Prostate cancer is a disease in which the cells of the prostate (a gland found in the male reproductive system) 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 in this way are said to be benign.
The prostate is a gland that produces the fluid (semen), which 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 a prostate cancer grows, some of the cells may break off and spread to other parts of the body through the lymphatic or the blood systems. This process is known as metastasis. The most common sites of spreading are the lymph nodes and various bones in the spine and the pelvic region.
The lymphatic system is composed of ducts that transport extracellular fluid from distant areas of the body to the heart. Fluid enters lymph ducts and travels toward the heart. Any fluid collected is mixed with the blood. Any excess fluid is eliminated from the blood by the kidneys. Along the lymph system are clusters of specialized tissue called lymph nodes. These nodes act as strainers and retain cellular debris to prevent it from entering the blood stream. Lymph nodes also retain cancer cells that escape from tumors. For this reason, surgeons often remove some lymph nodes for analysis to determine the extent that a cancer may have spread beyond its original (primary) site.
The cause of prostate cancer is not clear; however, several risk factors are known. The average age at diagnosis of prostate cancer is approximately 72 years. In fact, 80% of prostate cancer cases occur in men over the age of 65. As men grow older, the likelihood of developing 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 men is low, the rate in Japanese Americans is closer to that of white American men. This finding 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 such nutrients 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. These substances contain particularly high levels of molecules called antioxidants, which seem to oppose the formation of cancer cells. Vasectomy may be linked to increased prostate cancer rates as well. Workers in such industries 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.
L. Fleming Fallon Jr., MD, DrPH, The Gale Group Inc., Gale, Detroit,