Just diagnosing prostate cancer is not enough. The type of the tumor, the grade, and the stage of the prostate tumor have to be identified so that the proper course of treatment can be decided. Prostate cancer diagnosis, therefore involves a series of procedures to come up with results to help in the treatment.
How abnormal the cancer cells look under the microscope identifies the grade. The stage tells us the size of cancer and whether it has spread.
The candidate is first screened with a digital rectal examination (DRE) and Blood PSA test. These are the first two steps towards the diagnosis of prostate cancer.
If there are sufficient grounds to suspect cancer of the prostate, then further investigations are done.
- Transrectal ultrasound (TRUS)
- Magnetic resonance imaging (MRI)
- MRI-TRUS fusion biopsy
Screening guidelines for prostate cancer diagnosis
Screening means looking for any problems of the prostate gland even when the man has no symptoms. It is recommended in men only after the age of 40 years.
Two tests form the basic screening criteria for prostate cancer. Those are the prostate-specific antigen (PSA) blood test and digital rectal examination (DRE).
They may not be foolproof but any abnormality suggests a ground to investigate the case further.
Your doctor will decide whether you are a candidate for screening. He will ask you if you show any symptoms and have any risk factors. Screening tests can show whether you have signs of prostate cancer that require more testing.
The Urology Care Foundation recommends following certain guidelines to identify a candidate for prostate cancer screening.
1. Analysing symptoms:
Any of the following symptoms could indicate the presence of prostate cancer.
- Incomplete emptying of the bladder
- Increased frequency of urination
- Intermittent urination: stop and start of urination several times when passing urine.
- The urgency to pass urine
- A weak urinary stream
- Straining to start urination
- Nocturia: Increased frequency of urination at night
- How badly are the symptoms affecting the quality of life?
2. Age, family history, and race
- Family history of prostate cancer
- Age between 40 and 69 years
- African American with age between 40 and 69 years
- Age between 55 and 69 years with none of the above
3. Prostate-specific antigen (PSA)
PSA is a protein made only by the prostate. Very little PSA is found in the blood of men with a healthy prostate.
A rapid rise in PSA levels can indicate the presence of prostate cancer. However, benign prostatic hyperplasia (BPH) and prostatitis can also increase PSA levels. Therefore, elevated PSA levels tell us that prostate cancer may be present.
- Most men without prostate cancer have PSA levels under 4 ng/mL of blood. However, a level below 4 does not guarantee that the man does not have cancer.
- Men with a PSA level between 4 and 10 (often called the “borderline range”) have about a 25% chance of having prostate cancer.
- If the PSA is more than 10, the chance of having prostate cancer is more than 50%.
4. Digital rectal examination (DRE)
To perform DRE, the urologist puts a lubricated gloved finger into the rectum and feels the prostate. Because the prostate lies in front of the rectum, this is the way the surgeon can best palpate the prostate.
With a DRE, if the urologist feels hard nodules, generalized firmness, or an unusual increased shape of the prostate, he will suspect prostate cancer and will proceed with further tests to confirm his findings.
Further tests are advised only if any abnormality is found on screening.
Diagnostic procedures for prostate cancer
If prostate cancer screening detects any abnormality, your doctor may recommend further diagnostic tests to determine whether you have prostate cancer. They include:
1. Transrectal ultrasound (TRUS)
The urologist inserts a small cigar-sized probe into the rectum to create a video or take sonographic images of the prostate. This procedure takes about 10 to 15 minutes. A transrectal biopsy of the prostate, if indicated is also done at the same time for the convenience of the patient.
TRUS can detect some tumors that the doctor could not feel by a DRE. It helps the doctor estimate the size of the prostate and the PSA density. This helps the doctor to differentiate between BPH and prostate cancer.
Since it becomes difficult in older men to differentiate between BPH and cancer, doctors use PSA density — the blood PSA level divided by the size of the prostate, as determined by TRUS. This can help distinguish between BPH and prostate cancer.
