PSA: How a Simple Blood Test Can Detect Prostate Cancer

What Is Prostate-Specific Antigen?

Antigens are special markers produced by most types of cells. They are found in viruses, bacteria, parasites, tumors, and even on healthy cells in the body. They are typically made of proteins or sugars and are unique to the type of cell or substance that produces them.

The immune system uses antigens as a type of marker to identify which substances are threats and which are not. When the immune system recognizes an antigen that belongs in the body, called a “self” antigen, it knows to leave the related cells alone. When it detects an unfamiliar or “non-self” antigen, however, it attacks to destroy the intruder cells.

Prostate-specific antigen (PSA) is produced by cells in the prostate gland. While both normal and cancerous prostate cells produce PSA, cancerous cells often produce more. This causes PSA levels to rise when cancer is present, making PSA screening an effective way to recognize the potential presence of cancer.

What Is PSA Screening?

PSA screening is performed by measuring the amount of PSA present in a sample of blood. Doctors look at blood levels of PSA both to identify potential cancers (PSA screening) and to assess the status of men already diagnosed with prostate cancer (PSA monitoring).

PSA screening cannot detect all forms of prostate cancer because some cancers do not raise PSA levels. It may also return false positives if PSA levels have been impacted by factors unrelated to cancer. In general, however, the blood test is a useful tool for detecting cancer or monitoring its progress. Best of all, the test takes only minutes to complete, making it one of the most convenient ways to check for cancer.

What to Expect From PSA Screening

When a patient arrives for PSA screening, a phlebotomy technician will begin by selecting a blood draw site, typically on the patient’s arm. The site will be cleaned with a disinfectant before the technician takes a blood sample. The draw is usually quick and painless, though the patient may feel a slight sting as the needle enters and leaves their arm. Any bleeding is blotted with a cotton swab before a bandage is placed over the draw site.

As with any other blood draw, patients are advised to rest briefly after testing and to drink plenty of liquids. The sample will be sent to a medical laboratory to be tested by a pathologist. Lab results will be returned within a few days or weeks, at which point a follow-up appointment may be scheduled to discuss the results and the next steps.

Understanding PSA Screening Results

The PSA level is measured in units called nanograms per milliliter (ng/mL). Higher levels indicate a higher chance of cancer. In general, most men without prostate cancer have PSA levels below four ng/mL. If the PSA level is between four and 10 ng/mL, the patient has a one in four, or 25%, chance of having cancer. If the PSA level is above 10 ng/mL, the chances of cancer rise to 50%.

Although higher PSA levels indicate a higher likelihood of prostate cancer, PSA screening results cannot detect the presence of cancer with absolute certainty. Some cancer types do not affect PSA levels in a significant way. In addition, PSA levels vary between individuals, and there is no concrete threshold that distinguishes between normal and abnormal results. Further, PSA levels may be affected by a variety of factors and conditions unrelated to cancer, including:

• Age
• Vigorous exercise
• Sexual activity
• Prostate infections
• Recent biopsies
• Benign prostate hyperplasia (BPH)
• Use of certain drugs that treat BPH
• Use of certain herbal supplements

As a result, a high PSA reading should not be taken as a sure sign of cancer. Instead, men with elevated levels of PSA should pursue further testing. This will determine the cause of elevated PSA levels, helping the patient make a fully informed decision regarding treatment.

Next Steps After Screening

If elevated PSA levels are detected on a screening test, the patient and his healthcare provider will discuss the next steps. This typically involves further testing to confirm the results of the PSA test and to determine what has caused the elevated reading. The typical screening-to-diagnosis process for prostate cancer is as follows:

Follow-Up PSA Test

The first step after detecting an abnormal PSA level is often to schedule a follow-up test, particularly if the patient has no symptoms that would suggest prostate cancer and does not have a strong family history of the disease. The follow-up test may be performed six weeks or more after the original test. The time gap helps physicians determine whether the elevated reading was temporary, and thus likely caused by transient factors, or whether the patient’s PSA level is consistently elevated.

Digital Rectal Exam

A doctor may also perform a digital rectal exam (DRE) as part of the initial follow-up of an elevated PSA level. During this test, the doctor inserts a gloved finger into the rectum to feel for abnormalities. The test may detect a lump, indicating a tumor. If the DRE does not detect a lump, subsequent PSA tests and DREs may be performed over time to monitor the patient’s condition and ensure that no cancer develops.

Imaging

If the PSA level is elevated on repeat testing, if a lump is detected during the DRE, or if the physician has other cause for concern, an imaging test may be ordered to look for a tumor. Common imaging tests used for prostate cancer detection include magnetic resonance imaging (MRI), which uses radio waves and strong magnets to create an image, and transrectal ultrasound (TRUS), which employs sound waves to form an image of the prostate and surrounding anatomy

Biopsy

A biopsy is critical for determining the presence of prostate cancer and providing key information on the nature and extent of the disease. This test involves taking a sample of tissue from the prostate. To perform the biopsy, a doctor inserts a thin, hollow needle through the wall of the rectum or through the skin between the anus and the scrotum to remove a small amount of prostate gland tissue. The physician will take several biopsies – usually around 12 – in rapid succession so that pathologists can check different areas of the prostate for cancerous cells.

While the idea of having a biopsy may be daunting, each sample taken typically causes only brief discomfort, and doctors often inject a local anesthetic prior to the biopsy to numb the area. The entire procedure typically takes roughly 10 minutes. Patients often are given an antibiotic both before the biopsy and for a couple of days afterward to reduce the risk of infection. The samples taken are then sent to the laboratory for evaluation. If those samples do show the presence of cancer, pathologists then perform further testing to assess key characteristics of the disease that can influence decisions about which type of treatment is most appropriate.

Receive Prostate Cancer Care at an RCCA Location Near You

If you have been diagnosed with prostate cancer, look to the expert medical oncologists of RCCA for comprehensive, compassionate care. RCCA offers the latest prostate cancer therapies at more than 20 locations in New Jersey, Connecticut, Massachusetts, Maryland, and the Washington, D.C., area. Our specialists have extensive experience in diagnosing and treating a wide variety of cancers and blood disorders. Contact us to learn more or request an appointment.