Date：2021-05-21

Screening Methods For Prostate Cancer

As prostate cancer may have no symptoms in its early stages, many individuals may not be aware that they have it. For those who are uncertain and wish to test for whether they are at risk of it, the digital rectal exam (DRE) and prostate specific antigen (PSA) blood test are common methods for prostate cancer screening.

Digital rectal exam (DRE): The doctor puts on lubricated gloves and inserts fingers into the rectum to check for any abnormal lumps behind the prostate. This test may cause slight discomfort, but it is usually not painful and only takes a short time.

Prostate specific antigen (PSA) blood test: Prostate specific antigen (PSA) is a protein produced by the prostate. The PSA level in the blood can be screened by taking a blood test. The higher the level of PSA in the blood, the greater the possibility of prostate cancer.

Prostate cancer screening refers to the examination of people who are not showing symptoms to find those who are likely to be at a higher risk of developing or have already developed the disease. However, this type of screening cannot be used as a direct diagnosis of prostate cancer. If abnormal results are found via DRE or PSA blood tests, further testing such as prostate ultrasounds and prostate tissue samples should be taken for biopsy to help doctors formally diagnose prostate cancer.

What Should Be Considered Before Proceeding With Prostate Screening?

The accuracy of DRE is reliant on the experience of the doctor who carries out the exam, as it requires the doctor’s interpretation of any physical abnormalities. Furthermore, high levels of PSA in blood tests are not always an indicator of prostate cancer as the increase in PSA level can be caused by other medical conditions, such as benign prostatic hyperplasia and prostatitis. The reliability of prostate cancer screening is therefore not high, with a chance of false positive or false negative results.

False positives in prostate cancer screening: According to the Centre for Health Protection, Department of Health, approximately 5 out of every 6 men who have abnormalities found in DRE do not actually have prostate cancer. Similarly, approximately 3 out of every 4 men found with elevated PSA levels do not actually have prostate cancer. False positive results can cause misplaced anxiety and lead to further unneeded testing for prostate cancer, which holds respective risks.

False negatives in prostate cancer screening: Approximately 1 in 2 men with prostate cancer go undiagnosed by the DRE. Similarly, approximately 1 out of every 4 men with prostate cancer has no increase in PSA level and therefore are inaccurately diagnosed during PSA blood tests. False negative results may lead to men who are at risk of prostate cancer believing that they are not, which may delay them from seeking much-needed medical attention.

Men who do not currently have any symptoms of prostate cancer and intend to undergo prostate screening should consult their doctors to understand the benefits and risks of screening before deciding whether to proceed with further testing. There is a certain aspect of unreliability within prostate cancer screening based on DRE (which tests for physical symptoms) and PSA blood tests (which rely on PSA levels which are also correlated with other medical conditions). As such, genetic testing for the genetic aspect of prostate cancer is a potential pre-emptive option to help determine whether further testing can be pursued, which also presents lower risks. This approach, however, is reliant on an individual’s risk factor for prostate cancer to be genetically inherited, which is not always the case, and therefore cannot be used as a replacement for other cancer screenings.

Family And Genetic Risks Of Prostate Cancer

It is important to note that if an individual has one close relative with prostate cancer, the individual’s prostate cancer risk is three times higher than that of those with no familial relations with prostate cancer; if an individual has two close relatives with prostate cancer, the individual’s prostate cancer risk is five times higher than that of those with no familial relations with prostate cancer.

According to the National Comprehensive Cancer Network (NCCN) patient guidelines, it is recommended that individuals with prostate cancer and those meeting any of the following criteria should be tested for hereditary prostate cancer genes:

• High-risk, very high-risk, regional, or metastatic prostate cancer regardless of family history
• Ashkenazi Jewish ancestry
• A family history of high-risk germline mutations such as BRCA1, BRCA2, or Lynch mutation
• A strong family history of prostate cancer and certain other cancers

Beyond this, certain genetic variants not only increase the risk of prostate cancer in men, but also increase the risk of other cancers. As an example, BRCA1/2 also increases the risk of breast cancer or ovarian cancer in women. Individuals should therefore also pay attention to the genetic dispositions and respective health risks of women in the family.

Reference materials:

HKSAR Department of Health. Cancer Expert Working Group on Cancer Prevention and Screening. Prevention and Screening for Prostate Cancer.

National Comprehensive Cancer Network (NCCN). NCCN Guidelines for Patients. Prostate Cancer Early Stage 2020.