How is an Examination (Digital Rectal Exam/DRE) performed:
The digital rectal exam is the simplest way to detect physical abnormalities in the prostate gland that may suggest the presence of cancer. The DRE is also used to estimate the volume of the prostate and can sometimes help determine the extent of the cancer.
Unlike the standard approach taken by most urologists, where the patient is asked to bend over a table for the digital exam, we perform digital examinations of the prostate with the patient in the dorsal lithotomy position – lying on his back with his legs drawn up (much like the position a woman is in for a pap smear – see illustration). This position causes the prostate gland to literally fall naturally against the physician’s fingers, allowing for a more complete and relaxed examination of the gland.
To perform the rectal exam, the doctor feels the gland by placing a lubricated, gloved finger inside the rectum against the prostate. When done properly, the test is not as discomforting as it might sound. Most cancers are located in the back of the prostate, and some of these cancers that have grown at the edge of the gland can be felt as a lump or hard nodule. Depending on the size, shape and location of the lump, it is sometimes possible to determine with a DRE if the cancer is likely to have spread beyond the prostate capsule. With the DRE, the doctor is able to evaluate the major portions of the gland’s anatomy: the right and left sides or lobes; the upper portion of the base of the gland the middle portions of the gland’s anatomy; the right and left sides or lobes; the middle portion of the gland; and lower portion or apex. However, not all surfaces of the gland can be reached by the DRE.
Unfortunately, the DRE is often not accurate. Many prostate cancers do not protrude against the back of the gland; they are not palpable and cannot be detected with the DRE. A tumor at the front of the prostate cannot be felt through the rectum. In addition, the test is subjective and depends on the skill of the doctor, providing at best only an estimate of the extent of the disease. Many surgical studies have shown that more than 50% of cancers that appear to be confined to the gland will later be found to have spread beyond the gland. However, DRE is important as it is sometimes able to reveal tumors that would have been missed by PSA blood test alone.
The PSA test was developed during the late 1970’s by research scientists at Roswell Park Memorial Hospital in Buffalo, New York. The PSA is a blood test that measures the amount of prostate specific antigen (PSA) present in the body. Produced almost exclusively by the prostate gland, PSA is an enzyme, typically present in only minute quantities, secreted into the bloodstream from blood vessels inside the prostate.
PSA secretions originate from cells in the lining of the prostate gland. When prostate cancer is present, additional PSA is usually produced. This extra PSA can be detected and measured in the blood through a simple laboratory test, which can be ordered by any primary-care physician. Test results are usually available in several days, or possibly longer depending on the assay used.
Because cancerous cells readily leak PSA into the surrounding body tissue, an elevated PSA is a possible indicator of the presence of prostate cancer. However, other conditions can also cause an elevated PSA. The most common is the enlargement of the prostate gland that occurs with BPH (benign prostate hypertropy). Infections and traumas such as a biopsy or even an overly vigorous digital rectal exam can sometimes increase PSA levels. Ejaculation (orgasm) can elevate PSA for as long as 48 hours.
As a diagnostic tool, the PSA test has its limitations, and is usually combined with the DRE and other tests. Some men with seemingly normal PSA values turn out to have prostate cancer that may be detected with the DRE or another diagnostic test. A more aggressive cancer may sometimes be associated with a palpable tumor (a least a billion cells) found by DRE and normal or even low PSA.
Standard PSA test results are reported in nanograms per milliliter (ng/ml), with a normal range of approximately 0-4 ng/ml. For the sake of simplicity, the units of measure will not be included in the remainder of this discussion. The normal range of PSA values must be adjusted slightly to account for differences in age and race. As men get older, the normal PSA range slowly increases. This normal range is generally lower for Caucasion males than for Asians and Afro-Americans.
Regardless of age and race factors, PSA levels greater than 10 are most often an accurate indicator of cancer. As many as 80 percent of men with this an elevated PSA reading (and positive digital rectal exam) have been shown to have prostate cancer. Approximately 25 percent of those patients with a PSA between 4 and 10 turn out to have cancer, as confirmed by standard prostate biopsies. The accuracy of the PSA test is significantly improved when it is combined with the digital rectal exam. The PSA can detect twice as many cancers as the DRE alone; however, the DRE spots some cancers that may be missed by the PSA.
It should be stressed that the PSA test is not conclusive by itself in diagnosing prostate cancer. No treatment decision should ever be made on the basis of the PSA value by itself; however, an elevated PSA reading may suggest the need for further laboratory tests. A biopsy of the prostate gland is always necessary to confirm the presence of cancer.
