Family doctor

OVERVIEW

Many men are aware  that there is a blood test (PSA=prostatic specific antigen) that can help look for prostate cancer. It is important that men undergoing the test have an understanding of the likely probable benefits and drawbacks.

 There is ongoing controversy as to how beneficial widespread (population based screening) screening is, with most experts against screening on the grounds that the net benefit (in terms of prolonged life) is very small compared to the psychological and physical harms that may follow on from diagnosis and treatment. Currently there is no good evidence that a population based screening program would reduce mortality (risk of death from prostate cancer).

The aim of any screening test is really to prevent premature death from the condition concerned, in this case Prostate cancer.

It is important to understand that although prostate cancer is common form of cancer, it is predominantly a disease of older men and is very slow growing in most cases.

The following table should help put the risks of getting and dying from prostate cancer in some perspective.

Population risks of prostate cancer diagnosis and death, Australia

1997–2001 (per 1000 men)

Some facts about the PSA test

It is a screening test and will not on its own give an answer as to whether or not you have cancer. Further testing with a prostate biopsy would be required to help ascertain if cancer was present

Firstly, around 20 % of cases where prostate cancer is present may have a normal PSA.

Of those patients with a raised PSA who go on to have a prostate biopsy to look for cancer, around two thirds will not have cancer confirmed.

Even the biopsy is not a fail-safe, with around 20% of prostate cancers being missed on standard biopsy techniques.

Recently (2009) a couple of high quality trials on prostate cancer screening have provided some useful guidance on benefits.

1-The American PLCO trial, showed that being screened did not reduce the risk of dying from prostate cancer although the risk of finding cancer was increased. Interestingly the death rate from non prostate cancer causes was higher in the screened group (it is possible this related to treatment related mortality.)

It is worth noting however that many in the control group were in fact having PSA tests as part of their routine care and this may have “contaminated” the trial findings although the effect would be small.

This trial was over a 10 year period and the reporting will continue out to 13 years

2-The European ERSPC trial showed a small benefit.

A 20% relative reduction in death rate in the screened group was shown. When expressed as an absolute risk reduction of 0.71 in 1000,this does not sound as impressive.

What this meant is that over the 9 year period of the trial, 1410 men underwent regular screening to prevent 1 prostate cancer death.

To achieve this benefit, 47 other men were treated for prostate cancer who did not receive any mortality benefit, but had all the side effects of treatment.

Put in another way, around 98% of those treated for prostate cancer detected at screening will not experience a prolongation of life, by having undergone screening.

Some argue that longer outcome studies may be needed given the very long history of prostate cancer.

Controversies in treatment

Even once prostate cancer is diagnosed, there is no clear consensus on the best treatment ie surgery, radiotherapy, brachytherapy or watchful surveillance for progression.

Substantial harms may arise from treatment including death; incontinence and impotence, not to mention the potential anxiety from screening itself .These have to be weighed against small potential benefits.

Once informed

Many patients may still decide to have a PSA test  to assess their possible prostate cancer risk- if you decide to proceed, there are a few factors  to consider which may raise the PSA, including

Prostatitis (inflamed prostate)  

Urine infection

Ejaculation (abstain at least 48 hour s pre test)

Physical exercise e.g. cycling

Although traditionally screening has been suggested at the ages of 50-69, some urologists recommend a baseline level at 40 to help stratify future risk and determine the frequency of further monitoring.

The concept of the rate of change in PSA (PSA velocity) can give useful information as to the probability of a more aggressive cancer and the need for biopsy; it is recommended to use at least 3 PSA measurements over an 18 month period.

Other concepts that may add information include

“Free PSA” (less with cancer)   and PSA density (elevated PSA in a small gland more concerning than in a large gland-(determined by ultrasound)

Really useful resources and websites to help your decisions

1-U.S preventive Services task force statement on prostate screening

2-Review of ERSPC and PLCO trials about prostate cancer screening.