less. Studies have found around a two- to three-fold increased rate of prostate cancer in close relatives of men with the disease. Hereditary prostate cancer is likely in a family if there are three cases of prostate cancer in close relatives or three affected generations (either mother's or father's side), or two relatives with prostate cancer before age 55.

Studies suggest that hereditary prostate cancer is likely to be caused by several different genes instead of a single gene. A gene, HPC1 (hereditary prostate cancer gene 1), located on the first chromosome pair at 1q24-25, was the first gene suggested to cause hereditary prostate cancer. At least four other genes have been reported, including one thought to increase the risk of both prostate and brain tumors. Other genes known to increase the risk of other cancers, such as breast cancer, may also be linked to increased prostate cancer risk. Common variations in certain genes also may increase susceptibility to prostate cancer including one gene linked to male sex hormones. Since no clear cause has been identified for the majority of hereditary prostate cancer, genetic testing, as of 2001, is typically done through research studies.

Demographics

Prostate cancer is the most common cancer among men in the United States, and is the second leading cause of cancer deaths. The American Cancer Society estimates that in 2001, 198,100 new cases of prostate cancer will be diagnosed, and it will cause 31,500 deaths. One in six men in the United States will be diagnosed with prostate cancer. Prostate cancer affects African-American men about twice as often as it does Caucasian men, and the mortality rate among African-Americans is also higher. African-Americans have the highest rate of prostate cancer in the world. The prostate cancer rate varies considerably around the world. The highest rates are in North America and Western Europe, whereas the rates are moderate in Africa and lowest in Asia. It is unclear what roles genetics, diet, economics, and health care access play in these rates.