If a screening test produces abnormal results, further testing may be recommended in order to diagnose the cause of the problem. Symptoms that also should be taken into consideration when making a diagnosis include any urinary problems or bone pain that a patient might be experiencing.
Common procedures for diagnosing prostate cancer include:
Prostate-specific antigen (PSA) test – If a DRE screening test indicates a problem, a PSA may be given to further test for cancer. A PSA test measures the level of PSA, which is a substance produced by the prostate gland. An elevated level of PSA in the bloodstream can be an indication of prostate infection, inflammation, enlargement or cancer. Additional tests may also be given to form a more thorough diagnosis.
Digital rectal exam (DRE) – If a PSA screening test indicates abnormal findings, a doctor may follow up with a DRE. A DRE is a physical exam of the prostate in which a doctor inserts a lubricated, gloved finger into the rectum and feels the prostate through the rectal wall to check for lumps, irregularities or enlargement. The DRE can sometimes tell whether the cancer is only on one side of the prostate, whether it is present on both sides, or whether it is likely to have spread beyond the prostate gland to nearby tissues. If the PSA or DRE indicate a problem, further testing will be done to help diagnose the cause.
Transrectal Ultrasound (TRUS) – During this procedure, a probe is inserted into the rectum to check the prostate for abnormalities. The probe uses sound waves to form a picture of the internal tissues or organs by bouncing high-energy or ultrasound waves off them. The sound waves enter the prostate and create echoes that are picked up by the probe. A computer turns the pattern of echoes into a black and white image of the prostate called a sonogram.
Transrectal ultrasound also can be used to calculate the size of the prostate, help determine PSA density and more accurately direct needle placement during a biopsy procedure. It is not used as a screening test for prostate cancer because it does not often show early cancer.
Transrectal biopsy – A biopsy is the removal of cells or tissue from the body for examination through a microscope by a doctor called a pathologist. During a transrectal biopsy, a thin needle is inserted through the rectum into the prostate to collect small tissue samples which are then checked by the pathologist who will determine if the tissue sample is cancerous. TRUS is usually used to guide the needles. This is the only conclusive way to diagnose prostate cancer.
Prostate Cancer Grading
Once a biopsy confirms that cancer is present, a doctor will want to determine the grade of the cancer to see how aggressive it is. To determine the grade, tissue samples from the biopsy are studied, and the cancer cells in the sample are compared to healthy prostate cells. The more the cancer cells differ from the healthy cells, the more aggressive the cancer and the more likely it is to spread quickly. More aggressive cancer cells have a higher grade.
The most common scale used to evaluate the grade of prostate cancer cells is called the Gleason system.
This system assigns a Gleason grade, using numbers from 1 to 5 based on how closely the cells in the cancerous tissue look like normal prostate tissue.
- Grade 1 describes cancer that looks very similar to normal prostate tissue.
- Grade 5 is assigned to cancer that lacks normal features and is spread haphazardly through the prostate.
- Grades 2, 3 and 4 have features in between these extremes. Tissue samples can vary in grade as they are taken from different areas of the prostate. For this reason, the pathologist will assign a grade to the two areas in which most of the cancer is found. With few exceptions, these two grades are then added together to yield a Gleason score between 2 and 10.
- Gleason scores of 6 or less are called low-grade or well-differentiated.
- Gleason scores of 7 describe intermediate-grade or moderately-differentiated.
- Gleason scores of 8 to 10 are high grade or poorly-differentiated.
The higher the Gleason score, the more likely the cancer will grow and spread quickly.
Determining if prostate cancer has spread
If a patient’s prostate cancer is believed to have spread beyond the prostate, additional tests may be performed to more completely diagnose the cancer and to determine an appropriate course of treatment. These tests include:
Bone scan – When prostate cancer spreads beyond the prostate, it often invades the bones first. A bone scan can help find cancer that has spread to the bones. During this procedure, a solution is given to the patient by injection or through an IV. This solution travels throughout the body and settles in places where there is abnormal bone tissue. A camera is then used to create pictures of the patient’s skeleton and detect the areas where the solution has settled. These areas may indicate cancer, but can also be other bone diseases, such as arthritis. Additional imaging tests or a biopsy may be used to reach a more conclusive diagnosis.
Ultrasound – Ultrasound is a method of imaging that uses high-frequency sound waves to produce precise images of organs and structures inside the body.
Computerized tomography (CT) scan – A CT scan will help show whether prostate cancer has spread to the lymph nodes or if recurring prostate cancer has spread into the tissue and organs in the pelvic area. During a CT scan, a number of images are taken of a part of the body from many different angles. These pictures are then put together by a computer to create a picture of a cross section of the body. Prior to this procedure, a patient must consume or be injected with a substance called contrast that helps the internal organs stand out more in the images.
Magnetic resonance imaging (MRI) - MRI scans are helpful in determining whether prostate cancer has spread to the bladder or seminal vesicles. During this scan, radio waves and strong magnets are used to produce images of the internal organs and tissues. The energy from the radio waves is absorbed by the body and then released in a pattern formed by body tissue and certain diseases. A computer turns this pattern into a detailed cross-sectional image of the areas of the body that are being scanned, and can show these images from multiple angles.
ProstaScint® scan – The ProstaScint® scan can find prostate cancer cells in lymph nodes and other soft (non-bone) organs. During this test, a solution is injected in the body that settles in places where it finds prostate cells that have spread to other areas of the body. A camera then takes pictures of the body that will produce an image of the internal areas being examined.
This test may be useful after treatment if your blood PSA level begins to rise and other tests are not able to find the exact location of your cancer. Because this test only looks for prostate cells, it cannot detect other types of cancer.
Lymph node biopsy – If a patient’s doctor suspects that prostate cancer has spread to nearby lymph nodes, a lymph node biopsy may be performed. During this procedure, one or more lymph nodes are removed to see if they contain cancer cells. These procedures are referred to as lymph node dissection, lymphadenectomy or lymph node biopsy.
Lymph nodes may be removed by the following methods:
- Surgically through an incision in the abdomen, often done at the same time as a radical prostatectomy (removal of the prostate).
- With a laparoscope (a long, slender tube with a small video camera on the end) which is inserted into the abdomen to let the surgeon see inside the abdomen and allowing for smaller incisions.
- By fine needle aspiration (FNA) in which a CT scan is used to guide a long, thin needle with a syringe attached through the skin into the abdomen where the syringe removes a small tissue sample from a lymph node.