Diagnosing Prostate Cancer

by Oliver Moras

Typical tests for prostate cancer at a GP practice are: Taking a urine sample to test for infection, PSA testing and having a digital rectal examination. 

PSA testing is when a blood sample is taken to test for the level of prostate-specific antigens a person has in their blood. Unfortunately, PSA tests are unreliable, suggesting both false-positive results and false-negative results occasionally. 15% of men with prostate cancer still have normal PSA levels so by relying on PSA testing solely, many cases would be missed. On the other hand, the test detects both aggressive prostate cancer that needs treatment and also non aggressive cancer, where symptoms may never be caused and which may never shorten life. This test is unable to differentiate between the nature of the cancer, furthermore, 3 in 4 men with a raised PSA level do not have prostate cancer at all. This may result in both overdiagnosis and overtreatment, where a major issue is that side effects of the treatment could have more serious effects on the body than the cancer would. PSA itself is a protein made by the prostate gland and since some leaks into the blood, blood can be sampled to monitor PSA levels. The degree of leakage depends on age and the prostate’s condition. PSA in the blood is measured in nanograms of PSA per millilitre of blood (3 ng/ml is the base level for a raised PSA level for those aged between 50 and 69). Other than prostate cancer, a raised PSA level could be an indication of an enlarged prostate, prostatitis or an urinary infection. While the test is not reliable and can cause unnecessary worry and medical tests, it can help to diagnose prostate cancer during early stages which results in earlier treatment and a reduced risk of shortened life and death.

People with a raised PSA level may get referred to hospital for an MRI or biopsy. A scan which shows an issue will result in the doctor conducting a biopsy in the target area. The 2 main types of biopsy used are a transperineal biopsy, where under general anaesthetics, a needle is inserted behind the scrotum, or a transrectal biopsy, where a needle is inserted through the rectum. During transrectal biopsies, the patient is normally under a local anaesthetic to reduce discomfort and an ultrasound probe allows the doctor to see where to take the sample tissue from. The main disadvantage of transrectal biopsies is that it has a higher risk of infection. While biopsies are more reliable than PSA testing, the tumor may not be spotted and so the cancer wouldn’t be detected. If the cancer is advanced and there is a chance it has spread, MRI, CT or PET scans may be used to determine if the cancer has spread to the bones.

https://www.nhs.uk/conditions/prostate-cancer/diagnosis/

https://www.nhs.uk/conditions/prostate-cancer/psa-testing/

https://www.nhs.uk/conditions/prostate-cancer/should-i-have-psa-test/