Diagnosis and Prognosis of Prostate Cancer
Because early prostate cancer rarely displays any noticeable symptoms, the diagnosis of prostate cancer usually begins in your doctor’s office during a routine physical examination. The diagnosis and prognosis process includes the following:
During a routine exam, your doctor will usually ask about your medical history, including information about possible risk factors related to prostate cancer. A thorough physical exam includes a digital rectal exam and blood tests, including a measure of the blood level of prostate specific antigen (PSA).
Digital rectal exam – your doctor inserts a gloved, lubricated finger into the rectum, in order to examine the prostate gland. Your doctor can then determine if the prostate gland feels normal or enlarged, and if the texture is normal and smooth, or hard and irregular (as a cancerous prostate gland would sometimes feel).
Prostate Specific Antigen (PSA) test – PSA is a chemical that indicates abnormalities in the prostate—an elevated PSA can mean there is a problem in the prostate. PSA levels can sometimes increase directly following manipulation of the prostate gland (as occurs during a digital rectal exam), therefore, blood for a PSA test should be drawn before your physical exam, or on a different day.
The PSA level increases with age, even in men without cancer. It can be elevated for a number of reasons other than cancer, including infection of the prostate or benign prostatic hypertrophy (BPH), a condition in which the prostate is enlarged but not cancerous.
If rectal exam of your prostate seems abnormal or your PSA test is elevated, your doctor will need to perform further testing to determine if you have prostate cancer, benign prostatic hyperplasia, an infection, or some other condition.
Anatomy of the Prostate Gland
Further testing to help make a diagnosis may include the following:
PAP blood test – another blood test often done is the prostatic acid phosphatase (PAP). PAP is an enzyme found in men's urine and semen. When there is an abnormality in the prostate, PAP is released into the blood stream and will be elevated on a blood test. This test is not as good a measure for the diagnosis of prostate cancer as the PSA.
Urine tests – a urine sample is tested for the presence of blood or infection.
Transrectal ultrasonography, or ultrasound – an ultrasound probe is placed into the rectum as close to the prostate as possible. The probe releases painless sound waves that bounce off the inner tissues of the prostate. The echoes produced by the sound waves create a picture on a computer screen that helps distinguish normal prostate tissue from cancerous tissue.
Biopsy – if, based on the tests above, your doctor is concerned about the possibility of prostate cancer, a biopsy may be recommended. The doctor removes a small amount of tissue from the prostate to be sent to the laboratory for exam. There are several procedures used to obtain a tissue sample, including the following:
- Transrectal biopsy – the biopsy sample is obtained by inserting a needle through the wall of the rectum into the prostate gland. Transrectal ultrasound is used to help the doctor guide placement of the needle into the prostate. The area of the biopsy may be numbed. Several samples are taken from different areas of the prostate gland using an extremely quick biopsy “gun” that removes a tiny core sample of tissue. This procedure takes about 30 minutes and is done in the doctor’s office.
- Transperineal biopsy – the biopsy is obtained through the perineum, which is the area of skin between the scrotum and rectum. A needle is inserted either directly through this skin into the prostate gland, or through a tiny incision made into the perineum. This is done far less frequently than the transrectal biopsy.
Grading and Staging
If cancer is found on biopsy, prognosis and treatment depend on the grade of the cancer cells, the size of the tumor, PSA value, and stage of the cancer, as well as your general health.
Grading is a way of rating the cancer cells. Higher scores mean the cells are more abnormal and aggressive, and therefore more likely to grow quickly and spread.
Grading is done through examination of the cancer under a microscope by a pathologist. The cancer is assigned a number, one through five. The higher the number, the more abnormal the cells, and the more greatly they differ from normal prostate cells. The scores of the two most prevalent growth patterns seen are added together to arrive at the Gleason’s score, which can range from 2-10. A low Gleason’s score means the cells appear more normal, and may therefore be expected to be less aggressive. A higher Gleason’s score means that the cells look very abnormal, and may be more likely to grow quickly and spread.
Staging is the process by which physicians determine the prognosis of a cancer that has already been diagnosed. Staging is essential for making treatment decisions (e.g., surgery vs. chemotherapy). Several features of the cancer are used to arrive at a staging classification, the most common being the size of the original tumor, extent of local invasion, and spread to distant sites (metastasis). Low staging classifications (0 – 1) imply a favorable prognosis, whereas high staging classifications (4 – 5) imply an unfavorable prognosis
Additional tests to determine staging may include the following:
- Urine and blood tests
- Additional physical exam
- X-rays of various parts of the body
- Bone scan – a nuclear medicine scan that uses radioactive material injected into your body to detect abnormal areas of bone which could indicate spread of cancer.
