Diagnosing Prostate Cancer
Advanced Screening Tools Lead to Accurate Diagnosis
Fox Chase uses the most advanced screening tools to diagnose prostate cancer as accurately as possible.
Most prostate cancers are diagnosed after screening tests with a digital rectal exam (DRE) or a prostate-specific antigen (PSA) test.
Some prostate cancers may be found because of symptoms, such as slowing or weakening of the urinary stream or the need to urinate more often. These symptoms can also be caused by benign prostatic hyperplasia (BPH), or enlarged prostate. Most early prostate cancers cause no symptoms and are found early by screening tests.
Primary Prostate Cancer Screening Tools:
Digital Rectal Exam (DRE)
The simplest and oldest screening test for prostate cancer is the digital rectal exam, or DRE. A doctor gently inserts a gloved forefinger into the rectum to feel the prostate gland for enlargement or other obvious abnormalities, such as a lump. The DRE is not a definitive cancer test, but regular exams help the doctor detect any changes in the prostate. A DRE should be done along with a PSA test.
Prostate-specific antigen, or PSA, is a protein produced by the cells of the prostate gland. This prostate cancer blood test measures the amount of PSA circulating in the blood. The results are shown in nanograms per milliliter (ng/ml), but are most commonly referred to by the ng/ml number. The PSA level is used to determine what additional tests may be needed. Non-cancer reasons for an elevated PSA include, but are not limited to, prostate enlargement, inflammation and infection. If the PSA is mildly elevated, your doctor may obtain a "percentage-free PSA."
The PSA test is not 100% effective in diagnosing prostate cancer due to the high number of false positive (a high PSA level exists when cancer doesn't) and false negative (a low PSA level exists though cancer is present) results. However, it is the best tool at this time for diagnosing prostate cancer. By looking at changes in PSA levels over time, doctors can overcome some of these inadequacies.
Other Tools Used To Diagnose Prostate Cancer:
"Percentage-free PSA Test"
PSA circulates in the blood stream either attached to a carrier (bound) or not attached to a carrier (free PSA). Until several years ago, the laboratory could only detect the combination of bound and free PSA, or the "total PSA." The common PSA test used today measures the "total PSA."
Newer laboratory techniques allow for the detection of the "free" PSA. Percentage-free PSA measures the aggressiveness level of a cancer. The lower the percentage of free PSA, the more aggressive the cancer is likely to be--important information to know when planning treatment.
The percentage-free PSA is determined mathematically by dividing the free PSA number by the total PSA number. The lower the percentage-free PSA, the higher the risk of having cancer. Biopsies are not recommended for men with percentage-free PSA values above 25% (unless medical factors are involved).
Prostate Biopsy and Transrectal Ultrasound (TRUS)
A biopsy, or sampling of prostate tissue, is the only way early prostate cancer can be pathologically confirmed without surgically removing the prostate A diagnostic radiologist with expertise in prostate biopsies performs this outpatient procedure, after local anesthesia has been administered. A biopsy is performed on men with a strong suspicion of cancer based on PSA and DRE test results and other factors. During the biopsy, a specialized ultrasound probe is placed in the rectum, called a transrectal ultrasound (TRUS). This allows the radiologist to see the prostate. Often, the prostate cancer looks similar to normal tissue, so at least 10 samples are taken from the area of the gland where tumors are typically found. These samples are sent to pathology for accurate diagnosis.
In addition to guiding the biopsy needles, transrectal ultrasound, or TRUS, is used to gather additional information about the prostate. TRUS uses sound waves to create a video image of the prostate gland. The probe releases sound waves, which create echoes as they enter the prostate. Prostate tumors sometimes create echoes that are different from normal prostate tissue. The echoes that bounce back are sent to a computer that translates the pattern of echoes into a picture of the prostate. TRUS alone cannot detect every tumor, but it has been shown to detect some tumors that cannot be felt by a DRE. TRUS can also estimate the size of the prostate gland, helping doctors get a better idea of PSA "density," which helps distinguish benign prostatic hyperplasia (BPH) from prostate cancer.
Gleason Grading System After a Biopsy
After a biopsy has been performed, the tissue is sent to a pathologist for further study. An accurate diagnosis is critical. Pathologists at Fox Chase have extensive experience in diagnosing prostate cancers, especially in early disease when benign tumors can be mistaken for cancer and vice versa. Prostate cancers contain several patterns of cells that appear differently under a microscope. The Gleason grading system uses the numbers 1-5 to "grade" the most common (primary) and next most common (secondary) cell types found in a tissue sample. Together, the sum of these two numbers is the Gleason score, ranging from 2-10. This tells the physician how aggressive the tumor appears under the microscope. A higher Gleason score represents a more aggressive cancer. Doctors consider Gleason score, PSA level and the volume (amount of cancerous tissue detected within the core of the biopsy) of cancer in order to assess the potential aggressiveness of the cancer and assist in treatment options.
Topics in This Section
Should men with prostate cancer receive DEXA screening?by Mary B. Daly, MD, PhD, FACP
March 20, 2013
A report says less than 15 percent of men on androgen-deprivation therapy (ADT) are being screened.
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Cancer Conversations »
Prostate Cancer: Is PSA Screening Worth the Trouble?by Marc Smaldone, MD
November 14, 2012
As with most differences in opinion, the truth lies somewhere in-between.
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Cancer Conversations »
For men who have a family history or other risk factors for prostate cancer. Learn more »
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