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prostate cancer, cancer originating in the prostate gland. Prostate cancer is one of the most common malignancies in men in the United States, second only to skin cancer, and as a cause of cancer death in men is second only to lung cancer. It occurs predominantly in men 65 years of age and older. Black men have a higher incidence than white men. The cause of prostate cancer is unknown, but the incidence varies markedly by geographic region, an indication that there are environmental factors that may trigger the disease. For example, men in China and Japan have a low rate of prostate cancer, but the incidence rises in Chinese and Japanese men who move to the United States. The hormone testosterone is believed to have a role in the development of prostate cancer, and studies have shown a relationship between high dietary fat intake and increased testosterone levels. Prostate tumors are often slow growing. Around 95% are classified as adenocarcinomas (arising from epithelial glandular tissue). The most common site of metastasis is the bone, and bone metastasis is the leading cause of death from prostate cancer.
Screening and Diagnosis
Traditionally, prostate cancer screening consisted of digital-rectal examination. Since 1986, however, a blood test for a tumor marker called prostate-specific antigen (PSA) has greatly increased the number of early-stage prostate cancers diagnosed. An elevated level of PSA can indicate the presence of prostatic malignancy. Elevated PSA is further investigated by an ultrasound test and needle biopsy, in which a fine needle is inserted into the gland and cells are extracted for laboratory analysis. In some cases a bone scan is also performed to rule out metastatic disease. Because PSA tests detect not only aggressive cancers but slow-growing cancers that are not life-threatening, many people disagree with routine PSA testing of asymptomatic men. A review of the test by a U.S. task force indicated that the test has led to treatments that compromise quality of life without assuring a longer life; the task force recommended (2011) that the test not be given to normal healthy men. An additional problem with the test is that some men with normal PSA levels will in fact have prostate cancer.
Very small cancers or slow-growing cancers in older men are now often watched and not treated unless there are changes in test results; most men who have prostate cancer do not usually die from it even if it is not treated. For most other patients with localized tumors, surgical removal of the prostate gland (prostatectomy) is the initial treatment, despite possible side effects of urinary incontinence and impotence. After surgery, a repeated blood test for protein-specific antigen can indicate whether any cancer remains. In metastatic disease, other treatments are employed depending on the stage of the disease and the age and health of the patient. Treatment options include external-beam radiation, implantation of radioactive isotopes, and palliative surgery. Hormonal manipulation by giving estrogens or other drugs, or by orchiectomy (removal of the testes), is sometimes used to decrease levels of testosterone.
See M. Korda, Man to Man (1996), and P. Walsh and J. F. Worthington, Dr. Patrick Walsh's Guide to Surviving Prostate Cancer (2001). See also publications of the National Cancer Institute and the American Cancer Society.
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