Sexual Activity and Prostate Risks

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Some reports in the media have suggested that sexual activity increases the risk of prostate cancer. "The evidence, however, is still far from conclusive," says Carmen Rodriguez, MD, MPH, senior epidemiologist and director of the Lifelink Blood Collection Study for the ACS. Dr. Rodriguez believes that there is no consistency in the research. "It is an interesting and possible real association," Rodriguez notes, "but not an established risk factor."

According to the American Cancer Society (ACS), approximately one out of every ten men will develop prostate cancer during his lifetime. Nearly 200,000 men will be diagnosed with it this year, making it the second most common cancer in males after lung cancer. Although prostate cancer causes more than 41,000 deaths annually, men are living longer with the disease than ever before due to early screening and many effective treatments.

The prostate is a male sex gland that is located between the bladder and the rectum. Normally it is about an inch and a half in diameter and somewhat elongated into the shape of a small upside down pear. The prostate gland manufactures prostatic fluid which, in turn, regulates the acidity of semen. It also wraps completely around the urethra, the tube that empties urine from the bladder through the penis. It is connected to the male reproductive organs as well.

In spite of the fact that the cause of prostate cancer is unknown, researchers have long theorized that there may be a relationship between sexual activity including sexually transmitted diseases and the risk of developing prostate cancer. Scientists already know that women who have unprotected sex risk catching a sexually transmitted disease called the human papilloma virus, which causes virtually all cases of cervical cancer.

The Most Recent Study

Karin Rosenblatt, a professor of community health at the University of Illinois at Urbana-Champaign, and Janet Stanford and Kristine Wicklund, researchers in the Program in Epidemiology at the Fred Hutchinson Cancer Research Center in Seattle, conducted a study which found that sex with multiple partners and the associated exposure to sexually transmitted diseases may raise a man's odds of getting prostate cancer in middle age. Their findings were published in the June 15, 2001 issue of the American Journal of Epidemiology (vol. 153, no. 12:1152-1158).

The study was based on interviews with 1,456 men aged 40-64 in King County, WA. The study group consisted of 753 men who had been diagnosed with prostate cancer between 1993 and 1996. They were identified by the Seattle-Puget Sound cancer registry, part of the National Cancer Institutes' Surveillance, Epidemiology and End Results (SEER) Program. The control group of 703 men was chosen using random-digit telephone dialing, with an age distribution similar to that of the study group. The subjects provided information regarding sexual behavior, medical history and other prostate cancer risk factors. Rosenblatt and her colleague's results indicated that the risk of prostate cancer increased directly with the lifetime number of female sexual partners, but not with male partners. Men who had 30 or more sexual partners appeared to be twice as likely to develop prostate cancer during middle age than men who had fewer sexual partners. Just 16 percent of the prostate cancer sufferers had one lifetime sex partner, compared with 22 percent of the healthy men. Seventeen percent of the ill men had more than 30 sex partners, compared with 13 percent of the healthy men.

Their results also suggested that a sexually transmitted infection might play a part in the development of the disease. Prior infection with gonorrhea was positively associated with risk, but no effect was seen among men with other sexually transmitted diseases. They also found no relationship between prostate cancer and frequency of intercourse. In fact, some doctors say that regular sex can actually be important in the prevention of prostate cancer because it cleanses the prostate gland. William Catalona, director of the Division of Urologic Surgery at the Washington University School of Medicine in St. Louis, MO, adds, "There's no hard data to prove this." It is not uncommon, however, for Dr. Catalona, a urologist, to see a patient develop a flare-up of prostatitis (inflammation of the prostate) after not having regular sex for a while.

In their book Prostate Cancer: What Every Man and His Family Needs to Know (Villard Books, revised 1999) the ACS states, "Since the prostate produces part of the seminal fluid, some people theorize that not having frequent regular orgasms to expel the fluid can cause it to 'back up' inside the gland, leading to prostate cancer. This is false. For one thing, semen does not accumulate. The body produces the amount it needs and holds onto it for a while. If it is not ejaculated within a certain period of time, it is reabsorbed by the body and a fresh supply is produced."

Further Study Needed

Although the Rosenblatt study suggests that an active sexual life may increase the risk for prostate cancer, many studies refute this possibility. "One study found that the risk for Catholic priests was no lower than in sexually active men," says Dr. Catalona. Even Rosenblatt herself points out that though the numbers were cause for concern, they should not be overplayed. In a University of Illinois press release announcing the study she stated, "I'm not sure we've figured out the mechanism with this. Some studies don't show any association and some studies do, so I think there needs to be a little more research in this area." The numbers may certainly be valid, but there is no clear cause and effect.

The study, titled "Sexual Factors and the Risk of Prostate Cancer," was conducted by the Fred Hutchinson Cancer Research Center and was supported by a grant from the National Cancer Institute.

For a summary of what is known about prostate risks so far, read about ACSH's new report: http://www.acsh.org/publications/booklets/prostate2002.html