Prostate Cancer Detection

Prostate cancer can grow quietly for years, which means most men with the disease have no obvious symptoms. Until more is known, the decision about whether or not a man should be tested for prostate cancer should be left up to the patient and his doctor after they discuss the pros and cons of testing. The American Cancer Society recommends that doctors offer the PSA blood test and digital rectal exam to men who have at least a 10-year life expectancy beginning at age 50, and to younger men who are at high risk.

Signs and Symptoms of Prostate Cancer

When symptoms finally appear, they often are similar to those caused by prostate enlargement: difficulty urinating; a weak stream; a frequent urge to urinate, especially during the night; painful or burning urination; blood in the urine.

When cancer grows through the prostate capsule, it invades nearby tissues. It also may spread to the lymph nodes of the pelvis, or it may spread throughout the body (metastasize) via the bloodstream or the lymphatic system. Prostate cancer tends to metastasize to the bone. As a result, bone pain, particularly in the back, can be another symptom of prostate cancer.

Clinical Exams

Screening

Some doctors recommend screening for prostate cancer. Screening, distinct from diagnosis, looks for signs of disease in people who have no cancer symptoms.

Screening for prostate cancer is controversial, because it is not yet known if the process actually saves lives, and it is not always clear that benefits outweigh the risks of diagnostic tests and treatments.

The main screening tools for prostate cancer are the Digital Rectal Exam (DRE) and the Prostate-Specific Antigen (PSA) test. The higher a man?s PSA level, the more likely that cancer could be in the picture. During screenings in men ages 50 or older, 85 of every 100 men will have normal PSA levels (4 ng/ml or below). Among the remaining 15 men, only 3 will have biopsies that show cancer.

Neither PSA nor DRE accurately identifies all cancers. The PSA is more accurate than the DRE, but it still misses about one-third of cancers that are clinically localized (appear not to have grown through the prostate capsule).

In spite of possible inaccuracy, most tumors that are found through screening are indeed early cancers.

Still, it is troublesome that PSA and DRE can falsely suggest cancer where none exists. Most men with an elevated PSA (or an abnormal DRE) go on to have additional diagnostic tests. Yet the majority of these men do not have cancer and will suffer needless anxiety.

Some recent refinements designed to make PSA testing more accurate and more precise are under clinical study. For instance, PSA density relates a man?s PSA level to the size of his prostate, which can be estimated through ultrasound. PSA velocity is based on changes in PSA levels over time; a sharp rise from a baseline level raises the suspicion of cancer.

PSA circulates in the blood in two forms: free or attached to a protein molecule. In the case of a benign enlargement, there is more free PSA, while cancer produces more of the attached form, although the reasons for this difference are not well understood.

As for DRE, this test is most accurate when performed by a doctor who is highly skilled in such a procedure. But the procedure does have problems, often missing many small cancers, especially cancers toward the front of the prostate gland or deep within it. The exam also is notoriously unpopular among men and even among some doctors. Many men say they find the test embarrassing an uncomfortable. Studies also suggest that some physicians are reluctant to do rectal exams.

Digital Rectal Examination (DRE)

The standard technique for evaluating the health of the prostate is by physical examination called a digital rectal examination (DRE). Typically, a patient is asked to bend forward over a table while the doctor inserts a gloved and lubricated finger (called a digit in the medical community) into the patient?s rectum. This allows the physician to feel the back portion of the prostate gland. In addition to gauging the gland?s size, the doctor is able to evaluate its firmness and texture. The doctor looks for answers to some key questions: Has its usually rubbery feel changed? Are there any hard areas or lumps, which could signal a cancer? Has a growth spread beyond the prostate?

Prostate-Specific Antigen (PSA)

This is a substance produced by cells of the prostate gland. PSA circulates in the blood and can be detected and measured with a relatively simple blood test. When the gland enlarges, PSA levels rise. PSA levels can also rise if cancer develops.

However, many factors can influence PSA levels. Some prostate glands naturally produce more PSA than others. PSA scores also tend to increase with age. Another influence on PSA levels is race: PSA levels tend to be higher in African-Americans, and lower among Japanese, than in white Americans.

A variety of conditions can raise PSA levels temporarily. These include prostatitis, prostate biopsy and transurethral prostate surgery.

Transrectal Ultrasound (TRUS)

This procedure uses a small probe that is inserted into the rectum. The probe emits and picks up high-frequency sound waves. The sound waves bounce off the prostate, producing a pattern that is converted into a video image. Areas of cancer produce a different pattern than healthy tissue. The value of a TRUS is strongly influenced by the quality of the equipment and the skill of the person operating it.

While ultrasound does not provide enough specific information to make it a good screening tool by itself, doctors find it useful as a follow-up to a suspicious DRE or PSA. TRUS is also used to guide biopsies in sampling abnormal areas of the prostate, to estimate the volume of the prostate for calculating PSA density, and to situate radiotherapy implants.

Biopsy

Like other cancers, prostate cancer can actually be diagnosed only by examining tissue under a microscope. Whenever cancer is suspected, the diagnosis must be confirmed by a biopsy.

If your symptoms, the DRE, or your PSA test suggest cancer, your doctor will refer you to a urologist for a biopsy. The biopsy is typically performed in the urologist?s office. The urologist obtains an image of the prostate through a transrectal ultrasound probe. Then, to obtain tissue samples, the doctor inserts thin biopsy needles into areas of the gland that feel or look suspicious. Bits of tissue are removed from each site through the hollow needles. Each snip causes a sharp sting.

The tissue samples are then turned over to a pathologist, a doctor who specializes in the study of the microscopic cell and tissue changes produced by disease.

When a biopsy is prompted by an elevated PSA, rather than an abnormal area in the prostate gland detected by a rectal exam, the urologist may take random samples from six or more prostate areas. In a so-called pattern biopsy, the tissue samples are obtained from carefully spaced sectors of the gland. This helps establish the size and extent of any cancer.

Most men who have biopsies are following routine exams do not have cancer. About three-quarters of the biopsies are triggered by an abnormal DRE, and more than four-fifths of those instigated by an elevated PSA reveal no cancer.

You should talk with your physician about the biopsy results. If there is any doubt about the diagnosis, you can get a second opinion from another pathologist.

Biopsies can miss cancer, too, about one-fifth of the time. If your doctor strongly suspects cancer on clinical grounds, but the biopsy was negative, he or she may recommend a second biopsy.