Prostate cancer is the most commonly diagnosed cancer among American men.i In the U.S., it is estimated that one out of every six men will develop prostate cancer. Annually, over 200,000 men are expected to be diagnosed with the disease. Advances in early detection and treatment methods appear to have improved survival rates. There are many options for men diagnosed with prostate cancer. In order to make informed choices, it is important for one to learn as much as one can about the disease and its management.
The prostate is one of the male sex glands, about the size of a walnut and located in front of the rectum and just below the bladder. The prostate has two lobes, the right and the left, which surround the upper part of the urethra, the tube that carries both urine and semen out through the penis. The prostate's job is to add nutrients and protective fluid to the sperm, helping to create semen. Male sex hormones, such as testosterone, regulate the functions of the prostate, stimulating activity and helping keep the prostate cancer cells healthy.
See an illustration.
A breakdown in the cells' normal control mechanisms is usually to blame for the development of cancer cells. Cancer is most frequently caused by damage to one or more of a cell's genes. Genetic mutations (changes to the genes) may lie hidden within a cell for many years. During this time, the mutated genes may be held in check by the cells' normal regulatory mechanisms. However, excessive mutations and/or damage to genes controlling the regulatory functions can trigger serious changes in cell growth and behavior that could result in cancer.
Prostate cancer is a complex disease that predominantly affects older men. Changes in prostate cells contribute to the disease's development and progression. Because these changes are not yet completely understood, the course of the cancer is still often difficult to predict in individual men. The rate of tumor growth can vary.
The cause of prostate cancer is unknown. However, it is known that the growth of cancer cells in the prostate, like that of normal prostate cells, is stimulated by male hormones, especially testosterone. Approximately 95% of the testosterone produced in the body is made by the testes (about 95%). The adrenal glands (small glands that sit above each kidney) produce hormones that are converted to testosterone and this accounts for the remaining 5% of testosterone in the body.
Compared with other types of cancer, generally, prostate cancer is relatively slow growing. A man with prostate cancer may live for many years without ever having the cancer discovered. In fact, many men with prostate cancer will not die from it but with it. As a man gets older, his risk of developing prostate cancer increases. About 2/3 of prostate cancers are diagnosed in men over 65 years of age.
Prostate cancer does not develop overnight but slowly emerges over time as a result of progressive changes in cell structure and behavior. In fact, one of the first changes in tissue appearance is known as prostatic intraepithelial neoplasia, or PIN. PIN is a precancerous growth of the cells that line the internal and external surfaces of the prostate.
Cells affected by PIN are distinctive and PIN is visible to a pathologist under a microscope. PIN is often classified as low or high grade, depending on the degree of abnormality visible. In the absence of malignant cells, finding high-grade PIN may impact a doctor's decision-making.
As the abnormalities associated with PIN develop and progress, an imbalance begins to evolve between cell growth and death. Abnormal cells begin to increase in quantity. In most cases, mutations in genes regulating the growth of prostate cells, that is, oncogenes and tumor suppressor genes, trigger the imbalance. As the process progresses, a breakdown of regulatory mechanisms can allow for accelerated and unregulated growth of cancerous cells.
Oncogenes. Oncogenes are genes that when overactive promote the formation of cancer through increased cell growth, decreased cell death or a combination of both. As such, scientists are studying ways to identify the oncogenes that are activated in prostate cancer. Such information will likely prove extremely valuable in the early detection and management of this disease.
Tumor Suppressor Genes. Tumor suppressor genes are genes that when underactive promote the formation of cancer through increased cell growth, decreased cell death, or a combination of both. Genetic mutations impair the ability of tumor suppressor genes to perform their function, allowing for abnormal and uncontrolled cellular growth.
Tumor Metastasis. Cancer cells that have become very abnormal can break off from a tumor and spread (also known as metastasize). Sites where prostate cancer tends to spread are the lymph nodes, various bones (especially the bones of the hip and lower back), lungs, and occasionally the brain. Cancer cells that have spread to other areas of the body can form tumors that can expand and squeeze other body parts. For example, when prostate cancer spreads to the bones, the most common symptom is bone pain.
Prostate cancer is the most common cancer among American men. How tumor suppressor genes and oncogenes contribute to the development of cancer is still being investigated. Researchers are discovering cellular changes that in some cases precede the development of invasive prostate cancer. Prostate cancer has the potential to spread (metastasize) to distant parts of the body. There are many options for men diagnosed with prostate cancer. Information on detection and treatment options can be found in other sections.
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a Black, PC, Penson, DF. Prostate Cancer on the Internet-Information or Misinformation? J Urol. 2006; 175:1836-1842.
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Print the page i American Cancer Society. Cancer Facts & Figures 2007. Atlanta: American Cancer Society, 2007.
ii American Cancer Society. Detailed Guide: Prostate Cancer. Available here. Accessed February 7, 2007.
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