Prostate cancer is the second most commonly diagnosed cancer and the fifth leading cause ofcancer death in men. The life time risk of developing prostate cancer is 16% and the risk of dying from prostate cancer is about 3%.
The problem is prostate cancer grows so slowly that most men die of other causes before the disease becomes clinically advanced. This is why I wanted to talk to you about prostate screening – the good, the bad, the ugly.
The PSA was initially used as a tumor marker to detect cancer recurrence and/or disease progression after treatment. In the 1990s recommendations were then made to use PSA as a method of screening.
Screening is controversial. There have been multiple papers published stating that no benefit can be had with routine screening of prostate cancer with PSA and digital rectal exam after 10 years follow up. An elevated PSA will lead to biopsy which often leads to diagnosing clinically unimportant cancers.
There is also a significant reduction in the quality of life once a cancer is diagnosed including erectile dysfunction, urinary incontinence, and bowel problems. This is due to the aggressive treatments which are instituted.
PSA can be elevated 5-10 years before prostate cancer is clinically evident. But, other things can elevate the PSA as well: BPH, prostatitis, inflammation, prostate biopsy, rectal exams, trauma, urinary retention, and ejaculation.
The five-alpha reductase inhibitors (finasteride) lowers PSA levels by up to 50% after 6 months of use. Some experts recommend doubling the levels for patients on these medications.
Prostate biopsy can have a false negative rate of up to 20% – which is why 12 samples are taken when biopsy is needed.
Current recommendations put the PSA cut off value at 4. It’s thought that 30% of men who have a PSA over 4 will have cancer found on biopsy. The numbers go to about 50% with levels over 10. But after a value of 10 the chance that the cancer is only confined to the prostate decreases – making these cancers incurable.
It’s also important to note that prostate cancer (high grade and with elevated gleason scroes) can also be diagnosed in patients who have a PSA less than 4.
The Prostate Cancer Prevention Trial found that for biopsies performed during follow-up in the control group even a PSA cutoff of 1.1 ng/mL would miss 17 percent of cancers.
There is also some evidence that states diagnosing cancers with a low PSA value will not affect outcomes.
PSA velocity (change in PSA over time), PSA density (PSA per unit volume of prostate), free PSA, complexed PSA, and using age- and race-specific reference ranges have all been suggested to improve the accuracy of PSA – but are not routinely recommended because none have been shown to reduce the number of unnecessary biopsies or improve clinical outcomes.
When performing the exam, the clinician is palpating for nodules, asymmetry, and/or induration. These findings are only present when the cancer grows peripherally (which is only 85% of the time). Stage T1 cancers are nonpalpable by definition.
There is no reduction in morbidity or mortality when performing DRE. Most cancers detected by DRE are far too advanced.
Up to 40% of cancers will be missed if ultrasound is used as a screening test. TRUS should be used to guide prostate biopsy only.
Harm from screening
Biopsy comes with the risk of bleeding and infection – some patients are even hospitalized due to infection. Pain can also be noted after the biopsy – some patients report pain even a week afterwards.
Overdiagnosis is also a problem. Not only will some of these cancers never become clinically significant – but being diagnosed with cancer increases the incidence of anxiety and depression in patients. Autopsies have reported a 30%-45% prevalence of prostate cancer in men who are in their 50s and an 80% prevalence of prostate cancer in men who were in their 80s at the time of death who died from other causes.
It’s currently believed that 30% of prostate cancers are overdiagnosed.
This also means therapy (radiation and radical prostatectomy) will be started after diagnosis – which carries it’s own risks.
It has been proven that universal screening should be avoided. But, the decision to screen should be the patients. The conversation should begin at 50 years of age who have a life expectancy over 10 years.
Screening is done with PSA testing alone without DRE. Testing frequency isn’t agreed upon. Some authorities say to test every year, 2 years, or 4 years. If the PSA is over 2.5 then annual screeningshould be strongly considered.
Screening can be stopped after 70 and/or when there is a life expectancy less than 10 years.
If DRE is done and if nodules, induration, or asymmetry are felt then patients should be referred for biopsy. Patients with a PSA over 7 should be referred for biopsy.
If the PSA is between 4-7 then it might be best to repeat the PSA 4 weeks later. If the PSA continues to be elevated then refer for biopsy. Before repeat testing patients should abstain from sex and from activities of potential trauma (bike riding) for 48 hours before testing.
If the biopsy is positive then the cancer is staged. If the biopsy is negative then routine screeningshould be resumed or possibly referred for repeat biopsy due to false negatives. One study in particular found prostate cancer in 20% of patients on repeat biopsy testing after an initial negative biopsy.