Prostate Cancer:
Rates and Risk Factors

Prostate cancer is the most common cancer in American men accounting for 198,100 new cases or 31% of all cancers in men in 2001. It accounts for 11% of all cancer deaths in men; 31,500 deaths from prostate cancer are projected for 2001 (ACS, 2001). The number of patients diagnosed with prostate cancer is decreasing and the death rate has been declining for about 7 years. The timing of these declines coincides with the availability of PSA as a routine screening test. Because approximately 50% of patients diagnosed with these cancers develop metastatic and therefore incurable disease, prevention of cancer development is a life-saving and cost-effective health strategy. Regular examinations with digital rectal examination (DRE) and prostate-specific antigen (PSA) can detect the cancer earlier, when 90% are clinically localized.

Signs and Symptoms

A number of nonspecific symptoms can suggest prostate cancer but they may also be common to other conditions. Prompt medical attention should be sought for any of the following: weak or interrupted urine flow; inability to urinate, or difficulty starting or stopping the urine flow; the need to urinate frequently, especially at night; blood in the urine; pain or burning on urination; continual pain in lower back, pelvis, or upper thighs. Because early prostate cancer is often asymptomatic, regular screening is important.

Risk Factors

Age

Ninety-five percent of prostate cancer is diagnosed in men between 45 and 89 years of age with a median age of diagnosis of 72 years. The probability of developing prostate cancer is less than 1 in 10,000 in men aged less than 39 years, 1 in 49 for men aged 40 to 59 years, and 1 in 7 for men 60 to 79 years (ACS, 2001).

Genetic Predisposition

Prostate cancer, like other forms of cancer, exists in both sporadic and hereditary forms. Men with a father or brother affected with prostate cancer are twice as likely to develop prostate cancer as men with no affected relatives. (Steinberg, et al, 1990) Men with two or three affected first-degree relatives have a 5- to 11-fold increased risk of developing prostate cancer. (Steinberg, et al, 1990; Carter, et al, 1992)

Men with an inherited predisposition are likely to develop cancer at an early age. Up to 40% of the prostate cancers in men under the age of 55 years may be caused by an inherited genetic defect. Only 5 to 10 percent of all prostate cancer is estimated to be a result of inherited predisposition.

Investigators at Johns Hopkins have defined hereditary prostate cancer as (1) a cluster of three or more affected relatives within any nuclear family, (2) the occurrence of prostate cancer in each of three generations in the proband's paternal or maternal lineage, or (3) a cluster of two relatives affected at age 55 or less.

Race

Prostate cancer rates vary widely between ethnic groups. They are generally lowest in Asian men and higher in Scandinavian men. African American men living in the United States have higher prostate cancer rates than white men of similar education and socioeconomic classes (Baquet et al, 1991).

Dietary Fat

The idea that the risk of prostate cancer is enhanced by high fat intake has been the subject of many studies and much debate. It has been suggested that dietary patterns could alter the production of sexual hormones and affect the risk of cancer in the prostate gland. The diet of Japanese men, for example, has much less fat content than that of U.S. men; as the fat content of the Japanese diet has increased toward westernized levels, the incidence of prostate cancer in Japan has started to rise. Japanese men who move to the U.S., furthermore, carry a risk of developing prostate cancer that is intermediate between the low risk in Japan and the high risk in the U.S. (Shimizu et al, 1991)

Hormones

Clearly, hormones play an important role in normal and cancerous prostate physiology; however, their relationship to prostate cancer risk is still undefined.

Vasectomy

Several large retrospective and prospective studies have suggested that vasectomy may increase the risk of prostate cancer 1.2-fold to 2-fold, especially if vasectomy was performed at a young age(<35 years old) (Giovannucci et al, 1993a, 1993b; Hayes et al., 1993). These findings, however, have been vigorously debated. If vasectomy is associated with an increased risk of prostate cancer, the risk appears to be low.

Screening Strategies

Prostate cancer screening has continued to grow in popularity, fueled by the belief that early detection through DRE or PSA leads to the identification of organ-confined, curable tumors (Scardino, 1989). To date, no trial has been completed to determine whether screening for prostate cancer saves lives. The National Cancer Institute is in the midst of the large-scale Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial to determine if certain tests will reduce the number of deaths from these cancers. Some 37,000 men ages 55 to 74 are being screened to determine if these men are less like to die of prostate cancer than men who have not been screened. The trial will also assess how well PSA levels correspond to the presence and size of a tumor. Eventually, data from such trials and screening programs such as Prostate Cancer Awareness Week should identify the utility and value of prostate cancer screening programs. Currently the American Cancer Society and the American Urological Association recommend DRE and a PSA blood test annually starting at age 50. Screening for men at increased risk for prostate cancer (African American men and men who have a father or brother with prostate cancer diagnosed at a young age) should begin by age 45 or 10 years earlier than the youngest age of a family member with prostate cancer.

Sharon Olsen, MS, RN

Janet Walzak, MSN, CRNP