Prostate Cancer Screening

Prostate Cancer Screening

Cancer screening means looking for cancer and detecting it earlier before it causes symptoms.

The goal of screening for prostate cancer is to find cancers that may be at high risk for spreading if not treated, and to find them early before they spread.

The two tests used to screen for prostate cancer are:

1. Prostate cancer antigen (PSA)
2. Digital rectal examination (DRE)

 

PSA CONCEPTS:

Concept 1: The normal PSA

Quite often there is a misinterpretation of what is the normal level of PSA. Usually in many lab tests, they usually inappropriately indicate the normal levels of PSA as 0-4 ng/ml. This is wrong and very misleading.

The normal PSA is the median PSA level in that particular age group of a male.

The normal or median PSA levels are:

40-49 years age: PSA 0.7 ng/ml

50-59 years age: PSA 0.9 ng/ml

60-69 years age: PSA 1.0-1.2 ng/ml

70-79 years age: PSA 1.5-5.0 ng/ml

If the PSA is at the median or less for the age group, then the risk for prostate cancer is very low. If a man’s PSA is higher than the median for his age group, his risk of having prostate cancer is higher and the risk that the cancer is aggressive is also higher.

Increasing PSA level increases risk of prostate cancer:

PSA Level (ng/ml)	Risk of prostate cancer (%)
0-0.5 0.6-1.0 1.1-2.0 2.1-3.0 3.1-4.0	0.0 – 6.6 6.0 – 13.0 12.0 – 17.0 17.0 – 23.9 21.0 – 26.9

It is important to understand this concept of what is the meant by the normal and median PSA.

This is because a trial by Lijla et al in 2007, Vickers et al in 2010, and studies reproduced by others showed that the mid-life PSA (PSA taken in the males in their mid-50 year’s age) predicted the risk of prostate cancer at 20-25 years later. PSA at age 60 years (above the median PSA value) predicts prostate cancer mortality by age 85 years.

A baseline PSA level between the median and 2.5 ng/mL is a significant predictor of future prostate cancer in 20 years, and was associated with a 14.6-fold and 7.6-fold increased risk of prostate cancer in men aged 40 to 49 and 50 to 59 years, respectively.

In other words, a single PSA taken in mid-50s age can predict ones’ risk of future prostate cancer.

If the PSA level is normal and at the median level, then the risk of prostate cancer in future is low.

If the PSA level is higher than the median level, then the risk of prostate cancer in future is higher, and these group of men will require regular PSA surveillance and follow up to detect future prostate cancer.

Concept 2: The PSA test is not a dichotomous test

One needs to understand what the PSA is all about.

The PSA is a continuous variable, and is not dichotomous. The value of doing a PSA is based on the fact that there is an increasing risk of prostate cancer with increasing PSA results. (In other words, the test does not indicate a positive or negative test. A higher PSA poses a higher risk of prostate cancer. This is not like a pregnancy test which will indicate a positive or negative test results).

There is no PSA level below which the risk of cancer is zero. There is no level of PSA which can confidently rule out a prostate cancer.

The higher the PSA level in the blood, the higher risk a person has prostate cancer.

Concept 3: The rising PSA and PSA dynamics

Once an initial PSA has been obtained (known as the initial PSA), the change in the PSA over time, known as the PSA velocity, plays a role in clinical decision making. It is felt that the PSA velocity over a year should be less than 0.75 ng/mL.

For example, a man 50 to 59 years of age with a PSA level that is 0.5 ng/mL one year and increases to 2.5 ng/mL the following year, although he may be viewed as having a normal PSA level, but the rate of change in his PSA (PSA velocity) would be worrisome and suggest an underlying prostate cancer.

 

Controversy in Prostate Cancer Screening

Prostate cancer screening itself is a very controversial issue.

Prostate cancer in general is very slow growing, although the aggressive ones are known to spread fast within 3-5 years. When it is localized and confined to the prostate gland, it may not cause serious harm.

Emerging evidence show that early detection may reduce the likelihood of dying from prostate cancer but this must be weighed against the serious risks incurred by early detection and subsequent treatment, particularly the risk of treating many men for screen-detected prostate cancer who would not have experienced ill effects from their disease if it had been left undetected.

Prostate cancer has a long mean sojourn time, so much so that that it would not cause any problems to a man who is more elderly as it will take time for it to spread. For that reason, many men may not benefit from treatment for prostate cancer and may unnecessarily suffer from its side effects, such as long-term problems with urinary and sexual function.

However the same would not apply to a young man diagnosed with early prostate cancer, especially so if he can live for more than 10-15 years.

Currently until today, it is not possible to differentiate prostate cancers at diagnosis that can grow slowly from those that are aggressive.

Prostate cancer screening is currently not a national screening procedure.

However the following should be noted:

• Screening generally means general population screening unless stated otherwise (although selective screening is also considered screening).
• Individual evaluation of a male with PSA and rectal examination of the prostate, after deciding the risk to benefit ratio, and after understanding the pros and cons of early detection, would be justified.

In other words, there is a difference between population or at-risk population screening which is usually done by national screening guidelines and public health authorities, from that of individual evaluation of a person based on their risk categories on the pros and cons of early detection of prostate cancer.

Debate continues regarding the risks and benefits of prostate cancer screening, and medical organizations differ on their recommendations.

Discuss prostate cancer screening with your doctor. Together, you can decide what’s best for you.

Prostate cancer screening

There are often no symptoms during the early stages of prostate cancer, but screening can detect changes that can indicate cancer.

Prostate cancer screening involves a rectal examination of the prostate and a blood test that measures levels of PSA in the blood. PSA is very specific to the prostate, but not necessarily cancer-specific. High levels of PSA suggest that cancer may be present. To confirm this, a prostate biopsy has to be done.