Because the PSA test is not completely reliable as far as its predictive value, a patient with a high PSA level may not necessarily have cancer and a patient with a very low PSA may not be cancer free. In fact, high grade, more aggressive cancers can lose their resemblance to prostate cells altogether and may not even produce PSA. The PSA provides only a statistical approximation, and there are often exceptions. PSA results are discussed in terms of probabilities, the likelihood of prostate cancer being present, and the likelihood that it may have spread beyond the prostate gland.
What do I do if I have a rising PSA with a negative Biopsy(-s)
Unfortunately, some men find themselves in the frustrating and frightening position of having a continuing increasing PSA with negative biopsy results. Some of these men believe they have cancer and that the biopsy needle has simply missed it. Others are uncertain what to think. Most are confused how to proceed or what to do next. If your doctor is attempting to distinguish between prostate cancer and BPH, there are several additional factors relating to PSA that can be considered:
PSA velocity refers to the rate of change of the PSA over time. The measurement of PSA velocity is known as PSAV or PSA slope. The assumption is that the annual rate of change of the PSA value for men with cancer is greater than for men without cancer, both those with normal prostate glands and those with BPH. A rise in the PSA of 0.75 or more in a year may be an indicator of cancer. A rise in the PSA less than 0.75 might indicate BPH, or could be a fluctuation attributed to a normal prostate.
Studies have shown that the use of PSA velocity can reduce the number of unnecessary biopsies. For patients with BPH, the number of biopsies may be reduced from 40 percent to 10 percent. PSA velocity can be especially telling for patients whose PSA is within the normal range but not increasing rapidly. For example, a patient whose PSA rises from 1.3 to 2.3 to 3.7 over a period of two years might have a cancer detectable with a biopsy even before his PSA climbs about the” normal limit” of 4.0. This is where the benefit of early detection becomes most obvious, as the cancer can be caught when it is most treatable.
PSA velocity is also useful in diagnosing those patients whose PSA values are in the gray area between 4 and 10, and who have negative biopsies. For example, a patient with a 5.8 PSA value and negative biopsy might undergo another biopsy the following year if his PSA climbs significantly. An increase in PSA of less than 0.75 may rule out the need for another biopsy. The measurement of the PSA values over time greatly increases the ability of a doctor to make an accurate clinical diagnosis. For the best results, the patient is usually advised to have his PSA tested at least three times over a period of two years.
While the PSA test can be very important, and may be the single most important marker to determine the likelihood of cancer being present, the PSA alone may not be as important as the PSA velocity. The history of the patient’s PSA over time also enables us to calculate the doubling time (PSADT) – the amount of time it takes for the PSA value to double – which can help us determine how rapidly the cancer is growing. A PSADT of less than 2 years and a PSA velocity greater than 0.75 indicate greater likelihood of malignancy.
Several other approaches for measuring PSA levels can allow us to make a more accurate diagnosis. Among these are free (or unbound) versus bound (or complexed) PSA. These terms refer to the fact that PSA appears in the bloodstream in two distinct molecular forms, either unattached to the other substances (free), or combined with other protein molecules (bound). The percent-free PSA test measures how much PSA circulates free in the bloodstream compared to the total PSA level. The percentage of free PSA tends to be lower in men who have prostate cancer than men who do not.
Some studies indicate that the amount of bound PSA in the blood is higher when cancer is present, while the amount of free PSA is higher in men with BPH. The percentage-free PSA test is especially useful for diagnosing patients whose PSA falls into the gray area between 4 and 10, and even at lower levels between 2.5 and 4 – when it is most difficult to distinguish cancer from benign enlargement of the prostate (BPH). By increasing the accuracy of PSA testing in this way, the number of unnecessary biopsies can be reduced.
A careful analysis of these considerations will help you have a better understanding of the likelihood that you may or may not have cancer. However as previously discussed, the only way to know for certain is by removing tissue from the prostate (i.e., biopsy) and examining it under a microscope to determine if cancerous cells are present. If you’ve already had one or several negative biopsies, and you believe that your blood work indicates cancer, you may want to consider a more active and assertive role in your care by seeking out a physician able to perform a biopsy using the aid of color-flow Doppler Ultrasound. This equipment was called “the best kept secret in Urology” during a recent international conference on prostate cancer due to its ability to help physicians see suspicious areas that may be cancerous. With this new information the biopsy needle can be directed to those suspicious areas, to give doctors the best chance to answer to the question of whether or not you have cancer.
