PSA, So What?

The PSA test is not liked by many. Why? Because it often finds indolent cancers. Thus many entities want to ban its use. Is that a good idea? Not really but here is the latest.

From Cancer Research UK they note:

The potential for blood tests that detect cancer is huge. But what if a test is, in some ways, too good? What if it finds cancers that if left undetected wouldn’t cause a person any harm? And what if it’s not possible to know for certain which cancers need to be treated, or who could avoid a life-altering diagnosis and potential long-term treatment side effects? This is the situation right now with prostate cancer. There’s no UK screening programme for prostate cancer. That’s because the blood test that would be used – called the PSA (or prostate specific antigen) test – isn’t reliable enough.
Men over the age of 50 with no symptoms of prostate cancer can still ask for the test in the UK. But its use is hotly debated around the world. Now, a new Cancer Research UK-funded study, from scientists at the Universities of Bristol and Oxford, sheds more light on how unreliable the test is. And it confirms that for men without symptoms, the PSA test doesn’t save lives.

 Now from the referrd to JAMA paper it notes:

In the intervention group, men aged 50 to 69 years received a single invitation to a nurse-led clinic appointment. At the appointment, men were provided with information about PSA testing. After giving consent, men were offered the PSA test. Men with PSA levels of 3.0 ng/mL or greater were offered a standardized 10-core transrectal ultrasound–guided biopsy. Those diagnosed with clinically localized prostate cancer and who met the eligibility criteria were recruited to participate in the ProtecT trial to receive treatment. The ProtecT trial compared radical prostatectomy, radical conformal radiotherapy with neoadjuvant androgen deprivation therapy, and active monitoring.⁵ In contrast, the control practices provided standard National Health Service management, and information about PSA testing was provided only to men who requested it. 

This procedure is akin to taking a single sample of blood pressure and assuming it is the same for ever! The fundamental approach to any patient is to see if anything changes over time. That was to have been the core of any electronic health record, never achieved however. A good physician looks for change, in a mole, in blood pressure, in weight, in vision, and yes in PSA!

The JAMA article concludes:

Among practices randomized to a single PSA screening intervention vs standard practice without screening, there was no significant difference in prostate cancer mortality after a median follow-up of 10 years but the detection of low-risk prostate cancer cases increased. Although longer-term follow-up is under way, the findings do not support single PSA testing for population-based screening.

 First a single measurement of anything is near useless! Second, PSA works only if measured over time and such measures as velocity and percent free are also measured. Thirdly, a ten core biopsy not guided by MRI is "shingling the roof in the fog". One has no idea what they are biopsying! No wonder there was no change in mortality.

In my opinion based upon a multiplicity of prior analyses and clinical studies, this result proves that a single PSA test is useless. That is all.