Detecting Prostate Cancer

Many prostate cancers are found by digital rectal examination (DRE) and/or prostate-specific antigen (PSA) testing.

Prostate-Specific Antigen (PSA) Blood Test

Prostate-specific antigen (PSA) is a substance made by the normal prostate gland. Most of the PSA is in semen and normally only a small amount escapes into the blood. Most men have levels under 4 nanograms per milliliter (ng/ml) of blood. But when prostate cancer develops, the PSA level usually goes above 4. Still, about 15% of men with a PSA below 4 will have prostate cancer when a biopsy is done. A man with a PSA level in the borderline range between 4 and 10 has about a 1 in 4 chance of having prostate cancer. If the PSA level is more than 10, the chance of having prostate cancer is over 50% and increases more as the PSA level increases. PSA levels estimate how likely a man is to have prostate cancer, but the test does not provide a definite answer. The diagnosis of prostate cancer can only be made by removing a sample of prostate tissue for examination (biopsy).

PSA is used as an early detection test for prostate cancer. It is also used to follow the status of the cancer in someone who has been treated. PSA is also made by the small intestine, breast, and salivary and parotid glands, so sensitive tests may detect PSA levels in very low levels (0.01–0.05). However, after surgery to remove the entire prostate the PSA level should drop to near 0 and levels should remain very low or even undetectable. If it doesn’t completely fall to near 0, cancer may still be there. Or if it does drop to near 0 and then rises, it is likely the cancer has come back. After radiation therapy, the cancer usually falls to a low level but not 0. Once again if it begins to rise from this low point, then it is likely the cancer is growing back.

The PSA test can also help predict prognosis (outlook for survival). Men with very high PSA levels are more likely to have cancer that has spread beyond the prostate and are less likely to be cured or have long survival.

PSA levels can be used with clinical examination results and the tumor’s Gleason score (see below) to help determine which tests are needed for further evaluation and decide which is the best treatment option.

Digital Rectal Exam (DRE)

During this examination, also known as DRE, a doctor inserts a gloved, lubricated finger into the man’s rectum to feel the prostate for any irregular or abnormally firm area that might be a cancer. The prostate gland is located directly in front of the rectum. Most prostate cancers begin in the part of the gland that is nearest the rectum and can be reached by a rectal exam.

This exam is also used once a man is known to have prostate cancer in order to help predict whether the cancer has spread beyond his prostate gland.

Diagnosis of Prostate Cancer 

History and Physical Exam

When your doctor “takes a history,” he or she will ask you a series of questions about your symptoms and risk factors. Most early prostate cancers cause no symptoms and are found by early detection testing. Advanced 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 enlargement (BPE). Other symptoms of advanced prostate cancer may include blood in the urine, swollen lymph nodes in the groin area, impotence (difficulty having an erection), and pain in the pelvis, spine, hips, or ribs. These symptoms may also be caused by other diseases and do not always mean that a man has prostate cancer. A physical exam to look for prostate cancer will include a DRE of the prostate. A general physical exam is also important in helping to detect or evaluate any other medical problems.

Transrectal Ultrasound (TRUS) and Biopsy

Transrectal ultrasound (TRUS) uses sound waves to create a picture of the prostate on a video screen. Sound waves are released from a small probe placed in the rectum. The same probe detects the echoes that bounce back from the prostate tissue, and a computer translates the pattern of echoes into a picture.

If the doctor suspects prostate cancer because of the results of early detection tests or because of certain symptoms (such as blood in the urine, difficult urination, or pelvic pain), a biopsy of prostate tissue will be recommended to determine if the disease is present. A biopsy is the only way prostate cancer can be diagnosed.

A core needle biopsy is the main method used to diagnose prostate cancer. The doctor will use TRUS for guidance and place a narrow needle through the wall of the rectum into the prostate gland. The needle removes a cylinder of tissue, usually about one-half inch long and one-sixteenth inch across. This tissue is sent to the lab and examined under a microscope to see if cancer is present. The procedure is usually done in the doctor’s office or outpatient clinic and takes less than half an hour. Though the procedure sounds painful, it typically causes little discomfort because a special instrument, called a biopsy gun, inserts and removes the needle in a fraction of a second. The doctor also may numb the area with a local anesthetic.

