Prostate Cancer

Prostate Cancer

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Prostate Cancer, malignancy of the prostate gland, a walnut-sized organ located under the bladder in males. The prostate gland surrounds the urethra, which is the tube that carries urine from the bladder to the penis. The American Cancer Society estimates that about 180,000 new cases of prostate cancer are diagnosed annually in the United States and that about 32,000 men die from the disease each year. According to the Canadian Cancer Society, each year prostate cancer is diagnosed in about 16,900 men in Canada and about 4,200 die from the disease. Prostate cancer is the second leading cause of cancer death, after lung cancer, in men living in the United States and Canada.


RISK FACTORS

The specific mechanisms that lead to the development of prostate cancer are still unknown, but several risk factors for the disease have been identified. Incidence increases with age—prostate cancer seldom develops before the age of 40 and is chiefly a disease found in men over the age of 65. It is most common in North America and in northwestern Europe but rare in South America, the Near East, and Africa. In the United States, black males, who suffer from the disease 37 percent more often than white males, have the world’s highest incidence. A growing body of evidence links diets rich in animal fats with prostate cancer. Dietary differences are believed to explain why the incidence of prostate cancer is 120 times greater in the United States than in China, where fatty foods are not part of the general diet.

Some foods seem to act as a shield against this disease. Studies show that tomato-based products protect against prostate cancer, possibly because tomatoes are rich in a substance called lycopene. Lycopene is an antioxidant, a chemical agent that inhibits or retards the cellular process of oxidation. Too much cellular oxidation can be dangerous to a person’s health because it produces molecules called free radicals that increase the risk of cancer developing in body tissues. Long-term, moderate doses of vitamin E, another type of antioxidant, may block the progress of prostate tumors.

Environmental factors, such as workplace exposures to cadmium, have also been associated with increased risk of prostate cancer. Family history plays another important role. Men whose fathers or brothers develop prostate cancer are more likely to develop the disease. Researchers are beginning to identify genetic markers of prostate cancer. For instance, the gene known as hereditary prostate cancer 1 (HPC1) appears to significantly predispose men to prostate cancer when inherited in a mutated form.


SYMPTOMS AND DIAGNOSIS

Prostate cancer usually progresses slowly and produces no symptoms in its initial stages. Warning signs may eventually include difficult or painful urination; frequent urination, especially at night; and blood in the urine or semen. Pain in the lower back, pelvis, or upper thighs may signal that prostate cancer cells have spread to the ribs, pelvis, and other bones. All these symptoms, however, may have other causes, such as infection and prostate enlargement, which are a natural result of the aging process.

Many doctors perform screening tests for prostate cancer during regular physical exams in order to identify the disease in its earliest—and most curable—stages. Doctors perform a digital rectal examination, in which the physician uses a gloved finger to gently check the smoothness of the rectal lining. If cancer is present, a physician may feel a nodule or other prostate irregularity. Another screening test, called the prostate-specific antigen (PSA) test, measures levels of a protein called prostate-specific antigen in the blood. Prostate cancer cells overproduce this protein, causing an elevation of PSA levels in blood. If screening tests indicate cancer is present, a physician will usually perform a biopsy, in which a tissue sample is removed from the prostate and examined under a microscope. The American Cancer Society recommends that men aged 50 years and older should have an annual digital rectal exam and PSA test. Men who have a high risk for the disease (blacks or those with a family history of prostate cancer) should talk to their doctors about starting annual screening tests at a younger age.