Prostate specific antigen (PSA) in the blood is commonly used to aid in the diagnosis of cancer. Should it be adopted as a routine screening test for the cancer?
THE word “cancer” strikes fear in everyone’s hearts. Among men, prostate cancer ranks as the most common cancer worldwide. In Malaysia, it is the fourth most common cancer diagnosed in men.
For prostate cancer, a test measuring the levels of prostate specific antigen (PSA) in the blood is commonly used to aid in the diagnosis of cancer.
However, the PSA test is increasingly being touted as a routine screening test for men above a certain age. This issue is shadowed by many questions, foremost among them: Should all men take the PSA test? Is it the best method for early cancer detection?
This article will attempt to clear up some of the confusion surrounding PSA testing.
How to know if you have prostate cancer
Most of the time, there are no clear symptoms related to prostate cancer. Some of the symptoms that may develop are not always clear-cut in pointing to prostate cancer as they may also be attributed to other conditions.
For instance, some men with prostate cancer may notice blood in their urine or semen, a need to urinate more frequently, slower than normal urine flow, and difficulty in getting an erection.
These symptoms can also be present in cases of an enlarged prostate, infection and bladder stones. Thus, they are not the most reliable indicators of cancer.
However, if these symptoms are present, your doctor should suspect cancer and conduct several tests to confirm the diagnosis: a digital rectal examination (DRE), a PSA test and/or a prostate biopsy.
A DRE is performed with the doctor inserting a finger into the patient’s anus to feel the prostate. Since the prostate is in front of the rectum, the prostate will be easily felt by pressing the finger on the rectal wall. The surface of the prostate tumour will usually feel irregular and hard.
At the same time, the doctor may also recommend a PSA test. The PSA is a protein produced by cells of the prostate gland. Certain medical conditions, like prostate cancer, prostatitis, urinary tract infection, enlarged prostate, injury and sexual activity, can increase PSA levels.
Because so many conditions can cause the PSA level to go up, it is not safe to presume that it’s prostate cancer from this test alone. Therefore, the doctor may prescribe antibiotics before repeating the PSA test.
It is also advisable to refrain from riding a bike or ejaculating 48 hours before getting a PSA test. If the PSA remains high, a prostate biopsy is recommended.
A prostate biopsy involves inserting an ultrasound probe into the rectum to visualise the prostate. A needle is then used to take samples of prostate tissue via the rectum. The tissues will then be examined by a pathologist through a microscope.
A prostate biopsy will be able to confirm the presence of cancer. However, a negative test does not necessarily rule out cancer because there is a possibility that the biopsy missed the area of the prostate that contained the cancer.
In this situation, a saturation biopsy (where 20-30 biopsy samples are taken) may be needed.
PSA – how high is too high?
There is a lot of controversy over PSA measurements. There is actually no cut-off point for a normal PSA reading, as the level varies with age and race.
The usual upper limit of normal for PSA given by laboratories is 4 ng/ml, across the age ranges.
However, the PSA test is not a diagnostic test; it simply predicts the risk of prostate cancer. It is also worth repeating that any cause of inflammation to the prostate may result in a raised PSA level, so it does not necessarily point to prostate cancer.
There is a high false positive rate for the PSA test – for every 100 cases of raised PSA levels, there may be 76 who do not harbour any cancer!
PSA testing is also used in the treatment of prostate cancer, for active surveillance. Active surveillance is a means of monitoring the prostate cancer, using regular tests, to keep tabs on its progression and delay unnecessary treatment.
In active surveillance, the doctor will monitor the rate at which the PSA level changes (PSA velocity) or the speed at which the PSA values double (PSA doubling time). This allows doctors to determine whether they need to switch to active treatment to treat the cancer.
Do you need the PSA test?
Many men and doctors still believe that the PSA test is a beneficial tool in screening for prostate cancer. However, we need to treat the PSA test with great caution, especially when using it in men who have no signs or symptoms of cancer.
Over 90% of prostate cancers detected by screening are localised or early stage cancers. They are unlikely to cause death or disability because they are slow-growing tumours.
Yet, most of the men with early stage cancers detected through PSA testing will receive treatment for their cancer. This can cause more harm than benefit, as early treatment of prostate cancer identified through screening will lead to side effects, without actually improving survival rate.
Another concern with using PSA for screening is that it usually necessitates a prostate biopsy to confirm the diagnosis. Despite this invasive procedure, about 75% of men with abnormal PSA levels who proceeded to have a biopsy turned out not to have any cancer.
The US Preventive Services Task Force (USPSTF) does not recommend routine PSA screening for men without symptoms. Therefore, men need not be pressured to take a PSA test, unless they are above 50 years old, have lower urinary tract symptoms, and have a family history of prostate cancer.
If you are unsure whether you fall into this category, ask your doctor. You should discuss your risk factors and prostate symptoms (if any) with the doctor, and the potential harm of screening.
Do not trust anyone who claims that you can diagnose prostate cancer from a PSA test alone.
The members of the MMHI are Prof Dr Tan Hui Meng, Assoc Prof Dr Ng Chirk Jenn, Prof Dr Low Wah Yun, Prof Dr Khoo Ee Ming, Assoc Prof Dr Tong Seng Fah, Dr Verna Lee Kar Mun, Dr Lee Boon Cheok, Prof Dr George Lee Eng Geap, Assoc Prof Dr Zulkifli Md. Zainuddin, Dr Christopher Ho Chee Kong, Assoc Prof Dr Ong Teng Aik, Dr Yap Piang Kian and Dr Goh Eng Hong. For further information, e-mail email@example.com. The information provided is for educational and communication purposes only and it should not be construed as personal medical advice. Information published in this article is not intended to replace, supplant or augment a consultation with a health professional regarding the reader’s own medical care. The Star does not give any warranty on accuracy, completeness, functionality, usefulness or other assurances as to the content appearing in this column. The Star disclaims all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.
If you want to learn more about the prostate, you can get a copy of “Men’s Health and The Prostate” published by MMHI, available at RM45 each. To obtain copies, contact Ms Poh or Mr Teo at 03-56391777; fax: 03-56391870; email:firstname.lastname@example.org. Proceeds from the sale of this book go towards the research funds of the Malaysian Society of Andrology and The Study of The Aging Male. The book can be delivered to any address within Malaysia by mail or courier without any additional charge.