If the TRUS doesn’t show a tumor, biopsy samples are taken from many different areas of the prostate. Usually 6 to 12 cores are removed (from upper, mid, and lower areas of the left and right sides) to get a good sample of the gland and tell how much of the gland (if any) is affected by the cancer.

If the doctor looking at the biopsy under the microscope (a pathologist) believes it looks suspicious, meaning that some cells do not look normal but are not clearly cancerous, the biopsy may be repeated and may include more samples of the prostate.

Cancer Grade or Gleason Score

If a cancer is found, it will be graded to estimate how aggressive it is likely to be. The tissue samples taken during the prostate biopsy are examined and graded according to how closely they look like normal prostate tissue when viewed under a microscope.

The most commonly used prostate cancer grading system is called the Gleason system. This system assigns 2 grades, a primary and secondary grade. Each grade ranges from 1 through 5 based on the ability of the cancer cells to form glands. If the cells are arranged in clusters that look like the glands of normal prostate tissue, a Gleason grade of 1 is assigned. If the cancer lacks these features and its cells seem to spread unevenly through the prostate, it is a grade 5 tumor. Grades 2 through 4 have intermediate features. Because prostate cancers often have areas with different grades, 2 grades are given. There is a primary (most common pattern) grade and a secondary (second most common pattern) grade. These grades are assigned to the 2 areas that make up most of the cancer. The Gleason primary and secondary grades are added (e.g., 3 + 2 = 5) to yield the Gleason score (range 2–10). The higher the score, the more likely it is that the cancer will grow and spread quickly.

Lymph Node Biopsy

The purpose of this test is to find out if cancer has spread from the prostate to nearby lymph nodes. This is only done before surgery or radiation therapy if a computed tomography (CT) scan or magnetic resonance imaging (MRI) (see below) shows enlarged lymph nodes.

If lymph nodes look enlarged on the imaging study, a specially trained radiologist may take a sample of cells from a lymph node by using a technique called fine needle aspiration (FNA). In this procedure, the doctor uses a CT scan image to guide a long, thin needle into the lymph node. A syringe attached to the needle is used to take a small tissue sample. If cancer cells are found in the lymph node biopsy specimen, surgery is usually not attempted. Instead, other treatment options are considered because the cancer has probably spread to other areas too. There are several other ways lymph node biopsies are done.

During prostate surgery, the surgeon may remove lymph nodes through an incision in the lower part of the abdomen (belly). This is often done in the same operation as the planned radical prostatectomy (discussed later). If the lymph nodes contain cancer, the prostate may not be removed and further treatment may be given.

In some cases, the surgeon may use a laparoscope, which is a long, thin, flexible tube inserted into the abdomen through a very small incision. Using one or more other small incisions, the surgeon can remove the lymph nodes around the prostate gland with special surgical instruments and send them to the pathologist. This procedure (laparoscopic lymphadenectomy) is rarely used.

Blood Tests

A complete blood count (CBC) determines whether the patient’s blood has the correct number of various types of blood cells. Abnormal test results may suggest spread of cancer to the bone marrow, where blood cells are made. Doctors repeat this test regularly in patients treated with chemotherapy because these drugs temporarily affect the blood-forming cells of the bone marrow.

If prostate cancer spreads to the bones it may cause certain chemical abnormalities in the blood. To detect these changes, doctors look at blood chemistry tests for certain substances, such as alkaline phosphatase. Levels of this enzyme often go up in men whose prostate cancer has spread to the bones or liver.

Some of the drugs used in hormone therapy can interfere with liver function. If the cancer spreads to the liver, that can affect liver function, too. These changes in liver function can also be detected by blood tests.

Imaging Tests

These tests use x-rays, magnetic fields, or radioactive substances to create pictures of the inside of the body to look at the extent of spread of the cancer. Several types of imaging tests may be used to look for cancer that has spread beyond the prostate gland, but none of the tests is perfect. Imaging tests are done if early tests, such as the DRE and PSA, and the Gleason score from the prostate biopsy indicate that the cancer is likely to have spread.