With BPH, the PSA density does not exceed 15 percent of the prostate size. More than 15 percent can indicate prostate cancer, which should be confirmed by biopsy.
2. PCA3 test for prostate cancer
The prostate cancer antigen 3 gene (PCA3) test is a new test used to determine if you are at risk of prostate cancer. It is not used in the diagnosis of prostate cancer.
The PCA3 test can identify a genetic marker in your urine. If the genetic marker is detected in your urine and your PSA levels are elevated, the elevated PSA levels are more likely to be caused by prostate cancer than by another condition.
This will help your doctor decide whether he should go in for a biopsy or not.
3. Magnetic resonance imaging (MRI)
In some situations, your doctor may recommend an MRI scan of the prostate to get more clarity of the prostate tissue.
An MRI-guided prostate biopsy is the most suitable imaging technique. Researchers noted a 4-times higher cancer detection rate in the MRI-guided biopsy group.
MRI is now being used for staging tumors in combination with other clinical findings.
4. MRI-TRUS fusion biopsy
MRI-TRUS fusion biopsy uses computer software that superimposes images obtained from MRI onto real-time ultrasound for a more accurate targeted biopsy of the prostate.
MRI-TRUS fusion biopsy has shown vast improvement in the detection of clinically diagnosed prostate cancer as compared with the systemic prostate biopsy.
Combining a specialized MRI scan with an ultrasound image helps in precisely targeting the affected area of the prostate that should be biopsied.
5. Prostate biopsy
Prostate biopsy is done transrectally under ultrasound (or MRI) guidance and pieces of the prostate from various suspicious areas are taken for histopathology. Areas are marked from the images taken earlier by TRUS or MRI.
The findings of the MRI and the ultrasound of the prostate are used by the computer software to target the precise prostate area for the biopsy.
The histopath looks for any cancer cells under the microscope and the pathologist then determines the grade (aggressiveness) of the tumor.
After prostate cancer diagnosis how to determine whether prostate cancer is aggressive?
Once the histopathology report confirms the presence of cancer cells in the biopsy sample, the next step is to determine how aggressive the cancer is.
The cancer is graded according to the Gleason Scoring System to determine its aggressiveness.
Cancer cells look different from normal cells when seen under the microscope. The more different they are, the more aggressive they tend to be.
The Gleason system uses the numbers 1 to 5 to grade the primary and secondary appearance of cells found in a tissue sample.
- Grade 1: The tissue appears very much like the normal prostate cells.
- Grades 2-4: Cells that score less, appear very much like normal cells and indicate a less aggressive form of cancer. Those that score higher look much vastly different from the normal cells and indicate fast-growing cancer.
- Grade 5: In the specimens of this grade, most of the cells look very dissimilar from the normal cells.
The Gleason score tells you how aggressive your cancer is and is the sum total of your primary and secondary numbers.
- Gleason score of 6 indicates low-grade cancer.
- A score of 7 indicates a medium aggressive cancer
- A score of 8, 9, and 10 indicates a fast and aggressively growing cancer.
Diagnosing metastasis of prostate cancer
If the presence of cancer is confirmed, your doctor would want to know if it has spread.
More commonly prostate cancer metastasis can occur in the:
- Lymph nodes
Your doctor may prescribe one or more of these imaging tests to detect if your cancer has spread beyond the prostate.
- Bone scan
- Computerized tomography (CT) scan
- Magnetic resonance imaging (MRI)
- Positron emission tomography (PET) scan
While grading of the prostatic tumor tells you how aggressive the malignancy is, staging tells you whether the malignancy has spread outside the prostate.
The results of these tests help the doctor to assign a stage to your cancer. Prostate cancer is staged from I to IV. These stages are set up to tell you how advanced the cancer is.
Stage I indicates that the cancer is confined to the prostate. Stage IV tells you that cancer has spread outside the prostate to other parts of the body.
The American Society of Clinical Oncology (ASCO) has an informative article about the staging and grading of prostate cancer.