To make a diagnosis of prostate cancer, physicians will first conduct a prostate-specific antigen (PSA) test and digital rectal exam. If those signal a potential problem, your doctor will recommend additional tests to establish a diagnosis. Standard diagnostic tests for prostate cancer at Roswell Park include:
- Transrectal Ultrasound (TRUS): A probe inserted into the rectum directs high-frequency sound waves at the prostate, and the echo patterns form an image of the gland on a television monitor. The image reveals the size of the prostate and any irregularities, but it cannot definitively identify tumors.
- Prostate Biopsy: Transrectal ultrasound may also be used to obtain a biopsy where the doctor guides a needle to the correct spot in the prostate gland to collect a tissue sample. The doctors will generally take 12 biopsies, depending on your condition.
Classifying Your Cancer
Pathology tests help to determine the cancer stage and grade or Gleason score — classifications that are essential to choosing the most effective cancer treatment and predicting how the disease will progress.
If cancer cells are found during a biopsy, the pathologist, using an approach known as the Gleason system, will grade the two tissue patterns most common in the cancer. The Gleason system evaluates the ability of the cancer cells to form glands resembling those of a normal prostate. The ability of a tumor to mimic normal gland formation is called differentiation. A number ranging from 1 (well-differentiated) to 5 (very poorly differentiated) is assigned to each pattern. The two numbers are then added together to produce a total Gleason score between 2 and 10. The higher the number, the more aggressive the cancer is likely to be.
After prostate cancer has been diagnosed and a Gleason score has been determined, additional tests are performed to find out if cancer cells have spread to other parts of the body.
- Lymph Node Biopsy: The purpose of this test is to find out if cancer has spread from your prostate to nearby lymph nodes. You may have a biopsy done prior to surgery if your lymph nodes appear enlarged on an imaging study. Most biopsies however, are done during surgery.
- CT Scan: A CT (computed tomography) scan, also called a CAT (computed axial tomography) scan, is a diagnostic exam used to detect tumors, determine the stage and location of a cancer, and find out about the effectiveness of cancer treatment. The CT scan may also be used to guide a doctor who is performing a biopsy. The CT scan obtains multiple cross-sectional images of your body by using special x-rays and computer enhancement, creating an image many times more sensitive than the image from a simple x-ray.
- MRI: MRI (magnetic resonance imaging) is an imaging machine that uses a large magnet, a computer and radio waves to look inside and evaluate parts of the body. This test helps determine if cancer has spread beyond the prostate.
- Radionuclide Bone Scan: This test is often done as part of a checkup to be sure that the bones are free of cancer and also to determine the effects of cancer treatment on the bones. A medication that contains a small amount of radioactive material is injected into a vein in the arm. Radiation rays from the medication make an image on photographic film.