If an individual is suspected to have prostate cancer, detailed investigations are required to establish the diagnosis and stage the disease, which in turn helps in selecting an appropriate treatment option.
Following are some commonly used tests in prostate cancer investigations:
- Digital Rectal Exam (DRE): It is a type of physical examination performed to find any abnormality (bumps or hard areas) in the prostate or nearby structures. In this test, a doctor inserts a lubricated, gloved finger into the rectum via the anus to physically examine the prostate and nearby internal structures.
In case of an abnormality, detailed investigations are required to establish the diagnosis of prostate cancer. But it is not very sensitive, and further testing may be required even if it is normal if there is a suspicion of the disease.
- PSA Assay: PSA is a protein produced by the prostate cells. Its level in the blood increases with age. An elevated level of PSA is generally associated with some prostate abnormalities that can be benign or malignant.
The chance of having a prostate cancer increases with the increase in blood PSA level. Certain variants such as free/total PSA ratio, PSA density, and PSA velocity are more accurate in predicting the disease and differentiating it from benign causes. Although this test does not certainly indicate prostate cancer, it helps in several ways:
Along with other factors (age, race, and family history), it may help to indicate whether further investigations are required.
It can help in determining the overall stage of disease and in determining the appropriate treatment option.
It can also be used to assess the efficacy of treatment and disease progression/recurrence.
- Transrectal ultrasound (TRUS): In this technique, a special rectal probe is used, which directs very high-frequency sound waves towards the internal body parts to be examined. The sound waves are reflected off the internal structures depending upon their ability to reflect these waves and collected by a special detector to produce a real-time image of the internal tissues on a computer screen.
This helps the doctor to examine the prostate along with the nearby structures for any abnormality. This test can measure the size of the prostate or the presence of any abnormalities and can guide a biopsy needle to take biopsy samples from the affected areas. This test does not use any ionizing radiation, and thus, considered as safe. However, it may cause blood in urine or semen for some days, if biopsy samples are collected during the procedure.
- Prostate Biopsy: Many, small biopsy samples are generally collected from the affected areas observed during the TRUS procedure. Prostate cancer is a multifocal disease; thus, about 12 or more biopsy samples are usually collected and screened in a laboratory for further investigations. These samples provide very useful information about the cancer cells such as the type of cancer, grade of the disease, etc.
- Imaging Tests: These tests are generally employed after the establishment of the pathological diagnosis. They help to diagnose the extent of locoregional invasion and spread of disease to the distant organs. Alternatively, these tests are employed after treatment to evaluate the treatment efficacy and to detect any signs of disease progression/recurrence.
Computed tomography (CT) scan: In this technique, detailed cross-sectional images of body organs are generated using x-rays, with or without a contrast medium. It can help diagnose the spread of disease to nearby/distant lymph nodes and other organs, and may also be used to guide a biopsy needle into the affected area.
Magnetic resonance imaging (MRI) scan: This technique provides detailed images of tissues inside the body using radio waves, strong magnetic field, and gadolinium contrast. It can diagnose the extent of invasion and spread of disease to nearby/distant body parts.
Positron emission tomography (PET) scan: This technique uses a radioactive substance (fluorodeoxyglucose [FDG], etc) that is given via intravenous injection prior to the procedure. Cancer cells absorb larger amounts of the radioactive substance than normal cells. The areas of higher radioactivity indicate cancerous tissue on the PET scan. Thus, this technique can diagnose unsuspected spread of disease to distant body parts. It is usually combined with CT scan (PET/CT). PSMA PET/CT is a variant of PET/CT that has higher accuracy for prostate cancer patients as compared to conventional PET/CT.
Bone Scan: In this test, a radioactive material is injected into the vein of the patient, which gets accumulated in the areas of bones affected by the disease, which are then detected with the help of radioactivity detectors. In this way, it may help to detect the spread of cancer to bones.
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Watch the video below to understand the INVESTIGATIONS for prostate cancer required to diagnose and stage the disease.
CancerBro, what are the investigations required to confirm the diagnosis of prostate cancer?
Now we move on to the diagnostic workup prostate cancer.
The diagnostic modalities for prostate cancer are a digital rectal examination, serum markers, prostate biopsy, and imaging.
Prostate-specific antigen or PSA is the biomarker for prostate cancer.
PSA may be falsely elevated in conditions other than prostate cancer.
Most commonly seen are urinary tract infection, bladder catheterization, needle biopsy of prostate and transurethral resection of the prostate.
Normal PSAs levels also vary with the age of a person.
It is less than 2.5 in 40 to 49 years, less than 3.5 in 50 to 59 years, less than 4.5 in 60 to 69 years and less than 6.5 in 70 to 79 years of age.
CancerBro, PSA may be elevated due to so many factors, then how do we know the elevation is due to the disease or other factors?
We can never be 100% sure just based on PSA. It guides us for further investigations and confirms the disease by DRE, biopsy, and imaging.
So to understand it better we come to the free to total PSA ratio.
PSA levels of 4 to 10 are overlapping for benign hypertrophy of prostate and prostate cancer, so free to total PSA ratio will help us to differentiate these two conditions.
If the ratio is less than 10%, it goes in the favor of cancer.
If the ratio is less than 10%, it goes in the favor of cancer.
Next important investigation is a prostate biopsy.
The prostate biopsy may be done under ultrasound or MRI guidance, but the baseline scan should be done as a biopsy may distort the architecture and make it difficult to analyze the scan reports.
Prostate biopsy is assigned a grade called as Gleason’s grade.
For diagnosis of prostate cancer, multiple biopsies are taken from the prostate. In each biopsy sample, we do the Gleason’s scoring.
The scoring is done out of 5, the most common or most predominant score of all the biopsy samples is called as the primary score.
Whereas, the highest score of all the biopsy samples is known as the secondary score.
The total score is calculated by adding a primary and secondary score. The minimum score is 3 in each so the minimum total score is 6.
Score as 6 is called low grade, 7 is intermediate grade and score between 8 to 10 is high grade.