prostate cancer, cancer originating in the prostate gland. Prostate cancer is the leading malignancy in men in the United States and is second only to lung cancer as a cause of cancer death in men. It occurs predominantly in older men; the median age at diagnosis is 72 years. 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.

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, fearing that the test might lead to unnecessary anxiety or treatments that compromise quality of life without assuring a longer life than a man ignorant of his condition would enjoy.

Treatment

For most patients with localized tumors, surgical removal of the prostate gland (prostatectomy) is the initial treatment, despite possible side effects of urinary incontinence and impotence. Localized prostate cancer can often be cured. 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. Very small cancers or slow-growing cancers in older men are sometimes watched, but not treated, without compromising life expectancy. Experimental treatments under investigation include cryosurgery, destroying the tumor by freezing.

Malignant tumour of the prostate gland. Prostate cancer commonly occurs in men over age 50. Symptoms include frequent or painful urination, blood in the urine, sexual dysfunction, swollen lymph nodes in the groin, and pain in the pelvis, hips, back, or ribs. The likelihood of developing prostate cancer doubles if there is a family history. Treatment may include surgery, radiation therapy, hormone therapy, chemotherapy, or a combination of two or more of these approaches.

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