In almost all diseases, screening and early detection is the key to management and cure. What used to be fatal diagnoses of late stage breast and cervical cancer have now become uncommon as more and more cases are detected early by regular screening.
In men, prostate cancer is the third leading cause of cancer mortality. The Institute for Cancer Research (ICR) in the UK gives us the following statistics:
As many as 80% of men develop prostate cancer during their lifetime, but in most cases it does not cause any ill health. Around 6% of men experience symptoms of the disease, while 3% of men die of prostate cancer.
Screening for prostate cancer is done in two ways, namely:
PSA test. Prostate-specific antigen (PSA) is protein biomarker produced by prostate cells. PSA is normally present in blood in low amounts. Cancerous (malignant) prostate cells are expected to produce more PSA than noncancerous cells, leading to elevated PSA levels in the blood. PSA testing consists mainly of testing for levels of the antigen in a blood sample. If PSA levels are found to be high, other tests, including a prostate biopsy may be deemed necessary. Currently, the American Urologic Association, the American Cancer Society, and the National Comprehensive Cancer Network recommend that all men 50 years and older should have annual PSA tests. Men with high risk profiles (e.g. of African American heritage, family history of prostate cancer) are advised to get tested starting at the age of 40.
Digital rectal examination. This examination is performed by a doctor by inserting a lubricated finger through the rectum. Through the walls of the rectum, the doctor can feel for structural abnormalities (bumps, growths, enlargement) in the prostate.
The usefulness of the PSA test in screening for prostate cancer has always been a subject of controversy. Some studies have produced inconclusive results regarding its benefits as well as its side effects. Potential risks include, unnecessary invasive testing (biopsy), and unnecessary treatment with serious side effects, and unnecessary expense. However, 95% of male urologists and 78% of male primary care clinicians admit to having had a PSA test themselves. PSA gives the potential benefits of catching cancer at its early stages, with better prognosis.
In the March issue of the New England Journal of Medicine, results of two studies on PSA screening were presented: one study conducted in the US, and one study conducted in Europe. Unfortunately, instead of resolving the controversy once and for all, the two studies actually produced contradicting results.
The American study:
Mortality Results from a Randomized Prostate-Cancer Screening Trial
This study is part of the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. The study looked at 76,693 men from 1993 to 2001. About 50% of the participants had PSA screening every year for 6 years and digital rectal examination for 4 years. The other half did not undergo screening for prostate cancer. The PLCO results showed that after 7 to 10 years the incidence of prostate cancer was 116 per 10,000 person-years in the screening group and 95 in the control group. The incidence of death per 10,000 person-years was 2.0 (50 deaths) in the screening group and 1.7 (44 deaths) in the control group. Statistically speaking, there was no difference in cancer incidence and mortality between the screened group and the unscreened group.
The European study:
Screening and Prostate-Cancer Mortality in a Randomized European Study
The European Randomized Study of Screening for Prostate Cancer (ERSPC) started in the 1990s and followed up 182,000 men aged between 50 and 74 years old for about 12 years. The study had also two groups. In one group, PSA screening way conducted on average, once a year. The other group did not undergo PSA screening. The study was conducted in 8 European countries, namely Belgium, Finland, France, Italy, Netherlands, Spain, Sweden and Switzerland The results of the study showed that
Both studies will now look into the cost effectiveness and overall quality of life of the PSA testing. Although PSA testing itself is non-invasive, the subsequent confirmatory tests such as biopsy can be invasive and present with risks.
About PSA testing
Many experts observe that PSA testing is not specific enough and has a 30% rate of false positives – e.g. cancers are non-aggressive and are indolent or slow-growing. It is sometimes difficult to decide which really cancer needs treatment which one doesn’t. While many would opt to be on the safe side and go for early treatment, the treatment comes with side effects such as impotence and incontinence.
A more conservative form of prostate cancer monitoring is called “Active Surveillance which aims to individualise the management of early prostate cancer by selecting only those men with significant cancers for curative treatment… Patients on active surveillance are closely monitored using PSA blood tests and repeat prostate biopsies. The choice between continued observation and curative treatment is based on evidence of disease progression during this monitoring.”
It seems that prostate cancer screening by PSA testing have its pros and cons. In the end, it is always a question whether the benefits outweigh the costs.
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