Prostate cancer

Prostate cancer is a group of cancerous cells (a malignant tumor) that begins most often in the outer part of the prostate. It is the second most common type of cancer in men in the United States. Skin cancer is the most common. Of all the men who are diagnosed with cancer each year, more than one-fourth have prostate cancer.

Causes

Although researchers know several risk factors for prostate cancer, they still are not sure why one man develops the disease and another doesn't. (Known risk factors, which include aging, are listed in the "Prostate Cancer: Who's at Risk?" section.)

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Some aspects of a man's lifestyle may affect his chances of developing prostate cancer. For example, some evidence suggests a link between diet and this disease. These studies show that prostate cancer is more common in populations that consume a high-fat diet (particularly animal fat), and in populations that have diets lacking certain nutrients. Although it is not known whether a diet low in fat will prevent prostate cancer, a low-fat diet may have many other health benefits.

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There are large differences in prostate cancer risk between racial groups, but it is not yet clear why this is so. African Americans have the highest incidence of prostate cancer in the world.

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Researchers are interested in genes that may influence the risk of developing prostate cancer. They are studying the genes of men who were diagnosed with prostate cancer at a relatively young age (less than 55 years old) and the genes of families who have several members with the disease. Much more work is needed, however, before scientists can say exactly how changes in these genes are related to prostate cancer. Men with a family history of prostate cancer who are concerned about an inherited risk for this disease may be interested in talking to a genetic counsellor. However, there are, as yet, few identified genes that are known to affect prostate cancer risk.

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Prevention

Several studies are under way to explore how prostate cancer might be prevented. These include the use of dietary supplements, such as vitamin E and selenium. In addition, recent studies suggest that a diet that regularly includes tomato-based foods may help protect men from prostate cancer.

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The drug finasteride was studied in the Prostate Cancer Prevention Trial. This drug is used to treat hair loss. It functions by blocking the conversion of testosterone to dihydrotestosterone. Thousands of men across the country participated in the study for 7 years. The results of the study are a key finding in prostate cancer research, especially because of its findings about the prevalence of prostate cancer among men with supposedly 'normal' PSA results.

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Scientists are also looking at ways to prevent recurrence among men who have been treated for prostate cancer. These approaches involve the use of drugs such as finasteride, flutamide, and LH-RH agonists. Studies have shown that hormonal therapy after radiation therapy or after radical prostatectomy can benefit certain men whose cancer has spread to nearby tissues.

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Researchers also are investigating whether diets that are low in fat and high in soy, fruits, vegetables, and other food products might prevent a recurrence. For example, the Adventist Health Study found that meat-eaters had a 54% increased risk for prostate cancer when compared with vegetarians, even after adjusting for age, sex, and smoking (source: American Dietetic Association. 2003. Position paper on vegetarian diets. J Am Diet Assoc, 103, 748-765). The Cancer Information Service can provide information about these studies.

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In July, 2003, an Australian research team lead Graham Giles of The Cancer Council released a report of a medical study that concluded that frequent masturbation by males may be an effective preventative measure. It was speculated by the researchers that the resulting ejaculations helps remove carcinogens from the gland area. http://story.news.yahoo.com/news?tmpl=story&u=/nm/20030716/ts_nm/health_masturbation_dc_6 A subsequent study from the Health Professionals Study found no link between the two http://jama.ama-assn.org/cgi/content/abstract/291/13/1578?etoc.

Related Topics:
2003 - Australia - Masturbation - Ejaculation

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Due to old and limited studies, it was thought that increased levels of sexual activity led to an increased risk of prostate cancer. The results of a much larger study published in The Journal of the American Medical Association seem to suggest the opposite, however. Culminating in 2004, the study found that men who ejaculated (through sexual activity or masturbation) 21 times or more a month had decreased levels of occurrence. This was true across all age groups.

Related Topics:
The Journal of the American Medical Association - 2004 - Masturbation

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Screening/Early detection

Researchers are studying ways to screen men for prostate cancer (check for the disease in men who have no symptoms). At this time, it is not known whether screening for prostate cancer actually saves lives, even if the disease is found at an earlier stage. The NCI-supported Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial is designed to show whether certain detection tests can reduce the number of deaths from these cancers. This trial is looking at the usefulness of prostate cancer screening by performing a digital rectal exam and checking the PSA level in the blood in men ages 55 to 74. The results of this trial may change the way men are screened for prostate cancer. The Cancer Information Service can provide information about this trial.

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Treatment

Many studies of new approaches for men with prostate cancer take the form of phase III clinical trials.

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Cryosurgery is under study as an alternative to surgery and radiation therapy. The doctor tries to avoid damaging healthy tissue by placing an instrument known as a cryoprobe in direct contact with the tumor to freeze it. The extreme cold destroys the cancer cells.

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Doctors are studying new ways of using radiation therapy and hormonal therapy. They also are testing the effectiveness of chemotherapy and biological therapy for men whose cancer does not respond or stops responding to hormonal therapy. In addition, scientists are exploring new treatment schedules and new ways of combining various types of treatment. For example, they are studying the usefulness of hormonal therapy before primary therapy (surgery or radiation) to shrink the tumor.

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For men with early stage prostate cancer, researchers also are comparing treatment with watchful waiting. The results of this work will help doctors know whether to treat early stage prostate cancer immediately or only later on, if symptoms occur or worsen.

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