Radionuclide bone scan
When prostate cancer spreads to distant sites it often goes to the bone. A bone scan is a test that shows whether the cancer has spread from the prostate gland to bones. For this test you will get an injection of a small amount of radioactive material called technetium diphos­phonate. The amount of radioactivity used is very low and causes no long-term effects. The radioactive substance is attracted to diseased bone cells throughout the entire skeleton over the course of a couple of hours. A special camera then detects the radioactivity and creates a picture of your skeleton. Any areas of diseased bone will be seen on the bone scan image as dense, gray to black areas called “hot spots.” These areas may suggest the presence of metastatic cancer, but arthritis, infection, or other bone diseases can cause similar patterns.

A bone scan is not routinely done before prostate cancer treatment unless there are signs of aggressive disease, such as a significantly elevated PSA level, a high Gleason score, or symptoms that could be caused by cancer.

Computed tomography (CT)
Commonly referred to as a CT or CAT scan, this test uses a rotating x-ray beam to produce detailed cross-sectional images of your body. Instead of taking one picture, as does a usual chest x-ray, a CT scanner takes many pictures as it rotates around you. A computer then combines these pictures into an image of a slice of your body. The machine will take pictures of multiple slices of the part of your body that is being studied.

Often after the first set of pictures is taken, you may be asked to drink 1 or 2 pints of a radio contrast agent or “dye,” or you may receive an intravenous injection of a radiocontrast agent or dye. This helps to better outline structures in your body. You will also need to drink enough liquid to have a full bladder. This will keep the bowel away from the area of the prostate gland. A second set of pictures is then taken. Some people feel flushed or get hives or, rarely, more serious allergic reactions like trouble breathing and low blood pressure can occur. Be sure to tell the doctor if you have ever had a reaction to any contrast material used for x-rays.
The CT scan will give exact information about the size, shape, and position of a tumor and may help find enlarged pelvic lymph nodes that might contain cancer. The CT scan can also detect cancer that has spread to other internal organs, such as the liver.

A CT scan is usually not done to evaluate early stage disease before treatment, unless there is a 7% or more chance that lymph nodes are involved. Your doctor can determine this by checking the information about your cancer with tables called the Partin tables.

Magnetic resonance imaging (MRI)
MRI scans take pictures using radio waves and strong magnets instead of x-rays. The energy from the radio waves is absorbed and then released in a pattern formed by the type of tissue and by certain diseases. A computer translates the pattern of radio waves given off by the tissues into very detailed cross-sectional images of parts of the body. A contrast material might be injected, just as with CT scans. To improve the accuracy of the MRI, many doctors will place a probe, called an endorectal coil, inside your rectum. This must stay in place for 30 to 45 minutes and can be uncomfortable.

MRI pictures can show abnormal lymph nodes or changes in internal organs that suggest cancer may have spread. As with the CT scan, an MRI scan is usually not done to evaluate early stage disease before treatment unless there is reason to believe the lymph nodes may have cancer cells in them.

ProstaScint® scan
The ProstaScint® scan uses low-level radioactive material to find cancer that has spread beyond the prostate. The radioactive material for the ProstaScint® scan is attached to a monoclonal antibody, a type of antibody made in the lab to recognize and stick to a particular substance. In this case, the antibody specifically recognizes prostate-specific membrane antigen (PSMA), a substance found only in normal and cancerous prostate cells. After the material is injected, you will be asked to lie on a table while a special camera creates an image of the body. This is usually done about half an hour after the injection and again 3 to 5 days later.

The advantage of this test is that it has the potential to detect prostate cancer that has spread to bone, lymph nodes, and other organs and may distinguish prostate cancer from other cancers and benign disorders. The disadvantage is the lack of specificity, meaning that it often suggests spread when there is none. The ProstaScint® scan is usually not used to stage the cancer before initial treatment. It may prove to be more useful after treatment in cases where it is thought that the cancer has come back (recurred).

INTRODUCTION

STAGES

For more information on these treatment guidelines, or on cancer in general, call the NCCN at 1-888-909-NCCN or the American Cancer Society at 1-800-ACS-2345. Or you can visit these organizations’ web sites at www.cancer.org (ACS) and www.nccn.org (NCCN).

© 2007 by the National Comprehensive Cancer Network (NCCN) and the American Cancer Society (ACS). All rights reserved. The information herein may not be reproduced in any form for commercial purposes or downloaded and stored in any information-retrieval system without the express written permission of the NCCN and the ACS. Single copies of each page may be printed out for personal, noncommercial use only.