Prostate Health

Prostate Cancer and the PSA Tests
by Food and Drug Administration (FDA)

(Page 4 of 4)

The third major problem that can occur in the prostate is cancer. It grows quietly for years, giving most men with the early disease no obvious symptoms.

"It's a silent killer," says J. Brantley Thrasher, M.D., chairman of urology at the University of Kansas Medical Center in Kansas City, Kan., and spokesman for the American Urological Association (AUA). "So, most men with a nodule or elevated PSA aren't going to know it." That's why Thrasher and the AUA believe strongly in PSA testing. "It's an imperfect marker, but it's the best we've got."

The FDA approved the PSA test for use in conjunction with a DRE to help detect prostate cancer in men 50 and older, and for monitoring prostate cancer patients after treatment. According to scientists in the FDA's Center for Devices and Radiological Health (CDRH), the finger examination can detect cancer in the form of a nodule or hardness, normally when it is about 50 percent advanced and not curable. PSA detects cancer when the finger exam appears normal in about 35 percent to 40 percent of cases, in the early stages of disease.

Indeed, the NCI and the ACS agree that checking people for some cancers, such as breast and colon, even when they have no symptoms, can reduce deaths by finding tumors at an early stage, when they are easiest to treat. But when it comes to prostate cancer, the argument isn't so clear-cut.

"Prostate cancer is generally a slow-growing cancer," says Cmdr. James P. Reeves, Ph.D., a medical device reviewer in the FDA's CDRH. "For those men who do not have slow-growing cancer that will threaten their lives, we do not have sufficient information that PSA or DRE testing prior to or after diagnosis would distinguish such men from those who will have cancer, but will not die from that cancer."

So what's the harm in being tested? Reeves says that screening for prostate cancer sometimes finds tumors that wouldn't cause any problems if left untreated. Many professional medical organizations agree. But there's no good way at this time to tell which cancers need treating and which don't. Therefore, many men who are diagnosed with prostate cancer likely will be treated, but also may experience unnecessary and harmful side effects that could lower their quality of life. About 15 percent to 50 percent of men treated for prostate cancer by surgery, radiation therapy, or hormonal therapy will have urinary incontinence and sexual impotence, and in extremely rare cases, scarring of the intestine.

"These percentages indicate that there is a risk for significant harm from over-treatment of prostate cancer," Reeves says. "Is the cure worse than the disease, especially if the cancer is not significant enough to threaten a man's life over 10 to 15 years of remaining life expectancy?"

There are some men who have ample reason to choose the cure. "My grandfather and my father had prostate cancer," says 54-year-old David Glunt from St. Louis. "And at 51 years old, I wasn't taking any chances." Glunt's younger brother tested positive for prostate cancer four years ago; Glunt tested negative. "But I was betting all along that I would get it," he says. A year later, he did.

Speaking on behalf of the AUA, Thrasher says that while a more specific and sensitive marker is needed, questioning the validity of early screening puts men at risk. "Physicians should discuss the risks and benefits of prostate cancer screening on a yearly basis with men 50 to 75 years of age, and earlier if they are African-American or have a family history of prostate cancer," Thrasher says. Screening, he adds, should include both a PSA test and DRE.

Because so much remains unknown about how to interpret the PSA test, its ability to discriminate between cancer and noncancerous conditions, and the best course of action if the PSA is high, the magnitude of the test's potential risks and benefits also is unknown.

Still, Kibel adds, "the PSA controversy should not stop men from discussing being tested with their doctors."

In its early stages, prostate cancer stays in the prostate and is not life-threatening. But without treatment, cancer eventually spreads to other parts of the body, often resulting in death.

Doctors have several ways to treat prostate cancer. The choice depends on many factors, such as whether or not the cancer has spread beyond the prostate, the patient's age and general health, and how the patient feels about the treatment options and their side effects. According to both the NCI and the ACS, approaches to treatment include: watchful waiting to see whether the cancer is growing slowly and not causing symptoms; surgery to remove the entire prostate and surrounding tissues; and internal and external radiation therapy, both of which use high-energy rays to kill cancer cells and shrink tumors. Hormone therapy and chemotherapy drugs are approved to treat the various advanced stages of cancer.

The gold standard for treating early, localized prostate cancer is radical retropubic prostatectomy. The whole prostate and seminal vesicles are removed. At Johns Hopkins Hospital in Baltimore, the surgery has improved over the years with the development of a nerve-sparing procedure. This procedure, says the CDRH, in most cases, avoids sexual impotence. The same technique has been used in the last decade by many urologists in the United States and throughout the world.

Computer- or robot-assisted surgery was cleared by the FDA in 2005 for use in all urological procedures, including the removal of the prostate (radical prostatectomy) because of cancer. Even though the prostate is surrounded by nerves and muscles that affect urinary, rectal, and sexual functions, doctors say that improved vision and flexibility of the instruments allow for magnification of the prostate during this procedure. "It's too early to tell if this will equate to more precision and better outcomes," adds Thrasher.

Regular checkups are important even for men who have had surgery. BPH surgery does not protect a man against prostate cancer, because the prostate is not completely removed.

Research is under way to evaluate new approaches to finding even more effective treatments for prostate and urinary disorders.

The Science Behind Prostate Specific Antigen

Prostate specific antigen (PSA) is a substance made by the prostate gland. Although the substance is mostly found in semen, a small amount is also present in the blood. According to the American Cancer Society, most men have levels under 4 nanograms per milliliter of blood (ng/ml). When prostate cancer develops, the PSA level usually goes above 4ng/ml but in some cases, the cancer can be present at levels lower than 4. A PSA rise does not automatically mean cancer. PSA also rises when the prostate is enlarged because of benign prostatic hyperplasia, or BPH, and sometimes with prostatitis.

If the level is borderline range between 4ng/ml and 10ng/ml, a man has about a 25 percent to 35 percent chance of having prostate cancer. PSA higher than 10ng/ml could mean between a 40 percent and 50 percent chance for cancer, and the risk increases further as the PSA level increases. PSA is an ideal marker for prostate cancer because it is basically restricted to prostate cells.

Most PSA tests measure "total PSA," or the amount that is bound to blood proteins. But some tests measure not only total PSA, but another component called free PSA, which floats unbound in the blood. Free PSA above 25 percent is a stronger indication that cancer is not present. Comparing the two helps doctors rule out cancer in men whose PSA is mildly elevated from other causes.

The benefits of screening for prostate cancer are still being studied. Scientists are researching ways to distinguish between cancerous and noncancerous conditions, those that are slow-growing and fast-growing, and potentially lethal cancers through new PSA methods and other tumor markers.

The National Cancer Insitute and other medical organizations are conducting the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, or PLCO Trial, to determine whether certain screening tests reduce the number of deaths from these cancers. The PSA and DRE tests are being studied to see whether yearly screening will decrease a man's chance of dying from prostate cancer.

About the Author

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