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Diagnosing prostate cancer
Diagnosis is the process of finding the underlying cause of a health problem. If cancer is suspected, the healthcare team will confirm if it is present or not, and what type of cancer it is. The process of diagnosis may seem long and frustrating, but it is important for the doctor to rule out other possible reasons for a health problem before making a cancer diagnosis.
Diagnostic tests for prostate cancer are usually done when:
- the symptoms of prostate cancer are present
- the doctor suspects prostate cancer after talking with a man about his health and completing a physical examination
- tests suggest a problem with the prostate
Many of the same tests used to initially diagnose cancer are also used to determine the stage (how far the cancer has progressed). Your doctor may also order other tests to check your general health and to help plan your treatment. Tests may include the following.
The medical history is a record of present symptoms, risk factors and all the medical events and problems a person has had in the past. The medical history of a man's family may also help the doctor to diagnose prostate cancer.
In taking a medical history, the doctor will ask questions about:
- a family history of prostate cancer or other cancers
- signs and symptoms, such as any changes in bladder habits
A physical examination allows the doctor to look for any signs of prostate cancer. During a physical examination, the doctor will do a digital rectal examination (DRE):
- DRE allows the doctor to check the prostate. During a DRE, the doctor places a gloved finger into the rectum to feel the prostate gland through the wall of the rectum.
- A normal prostate feels smooth and rubbery. The doctor will check the prostate for any lumps or changes in size, shape or consistency of the prostate.
- DRE may find cancer in the peripheral zone, the part of the prostate closest to the rectum, which is where most prostate cancers develop.
The doctor may also:
- feel the bladder through the abdomen to see if it is enlarged or distended
- check the kidneys for lumps or tenderness
- check for tender or painful bones
A prostate-specific antigen (PSA) test is done to measure the level of PSA in the blood. PSA is a tumour marker. PSA is a protein made by the prostate. When it is present in the blood in abnormal amounts, it may indicate the presence of prostate cancer.
- The PSA level can be increased in men with prostate cancer, but it can also be increased in men with non-cancerous conditions such as an enlarged prostate (benign prostatic hyperplasia, or BPH) or infection or inflammation of the prostate (prostatitis).
- The PSA level varies with age and tends to rise gradually in older men.
- Changes in the PSA level over time can indicate the chance of having cancer.
- A slow increase over several years is usually due to aging.
- An increase by 1 each year is more worrisome for cancer.
- The higher the PSA level, the more likely that prostate cancer is present.
- Because PSA is a tumour marker, the PSA test is also used to check a man's response to prostate cancer treatment.
Ultrasound uses high-frequency sound waves to make images of structures in the body. A transrectal ultrasound (TRUS) uses an ultrasound probe placed into the rectum to make images of the prostate. It is used to:
- measure the size of prostate
- look for abnormal or suspicious areas
- direct the placement of biopsy needles so that samples of tissue may be taken from the prostate
A biopsy is used to diagnose prostate cancer. A prostate biopsy may be done if an abnormality was found during a DRE or transrectal ultrasound. It may also be done if the PSA level was high for a man’s age or has increased over time or rapidly.
During a biopsy, tissues or cells are removed from the body so they can be tested in a laboratory. Several (6–12) biopsies are usually taken from the prostate. They are collected from several areas of the whole prostate as well as from any suspicious areas. The pathology report from the laboratory will confirm whether or not cancer cells are present in the sample. If prostate cancer is present, the samples are used to determine the Gleason score. The Gleason score describes how aggressive the prostate tumour is and how likely it is to spread.
Biopsies of the prostate are usually done using transrectal ultrasound (TRUS), which helps the doctor guide the biopsy needle to the prostate gland. Doctors can collect cells or tissues from the prostate through different approaches.
During a transrectal biopsy, the doctor uses TRUS to insert a thin needle through the rectum and into the prostate. Samples of cells or tissue are removed from the prostate through the needle.
Sometimes the doctor will use TRUS to do a prostate biopsy through the skin of the perineum. The perineum is the area between the scrotum and the rectum. The doctor inserts a needle into the perineum and cells or tissue are removed from the prostate.
The urethra is the tube that carries urine from the bladder and out of the body through the penis. During a transurethral biopsy, the doctor inserts a cystoscope (a long, thin tube with a light and lens) into the urethra. Cells or tissue can be collected from the prostate through tools passed through the cystoscope. However, transurethral biopsy is not usually used to diagnose prostate cancer.
A complete blood count (CBC) measures the number and quality of white blood cells, red blood cells and platelets. A CBC is not used for staging, but may be done to:
- provide information about a man's general health
- check for infection
Blood chemistry tests measure certain chemicals in the blood. They show how well certain organs are functioning and can also be used to detect abnormalities. They are used to help stage prostate cancer.
- Blood urea nitrogen (BUN) and serum creatinine are measured to check kidney function. If these are higher than normal, it may mean that the prostate is blocking the ureters, the tubes that carry urine from the kidneys to the bladder.
- Increased alkaline phosphatase may indicate that prostate cancer has spread to the bone.
- Increased calcium may indicate that prostate cancer has spread to the bone.
A bone scan uses bone-seeking radioactive materials (radiopharmaceuticals) and a computer to create a picture of the bones. It is used to see if the prostate cancer has spread to the bones (the most common place where prostate cancer spreads). It may be done if:
- test results suggest spread to the bone, such as increased alkaline phosphatase or calcium level
- a man has unexplained bone pain
A bone scan is not usually done when the chance of cancer spread to the bone is very low, such as in men with:
- a low Gleason score (7 or less)
- a PSA level of 20 or less
A CT scan uses special x-ray equipment to make 3-dimensional and cross-sectional images of organs, tissues, bones and blood vessels inside the body. A computer turns the images into detailed pictures. It is used to determine if the cancer has spread to the lymph nodes around the prostate gland. A CT scan is usually useful only for men diagnosed with prostate cancer who have a high PSA level (over 40) and a high Gleason score (over 7).
MRI uses powerful magnetic forces and radio-frequency waves to make cross-sectional images of organs, tissues, bones and blood vessels. A computer turns the images into 3-dimensional pictures. An MRI can sometimes show details that are not visible on a CT scan. An MRI may be used to see if prostate cancer has spread to the lymph nodes near the prostate or to surrounding tissues or structures.
A pelvic lymph node dissection may be done to examine lymph nodes in the pelvis to see if the prostate cancer has spread. It may be done at the same time as surgery to remove the prostate (radical prostatectomy) or it may be done as a separate procedure in men who have a PSA level greater than 20 and a high Gleason score (8 or higher). The procedure may be done through an incision in the abdomen or using a laparoscopelaparoscopeA procedure that uses an endoscope (a thin, tube-like instrument with a light and lens) to examine or treat organs inside the abdomen and pelvis..
A pelvic lymph node dissection is not commonly done at the same time as removal of the prostate in men with a low risk of prostate cancer spreading to the pelvic lymph nodes. This is because the chance of cancer spread is usually very low and the lymph node dissection has side effects.