- CT scan or CAT scan – a series of x-rays put together by a computer to make detailed pictures of areas inside the body.
- ProstaScint scan – an injection of a radioactive compound called technetium is given. Three hours later, you lie on a table. Special cameras move slowly above and below the table taking pictures; these cameras detect small amounts of radioactivity in the injected technetium. This allows the doctor to see areas of the bone that may contain cancer cells that have traveled outside of the prostate. This study is still investigational and has not yet proven to change management of your disease.
- MRI scan – a test that uses magnetic waves to produce images of the inside of the body. Using a large magnet, radio waves, and a computer, an MRI produces two-dimensional and three-dimensional pictures.
- Lymph node biopsy (pelvic lymphadenectomy) – all or part of one of your lymph nodes is removed and examined under a microscope. The biopsy can show whether or not there is cancer and what type of cells are present. This is sometimes done before removal of the prostate.
Several staging systems are in use for prostate cancer. Perhaps the most commonly used system is called the TNM system. This system characterizes three aspects of prostate cancer: information about the tumor (T), the lymph nodes (N), and the presence of distant metastasis (M). As with grading, the higher numbers reflect a greater degree of abnormality and spread.
Prostate Tumor (T)
- TX: Tumor cannot be evaluated.
- T0: There is no evidence of tumor.
T1: Tumor may be present, but cannot be felt during digital rectal exam nor visualized during imaging tests:
- T1a: Tumor is present, but was found during surgery for some other condition. The total volume of tumor is only 5% or less of the prostate volume.
- T1b: Tumor is present, but was found during surgery for some other condition. The total volume of tumor is 5% or more of the prostate volume.
- T1c: Presence of cancer cells in prostate was identified during needle biopsy.
T2: Tumor is present only within the prostate:
- T2a: Tumor is present in only half a lobe or less of the entire prostate.
- T2b: Tumor is present in more than half a lobe but not both lobes of the prostate.
- T2c: Tumor is present in both lobes of the prostate.
T3: Cancer cells extend through the tissue that covers the prostate (the capsule):
- T3a: The tumor extends through the capsule of the prostate.
- T3b: Tumor cells are evident within the seminal vesicles (these are paired sacs attached to the base of the prostate)
- T4: Tumor extends into tissues beyond the seminal vesicles into the bladder neck, the external anal sphincter, the rectum, or the walls of the pelvis.
Lymph Nodes (N)
- NX: Nodes cannot be evaluated.
- N0: There are no cancer cells in the regional lymph nodes.
- N1: Metastases in regional lymph nodes.
Distant Metastasis (M)
- MX: Presence of metastasis cannot be evaluated.
- M0: There is no distant metastasis.
M1: There is distant metastasis:
- M1a: Distant lymph nodes are cancerous.
- M1b: Bone is involved.
- M1c: Another site or sites are involved.
Staging Based on the TNM system Is as Follows:
- T1a, NO, MO, low Gleason score (2-4)
- T1a, NO, MO, intermediate or high Gleason score (5-10)
- T1b, NO, MO, any Gleason score (2-10)
- T1c, NO, MO, any Gleason score (2-10)
- T2, NO, MO, any Gleason score (2-10)
- T3, NO, MO, any Gleason score (2-10)
- T4, NO, MO, any Gleason score (2-10)
- Any T, N1, MO, any Gleason score (2-10)
- Any T, any N, M1, any Gleason score (2-10)
Prognosis is a forecast of the probable course and/or outcome of a disease or condition. Prognosis is most often expressed as the percentage of patients who are expected to survive over five or ten years. Cancer prognosis is a notoriously inexact process. This is because the predictions are based on the experience of large groups of patients suffering from cancers at various stages. Using this information to predict the future of an individual patient is always imperfect and often flawed, but it is the only method available. Prognoses provided in this monograph and elsewhere should always be interpreted with this limitation in mind. They may or may not reflect your unique situation.
Prognosis depends on both grading and staging. In general, the higher the grade and the stage, the poorer the prognosis.
American Cancer Society
National Cancer Institute
Last reviewed February 2003 by Donald Lawrence, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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