Prostate cancer is one of the largest killers among males worldwide. Until recently, prostate cancer diagnosis has relied on a combination of prostate-specific antigen (PSA) level, digital rectal examination (DRE) and prostate tissue biopsy.
Now, a new test called the PCA3 test checks for prostate cancer based on genetic analysis of cells in the urine. The PCA3 gene codes for the prostate cancer antigen 3 which is produced in higher quantities by prostate cancer cells than normal prostate cells. The cancer cells secrete extremely high levels of PCA3 RNA, which can be detected in the urine.
The PCA3 test is currently still in the experimental phase and is undergoing evaluation in clinical trials. It is therefore not yet available on the NHS but is offered in some private hospitals for around £300 to £400.
Standard tests for diagnosing prostate cancer
Currently, prostate cancer is suspected based on DRE and blood PSA levels and the diagnosis is confirmed using a tissue biopsy. PSA is usually present in small amounts in the blood of healthy men but levels gradually increase with age and are significantly raised in cases of prostate cancer. However, the blood PSA level is not a specific test for prostate cancer, as not all men with prostate cancer may have high levels of PSA and men with high levels of PSA do not always have prostate cancer.
The only reliable way to be sure of a prostate cancer diagnosis is by sending a prostate tissue biopsy for laboratory analysis where the cells are examined under the microscope. Biopsy, however, is an invasive surgical procedure that is associated with risks such as infection, bleeding and pain.
Studies have shown that the non-specificity of the initial DRE and blood PSA test for prostate cancer may be overcome to a large extent with the use PCA3 testing. However, the exact levels of PCA3 that are diagnostic of prostate cancer have not yet been determined. The PCA3 test is still in the experimental phase, but several studies are assessing whether the diagnostic value of this test for prostate cancer can be confirmed.
The PCA3 test would still need to be preceded by DRE, as the prostate needs to be massaged in order for PCA3 to be released into the urine that is sampled. However, it is hoped that the test could contribute towards the elimination of unnecessary biopsy procedures.
Reviewed by Sally Robertson, BSc